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We report on the effective passivation of cut edges of n-type (100) crystalline silicon by forming thin oxide layers achieved by heat treatment in liquid water at 90 °C for 2 h followed by heating in an air atmosphere at 300 °C for 1 h. The mechanical cut with the (110) oriented cleaved edge markedly decreased the photo-induced effective minority carrier lifetime τ eff to 6.9 × 10−4 s, which was 0.22 times the initial value of 3.2 × 10−3 s, and which was maintained by the region 0.5 cm away from the edge. The present passivation treatment resulted in the reduction of τ eff to 0.43, with τ eff values of 4.0 × 10−4 s at the edge and 9.4 × 10−4 s at 0.2 cm from the edge. The analysis with a simple model of carrier diffusion in the lateral direction resulted in the recombination velocity at the cut edge, which was initially higher than 2000 cm s−1, being decreased to 50 cm s−1 by the present treatment, while the recombination velocity at the sample surface was increased from 8 (initial) to 46 cm s−1, probably due to the field-induced depletion effect.

In this study, we developed very simple and ULSI (ultra large scale integration) compatible fabrication processes for group-IV (Si1 –xGe x and Si) semiconductor quantum dots (QDs) to apply hybrid ULSIs with photonic and electron devices, using double Ge+/Si+ hot-ion implantation into a SiO2 layer with larger bandgap EG and the post-furnace annealing. We successfully demonstrated the near-infrared (IR) photoluminescence (PL) from Si1 –xGe x-QDs. Transmission electron microscopy observations of single-crystallized Si1 –xGe x-QDs revealed that the diameter and the QD density were 3.6 ± 0.9 nm and (2.6 ± 0.4) × 1012 cm−2, respectively. In addition, Ge atoms were detected in the Si1 –xGe x-QDs by the energy dispersive x-ray spectroscopy analysis, and the Ge fraction of Si1– xGe x-QDs was varied from 0.06 to 0.26 by changing the Ge ion dose. The increase in the PL intensity by forming gas annealing was attributed to the dangling-bond reduction by the H-atom termination method. The PL spectrum of Si1 –xGe x-QDs was fitted by PL components of two QD structures containing Si1 –xGe x and Si materials. The PL intensity and PL-peak photon energy of Si1 –xGe x-QDs strongly depended on the Ge fraction. The Si1 –xGe x-QDs achieved the maximum PL intensity at x ≈ 0.13. High PL-peak photon energy (∼1.31 eV) of Si1 –xGe x-QDs is attributed to the quantum confinement effect of carriers in QDs. Consequently, group-IV semiconductor QDs including Si1 –xGe x, Si, SiC, and C, through the simple hot-ion implantation into the SiO2 layer, exhibited a wide range of PL emissions from the near-IR to ultraviolet regions.

To realize uniform heating characteristic of 2.45-GHz-microwave-induced-heating system with a 330-mm-diameter heating unit of carbon heating tubes (CHTs), we installed a propeller-type-rotational antenna with two 120-mm-long blades with tilted angles of 45 and −45° and a height of 105 mm in 330-mm-diameter cavity with a modified rotating velocity optimized by the numerical simulation. The CHT heating at 800°C for 170 s reduced the sheet resistivity ranging from 60 to 80 Q/sq for 1.0×1015 cnr=phosphorus implanted 300-mm-diameter silicon substrates. The average activation ratio Pay was 0.77 and its mean square deviation PRMSD was 0.05. They were better than Pay of 0.73 and PRMSD of 0.06 in the case of the CHT heating with no antenna.

We report a microwave heating system with a carbon heating tube (CHT) which was made by a 4-mm diameter quartz tube filled with carbon particles and Ar gas at 1400 Pa. A 60-mm-long CHT was set in a cavity in which 2.45-GHz microwave was introduced. Via nearly complete absorption of a microwave power of 200 W by carbon in the CHT during multi-reflection of the microwave in the cavity, the CHT was effectively heated to 1279 °C at 33 s after the microwave initiation, which was observed by the radiation-type thermometer. Moreover, the control of the CHT temperature was demonstrated with a home-made proportional–integral–differential feedback circuit which regulated the magnetron power source using a signal of the thermometer. The control of temperature at 1100 °C was successfully realized. Crystallization of a 58-nm-thick amorphous silicon thin film formed on the glass substrate was demonstrated by mechanically moving the silicon sample just below the heated CHT. A high crystalline volume ratio of 0.92 was achieved. Furthermore, heating of 500- $\mu \text{m}$ -thick-n-type silicon substrate implanted with $1.0\times 10^{15}$ cm−2 phosphorus and boron atoms with the CHT resulted in activation of the doped regions. Rectified diode characteristics were achieved.

We report 2.45-GHz-microwave-induced heating system with carbon heating tubes (CHTs) which consists of 330-mm-long quartz tube filled with carbon particles and Ar gas. A metal cavity was developed to effectively introduce microwave to CHTs. Numerical calculation demonstrates effective absorption of microwave by CHTs placed in the cavity with 330 mm diameter. Heating CHTs with 200 S/m above 1000°C was experimentally demonstrated. 1.0x1015-cm−2 phosphorus implanted surface regions in crystalline silicon were activated and the sheet resistivity was decreased to 78 Ω/sq with an activation ratio of 80%. The photo-induced effective minority carrier lifetime increased to 120µs because of reduction of defect induced by ion implantation.

We experimentally studied the influence of both impurity density and dangling-bond density on PL emissions from group-IV-semiconductor quantum-dots (IV-QDs) of Si and SiC fabricated by hot-ion implantation technique, to improve the PL intensity (I PL) from IV-QDs embedded in two types of insulators of quartz-glass (QZ) with low impurity density and thermal-oxide (OX) layers. First, we verified the I PL reduction in the IV-QDs in QZ. However, we demonstrated the I PL enhancement of IV-QDs in doped QZ, which is attributable to multiple-level emission owing to acceptor and donor ion implantations into QZ. Secondly, we confirmed the large I PL enhancement of IV-QDs in QZ and OX, owing to forming-gas annealing with H2/N2 mixed gas, which are attributable to the reduction of the dangling-bond density in IV-QDs. Consequently, it is possible to improve the I PL of IV-QDs by increasing impurity density and reducing dangling-bond density.

We report a microwave heating system with a carbon heating tube (CHT) made by a 4-mm diameter quartz tube filled carbon particles and Ar gas at 1400 Pa. 2.45-GHz microwave at 200 W was introduced to a 300-dimameter metal cavity, in which 60-mm-long CHT was set at the central position. The numerical simulation with a finite element moment method resulted in the standing wave of the electric field caused by three dimensional Fresnel interference effect with low high electric field intensity ranging from from 1 to 6 kV/m because of effective absorption of microwave power by the CHT. The lowest average electrical field intensity of 5 kV/m in the cavity space was given by the electrical conductivity of carbon ranging from 10 to 55 S/m. The CHT with 55 S/m heated to 1200oC by microwave irradiation at 200 W. This heating method was applied to activate 1.0x1015-cm-2 boron and phosphorus implanted regions in n-type crystalline silicon substrate to fabricate pn junction and solar cells. The CHT heating at 1200oC realized decrease in the sheet resistivity to 146 Ω/sq, decrease in the density of defect states to 1.3x1011 and 9.2x1010 cm-2 for boron (p+) and phosphorus (n+) implanted surfaces, and solar cell characteristic with a conversion efficiency of 15% under illumination of air mass 1.5 at 0.1 W/cm2.

We report formation of low resistivity n-type doped silicon region at 300°C by the method of two-step ion implantation. Phosphorus ions with a dose of 2×1014 cm−2 at 70 keV followed by hydrogen ions with 1×1016 cm−2 at 8 keV were implanted at RT to the both surfaces of single crystalline silicon substrates. Post heating at 300°C for 90 min decreased the sheet resistivity to 417 Ω/sq. The activation ratio was estimated as 75% under the assumption of electron mobility of 50 cm2/Vs in the doped region. Moreover, the minority carrier effective lifetime (τ eff ) was also increased to 253 μs. This indicates a low density of surface recombination defect states of 6.4×1010 cm−2. In contrast, a high sheet resistivity of 8×104 Ω/sq and a low τ eff of 64 μs resulted from a single phosphorus ion implantation with 2×1014 cm−2 at 70 keV followed by 300°C heating for 90 min. The hydrogen ion implantation probably decreased the silicon bonding energy to easily move phosphorus atoms in the silicon lattice sites at 300°C and passivated the doped region by terminating silicon dangling bonds.

We report 2.45-GHz microwave heating system with a carbon heating tube (CHT) made by a 4-mm-diameter and 60-mm-long-quartz tube filled with conductive carbon particles and Ar gas at 1400 Pa set in a 300-mm-diameter-sized metal cavity. The three-dimensional finite element numerical simulation method resulted in the most effective electrical conductivity of CHT ranged from 10 to 55 S/m to absorb the microwave power. A proportional-integral-differential feedback CHT temperature control system was used to activate 1.0×1015-cm−2-boron and phosphorus implanted regions in n-type crystalline silicon substrate from 1000 to 1200°C. The CHT heating at 1200°C realized decrease in the sheet resistivity to 146 Ω/sq, decrease in the density of defect states to 1.3×1011 and 9.2×1010 cm−2 for boron (p+) and phosphorus (n+) implanted surfaces, and solar cell characteristic with a conversion efficiency of 15% under illumination of air mass 1.5 at 0.1 W/cm2.

We experimentally studied the Si surface orientation dependence of SiC nano-dot formation in a hot-C+-ion implanted bulk-Si substrate (C+-bulk Si), to analyze the effects of Si atom surface density on SiC nano-dot formation in Si and the photoluminescence (PL) property. We successfully demonstrated SiC dot formation even in (110) and (111) C+-bulk Si, too. SiC dot size and density of (110) C+-bulk Si is larger than those of (100) C+-bulk Si. The photoluminescence (PL) properties of C+-bulk Si strongly depend on the Si surface orientation, and the PL intensity is the minimum in (110) C+-bulk Si with lowest Si atom surface density.

We experimentally studied three types of group-IV-semiconductor quantum-dots (IV-QDs) of Si-, SiC-, and C-QDs in a thermal SiO2 layer that were fabricated using a very simple hot-ion implantation technique for Si+, double Si+/C+, and C+ into the SiO2 layer, respectively, to realize a different wavelength photoluminescence (PL) emission from near-IR to near-UV ranges. TEM analyses newly confirmed both Si- and C-QDs with a diameter of approximately 2–4 nm in addition to SiC-QDs in SiO2. We successfully demonstrated very strong PL emission from three IV-QDs, and the peak photon energies (E PH) (peak PL-wavelength) of Si-, and SiC-, and C-QDs were approximately 1.56 eV (800 nm), 2.5 eV (500 nm), and 3.3 eV (380 nm), respectively. IV-QDs showed that the PL properties strongly depend on the hot-ion doses of Si and C atoms and the post N2 annealing processes. Consequently, it is easy to design peak PL wavelengths by controlling the ion doses of Si+ and C+ implanted into the SiO2 layer.

We experimentally studied the material structure and photoluminescence (PL) properties of SiC quantum-dots (QD) in SiO2 layer (Si+/C+–OX) fabricated by double hot-Si+/C+ ion implantation into SiO2 and the post N2 annealing, comparing with those of SiC-dots by single hot-C+ ion implanted oxide (C+–OX) and crystal-Si layers (C+–Si). X-ray photoemission spectroscopy for Si+/C+–OX confirmed Si–C bonds even in SiO2, which is the direct verification of SiC formation in SiO2. Moreover, transmission electron microscope analyzes showed that 2 nm diameter SiC-dots with a clear lattice spots were successfully formed in Si+/C+–OX. After N2 annealing, we demonstrated strong PL emission from Si+/C+–OX, and the PL intensity I PL of Si+/C+–OX is approximately 2.6 and 12 times larger than those of C+–Si and C+–OX, respectively. The stronger I PL of Si+/C+–OX is possibly attributable to QD-induced PL-efficiency enhancement in Si+/C+–OX. Moreover, PL photon energy at the peak I PL of Si+/C+–OX rapidly increases to approximately 2.4 eV after N2 annealing.

The H+ or Ar+ precursor implantation at room temperature (RT) was proposed to activate boron atoms subsequently implanted in single crystalline silicon by post heating at a low temperature. The two-step ion implantation of 1.5×1016 cm−2 H+ at 8 keV followed by 1.0×1015 cm−2 B+ at 40 keV for both surfaces of silicon and 1.0×1014 cm−2 Ar+ at 70 keV followed by 1.0×1015 cm−2 B+ at 40 keV resulted in low sheet resistivities of 520 and 890 Ω/sq, respectively by post heating at 300°C for 30 min. Their activation ratios were estimated as 22 and 13%. The optimization of the projected ranges of 79 nm for 6×1013 cm−2 Ar+ at 70 keV and of 46 nm for B+ at 10 keV further decreased the sheet resistivity to 392 Ω/sq and increased the activation ratio to 29.5%. The activation of B+ implanted region at 300°C probably resulted from a decrease in the activation energy induced by a decrease in the silicon bonding energy promoted by the first H+ or Ar+ precursor implantation.

Heat treatment in liquid water at 80°C well passivated the surfaces of 20-Ωcm p-type crystalline silicon substrate and a high photo-induced minority carrier lifetime, τ eff of 4.0×10−5 s was obtained. 100-nm-thick SiO 2 layers were formed on the liquid water passivated surfaces at 300°C by the plasma chemical vapor deposition method to form the metal-oxide-semiconductor (MOS) structure. The MOS samples were subsequently annealed at 300°C for 1 h. The high frequency capacitance response with the bias voltage (C-V) measurement resulted in a threshold voltage, a density of interface defects, and a density of fixed charge as −0.35 V, 2.2×1011 cm−2eV−1, and 1.1×1011 cm−2, respectively, while they were −9.7 V, 1.4×1012 cm−2eV−1, and 2.3×1012 cm−2 in the case of no liquid water heat treatment.

We report a new heating system with a carbon heating tube (CHT) which was made by a quartz tube filled with carbon particles and Ar gas. A 60-mm long and 4-mm diameter CHT was set in a cavity in which 2.45-GHz microwave was introduced. Via complete absorption of the input microwave power by carbon in the CHT during multi-reflection of microwave in the cavity, the CHT was effectively heated to 1279°C at a microwave power of 200 W for 33 s. Crystallization of a 50-nm-thick amorphous silicon thin film formed on glass substrate was demonstrated by mechanically moving the silicon sample just below the heated CHT. A high crystalline volume ratio of 0.9 was achieved.

Ion implantation of 1.5xl016-cm−2 H+ at 8 keV or 1.0xl014-cm−2 Ar+ at 70 keV was carried out at room temperature (RT) to crystalline silicon in advance of ion implantation of 1.0×10-15-cm−2B+ at RT. Decrease in the crystalline volume ratio and generation of crystalline defects were promoted by the first H+ or Ar+ implantation. Subsequently post heating at 300°C for 30 min decreased the sheet resistivity to 520 and 890 Ω/sq in the cases of the H+ and Ar+ implantation, respectively. The decreases in the sheet resistivity by 300°C post annealing is interpreted that formation of crystalline defects by the first H+ or Ar+ implantation decreased the activation energy for moving boron atoms from the interstitial to lattice sites and achieved carrier generation at the low temperature.

Activation and carrier generation are reported in the case of phosphorus implantation with a dose of 2.0 × 1015 cm−2 at 70 keV to crystalline silicon substrates under heating ranging from 200 to 500 °C. The analysis of the optical reflectivity spectra of implanted surfaces revealed that the effective amorphized thickness was low of 2.9 nm in the case of 200 °C-phosphorus implantation, while it was large of 140 nm for implantation at room temperature. The carrier density par unit area increased from 6.9 × 1013 to 4.8 × 1014 cm−2 and the photo-induced minority carrier effective lifetime increased from 2.2 × 10−6 to 1.6 × 10−4 s as the implantation temperature increased from 200 to 500 °C. Defect reduction with 1.3 MPa H2O vapor heating at 250 °C for 3 h increased the carrier density par unit area of the 200 °C-phosphorus-implanted sample to 2.7 × 1014 cm−2. The rectified characteristics were obtained by current–voltage measurement in the case of phosphorus implantation to p-type silicon substrate. Photovoltaic effect was also observed. These results show that the ion implantation under low temperature heating has a capability of p–n junction formation.

13.56 MHz capacitance coupled Ar plasma irradiation at 50 W for 120 s caused serious damage at SiO2/Si interfaces for n-type 500-μm-thick silicon substrates. The 635-nm-light induced minority carrier effective lifetime (τeff) was decreased from 1.7 × 10−3 (initial) to 1.0 × 10−5 s by Ar plasma irradiation. Moreover, the capacitance response at 1 MHz alternative voltage as a function of the bias voltage (C–V) was changed to hysteresis characteristic associated with the density of charge injection type interface traps at the mid gap (Dit) at 9.1 × 1011 cm−2 eV−1. Subsequent 940-nm laser annealing at 3.7 × 104 W/cm2 for 4.0 × 10−3 s markedly increased τeff to 1.7 × 10−3 s and decreased Dit to 2.1 × 1010 cm−2 eV−1. The hysteresis phenomenon was reduced in C–V characteristics. Laser annealing effectively decreased the density of plasma induced carrier recombination and trap states. However, laser annealing with a high power intensity of 4.0 × 104 W/cm2 seriously caused a thermal damage associated with a low τeff and a high Dit with no hysteresis characteristic.

We report effective passivation of silicon surfaces by heating single crystalline silicon substrates in liquid water at 110°C for 1 h. High values of photo-induced effective minority carrier lifetime τeff in the range from 1.9x10-4 to 1.8x10-3 s were obtained for the n-type samples with resistivity in the range from 1.7 to 18.1 Ωcm. τeff ranged from 8.3x10-4 to 3.1x10-3 s and from 1.2x10-4 to 6.0x10-4 s over the area of 4 inch sized 17.0 Ωcm n- and 15.0 Ωcm p-type samples, respectively. The heat treatment in liquid water at 110°C for 1 h resulted in low surface recombination velocities ranging from 7 to 34 cm/s and from 49 to 250 cm/s for those 4 inch sized n- and p-type samples, respectively. The thickness of the passivation layer was estimated to be approximate only 0.7 nm. Metal-insulator-semiconductor type solar cell was demonstrated with Al and Au metal formation on the passivated surface. Rectified current voltage and solar cell characteristics were observed. Open circuit voltage of 0.47 V was obtained under AM 1.5 light illumination at 100 mW/cm2.

We report rapid laser-induced passivation of the silicon surface. When the top surfaces of n-type 500-µm-thick silicon substrates with surfaces coated with 100 nm thermally grown SiO2 layers (initial samples) were irradiated with Ar plasma at 50 W for 120 s, the 635-nm-light induced minority carrier effective lifetime τeff decreased from 1.7x10 -3 (initial) to 1.7x10 -5 s because Ar plasma caused substantial carrier recombination defect states at the silicon surfaces. τeff was markedly increased to 1.7x10 -3 s by 940-nm-semiconductor laser irradiation at 3.57x10 4 W/cm 2 for 4 ms. Laser heating effectively decreased the density of plasma induced carrier recombination defect. However, laser heating of the initial sample at 4.0x10 4 W/cm 2 decreased τeff from 2.2x10 -3 (initial) to 1.7x10 -4 s. Additional laser heating at 3.70x10 4 W/cm 2 increased τeff to 3.9x10 -4 s and it partially cured laser in

We report connection conductivity ( $$C_{\rm c}$$ ) of adhesive which including $$\hbox {In}_2\hbox {O}_3$$ – $$\hbox {SnO}_2$$ (ITO) particles developed for fabrication of stacked-type-multi-junction solar cells. The commercial 20- $$\upmu $$ m sized ITO particles were heated in vacuum at temperature ranging from 800 to 1,300 $$^{\circ }{\rm C}$$ for 10 min to increase $$C_{\rm c}$$ . 6.2 wt% ITO particles were dispersed in commercial Cemedine adhesive gel to form 100 samples structured with n-type Si/adhesive/n-type Si (n-Si sample) and p-type Si/adhesive/p-type Si (p-Si sample). Current density as a function of voltage (J–V) characteristics gave $$C_{\rm c}$$ . It ranged from 4.3 to 1.0 S/cm $$^2$$ for the n-Si sample with 800 $$^{\circ }{\rm C}$$ heat-treated ITO particles. Its standard deviation was 0.59 S/cm $$^2$$ . On the other hand, it ranged from 2.0 to 0.6 S/cm $$^2$$ for the p-Si sample with 800 $$^{\circ }{\rm C}$$ heat-treated ITO particles. Its standard deviation was 0.22 S/cm $$^2$$ . The distribution of $$C_{\rm c}$$ mainly resulted from contact efficiency of ITO particles to substrate. We theoretically estimated that present $$C_{\rm c}$$ achieved a low loss of the power conversion efficiency ( $$E_{\rm ff}$$ ) lower than 0.3 % in the application of fabrication of multi-junction solar cell with an intrinsic $$E_{\rm ff}$$ of 30 % and an open circuit voltage above 1.9 V.

We report a mechanical stacking technology with transparent conductive adhesive as intermediate conductive layer for multi-junction-solar cells. Transparent adhesive jell dispersed with Indium-Tin-Oxide (ITO) particles ranging from 5 to 10 wt% was developed for stacking solar cell substrates. A connecting resistivity below 2.0 Ωcm2 was achieved in a condition of solidifying the adhesive gel under a gas pressure from 4.0x105 to 7.0x105 Pa. The connecting resistivity was kept lower than 3.0 Ωcm2 when samples was exposed at a high temperature at 80oC and a high humidity of 85% humidity atmosphere in the case of solidification pressure at 7.0x105 Pa. The low connecting resistivity give a possibility of application our conductive adhesive to solar cell with an effective efficiency higher than 30%. Stacked solar cells was successfully achieved by pasting a InGaP/GaAs thin film epitaxial layer to a Ge solar cell using our intermediate adhesive layer.

We experimentally studied SiC nano-dot formation in a bulk-Si substrate fabricated by the very simple processes of a hot-C+-ion implantation into (100) bulk-Si substrate and the following N2-annealing, and the photoluminescence (PL) properties for a future Si-based photonic device. We confirmed by a transmission electron microscope that cubic and hexagonal SiC dots are formed in a C+-ion implanted Si layer, and the SiC dot diameter (3–7 nm) and density (1–2 × 1012 cm−2) depend on the process conditions. We also observed very strong PL-intensity after N2-annealing, and the broad PL spectrum can be fitted by the sum of the PL-emissions from four different cubic and hexagonal SiC-polytypes with different exciton bandgaps. The PL-properties strongly depend on the N2-annealing temperature, and hot-C+-ion implantation temperature and dose. Consequently, we successfully optimize the process conditions to improve PL-intensity, as well as to control the PL-spectrum line shape in the near-UV/visible regions.

We experimentally studied SiC nanodot formation in an amorphous-Si (a-Si) and poly-Si on quartz substrates, using a hot-C+-ion implantation technique and post-N2 annealing, compared with SiC-dots in a (100) crystal-Si (c-Si) on insulator substrate. Even in the poor crystal quality substrates of the C+-ion implanted in a-Si and poly-Si layers, we experimentally verified 3C-SiC dot formation by transmission electron microscopy, and the strong photoluminescence (PL) intensity in the near-UV-vis regions, because a-Si is partially poly-crystallized by the high-temperature processes of hot-C+-ion implantation and post-N2 annealing. The PL spectral line shape strongly depends on the Si crystal structures, but the peak PL intensity after N2 annealing is almost independent of the Si crystal structures. Moreover, the PL spectrum can be explained by the sum of PL emissions from different cubic and hexagonal polytypes of SiC. We clarified that the three Si crystal structures have a different contribution ratio of PL components of SiC polytypes.

We report diffusing boron and phosphorus dopant atoms in silicon with impurity sources of BOx and POx layers formed on the top surfaces of n- and p-type crystalline silicon substrates. The silicon samples with impurity sources were subsequently covered with carbon powders to effectively absorb 2.45 GHz microwave power. Microwave irradiation at 1000 W for 27 s rapidly heated the carbon powders to 1265°C. The sheet resistivity of the samples decreased to 29 and 16 Ω/sq because of boron and phosphorus doping by 29-s-microwave heating. The photo-induced minority carrier lifetime increased to 2.0×10−5 and 3.5×10−5 s by 20- and 14-s-microwave heating for the boron- and phosphorus-doped samples. Boron atoms with a concentration above 1020 cm−3 diffused 150 nm deep by 26-s-microwave heating. Achievements of diode rectified characteristics and photovoltaic effect demonstrate pn junction formation at the top surface region by the present doping method.

A high photo-induced effective minority carrier lifetime τ eff of crystalline silicon was achieved by simple heat treatment in liquid water. τ eff was 2.8×10−3 s for 15-Ωcm n-type crystalline silicon heat treated in liquid water at 120°C for 1.5 h. The τ eff for the sample treated at 90°C increased from 1.0×10−4 s (just after the treatment) to 1.7×10−3 s by keeping the sample in the air atmosphere for 700 h. τ eff maintained high values up to 1800 h. The metal-insulator-semiconductor type diodes were formed by forming Al and Au metals on the 0.7-nm-thick passivated layers. Rectified current characteristics were observed in the dark field because of the difference of the work function between Al and Au. Capacitance response with the bias voltage suggested low density of interface traps. Short circuit current density of 24.3 mA/cm2 and open circuit voltage of 0.36 V were observed in the MIS-type solar cell under the light illumination of AM 1.5 at 100 mW/cm2 to the rear surface.

A combination of the carbon-powder absorber with microwave irradiation is proposed as a rapid heat method. 2-μm-diameter carbon powders with a packing density of 0.08 effectively absorbed 2.45 GHz 1000-W-microwave and heated themselves to 1163 °C for 26 s. The present heat treatment recrystallized n-type crystalline silicon surfaces implanted with $$1.0 \times 10^{15}\hbox {-cm}^{-2}$$ -boron and phosphorus atoms with crystalline volume ratios of 0.99 and 0.93, respectively, by microwave irradiation at 1000 W for 20 s. Activation and carrier generation were simultaneously achieved with a sheet resistivity of $$62\, \Omega / \hbox {sq}$$ . A high photo-induced-carrier effective lifetime of $$1.0 \times 10^{-4}$$ s was also achieved. Typical electrical current-rectified characteristic and solar cell characteristic with an efficiency of 12.1 % under $$100\hbox{-mW/cm}^{2}\hbox{-air-mass-}1.5$$ illumination were obtained. Moreover, heat treatment with microwave irradiation at 1000 W for 22 s successfully crystallized silicon thin films with thicknesses ranging from 2.4 to 50 nm formed on quartz substrates. Nano-crystalline cluster structure with a high volume ratio of 50 % was formed in the 1.8-nm (initial 2.4-nm)-thick silicon films. Photoluminescence around 1.77 eV was observed for the 1.8-nm-thick silicon films annealed at 260 °C in $$1.3 \times 10^{6}$$ -Pa-H2O-vapor for 3 h after the microwave heating.

The simple passivation method of heat treatment in liquid water is discussed. Photo-induced effective minority carrier lifetime τ eff increased to 3.3 × 10−3 s above 110 °C for 1 h for 17-Ωcm n-type crystalline silicon. Increase in τ eff was observed ranging from 3.5 × 10−4 to 3.7 × 10−3 s for n-type silicon with resistivity ranging from 2 to 17 Ωcm. τ eff maintained high values ranging from 1.5 × 10−4 to 1.4 × 10−3 s for 1270 h. The metal-insulator-semiconductor-type diodes were formed on the top surfaces of the n-type and p-type substrates by forming Al and Au metals on the 0.7-nm-thin passivated layers. Rectified and Fowler–Nordheim current characteristics were observed in the dark field because of the difference of the work function between Al and Au. High photo-induced current density of 31.1 mA/cm2 and photovoltaic effect were observed in case of light illumination of AM 1.5 at 100 mW/cm2 to the rear surface. The recombination velocity in the regions under the metal electrode in the MIS structure was determined by lateral diffusion of photo-induced carriers. They were 1000 and 11,000 cm/s under Al and Au, respectively, in the n-type Si substrate.

article i nfo Article history: We report the rapid thermal crystallization of silicon films using infrared semiconductor laser. Carbon films were used on silicon films to absorb the laser light. Uniform crystalline regions were achieved by a line shape laser beam with a length of 20 μm. Polycrystalline silicon thin film transistors were fabricated in crystallized regions. The effective electron carrier mobility and threshold voltage were achieved to be 130 cm 2 /Vs and 0.4 V, respectively, when the crystalline volume ratio of the silicon films was 0.95.

We report improvement in characteristics of hydrogenated amorphous silicon (a-Si:H ) p-i-n structured solar cells by high-pressure H2O vapor heat treatment. a-Si:H p-i-n solar cells were formed on glass substrates coated with textured SnO2 layer. P-, i-, and n-type a-Si:H layers were subsequently formed by plasma enhanced chemical vapor deposition. Finally an indium-tin-oxide layer was coated on the n-type a-Si:H surface. Heat treatment at 210 °C with 2 × 105 Pa H2O vapor for 1 h was applied to the a-Si:H p-i-n solar cells. Electrical characteristics were measured when samples were kept in dark and illuminated with light of AM 1.5 at 100 mW/cm2. The heat treatment with H2O vapor increased fill factor (FF) and the conversion efficiency from 0.54 and 7.7% (initial) to 0.57 and 8.4%, respectively. Marked improvement in solar cell characteristics was also observed in the case of a poor a-Si:H p-i-n solar cell. FF and the conversion efficiency were increased from 0.29 and 3.2% (initial) to 0.56 and 7.7%, respectively.

Buried void layer formation in silicon substrates was achieved by hydrogen ion implantation followed by 940-nm infrared laser rapid heating. P-type silicon substrates coated with 100-nm-thick thermally grown SiO2 layers were implanted with hydrogen atoms at 5x10 15 and 3x10 16 cm -2 at 60 keV. Structural investigation with analysis of optical reflectivity spectra revealed that 3x10 16 cm -2 implantation caused a void layer with a void ratio of 0.04 at a depth of 250 nm close to the position of hydrogen peak concentration. Laser irradiation at 4.2x10 4 W/cm 2 increased the void ratio to 0.12. No void layer was observed at ion implantation stage for sample with 5x10 15 cm -2 -hydrogen atoms. Laser irradiation at 4.9x10 4 W/cm 2 formed a void layer with a void ratio of 0.013 at a depth of 255 nm.

We report formation of thin aluminum oxide AlOx films on the silicon surface by a simple method of Al metal evaporation in oxygen gas atmosphere. 520 μm thick 30-Ωcm p-type-silicon substrates with a top bare surface and a rear surface coated with 100 nm thick thermally grown SiO2 layers were prepared. AlOx films were formed on the top surfaces by Al metal evaporation up to 20 s in oxygen gas atmosphere at 0.8 Pa with a flow rate of 3 sccm. Samples were subsequently annealed with 9.0x105 Pa H2O vapor at 260°C for 3 h. Measurement of capacitance response to a modulation voltage at 500 kHz as a function of bias gate voltages C-V revealed that AlOx films had the effective oxide thickness ranging from 2.0 and 2.6 nm were formed. C-V measurements also revealed that negative fixed charges were accumulated with a density of 5x1012 cm-2 in AlOx films. Photo-induced carrier microwave absorption measurement resulted in a high minority carrier effective lifetime τeff of 3.6x10-4 s comparable to that of 4.1x10-4 s for thermally grown SiO2 passivation. Field effect passivation was probably caused by negative charges in AlOx so that the surface recombination velocity decreased to 70 cm/s. X-ray reflectivity analysis indicated that the interfacial layer like SiOx was formed between AlOx and Si substrate. High pressure H2O vapor heat annealing caused increase in the density and decrease in the thickness of AlOx layers, although it increased the density and thickness of the interfacial SiOx layer thickness. H2O vapor treatment is effective to improve the quality of nanometer thick AlOxlayer.

Change in the light-induced minority carrier effective lifetime τeff of crystalline silicon caused by rapid laser heating is reported. The top surface of n- and p-type silicon substrates with thicknesses of 520 μm coated with thermally grown SiO2 layers were heated by a 940 nm semiconductor laser for 4 ms. τeff was measured by a method of microwave absorption caused by carriers induced by 620 nm light illumination at 1.5 mW/cm2. τeff for light illumination of the top surfaces was decreased to 1.0x10-5 and 4.8x10-6 s by laser heating at 5.0x104 W/cm2 for n- and ptype 520-μm-thick silicon substrates, respectively. The decrease in τeff resulted from the generation of defect states associated with the carrier recombination velocity at the top surface region, Stop. Laser heating increased Stop to 6000 and 10000 cm/s for n- and p-type silicon samples, respectively. Heat treatment at 400oC for 4h markedly decreased Stop to 21 and 120 cm/s, respectively, for n- and p-type silicon samples heated at 5.0x104 W/cm2. Laser heating at 4.0x104 W/cm2 for 4 ms was also applied to samples treated with Ar plasma irradiation at 50 W for 60 s, which decreased τeff (top) to 2.0x10-5 s and 3.9x10-6 s for n- and p-type silicon samples, respectively. Laser heating successfully increased τeff (top) to 2.8x10-3 and 4.1x10-4 s for n- and p-type samples, respectively. Laser irradiation at 4x104 W/cm2played a role of curing recombination defect sites.

We report formation of thin silicon oxide films on the silicon surfaces by combination of oxygen radical and high pressure H2O vapor heat treatment for passivation of silicon surfaces at a low temperature. Oxygen plasma was generated by 13.56 MHz radio frequency induction-coupled remote plasma with mixed gases of O2 and Ar at 2 sccm, 2x10-2 Pa and at a power of 50 W. Oxygen radical was produced from the plasma via a metal mesh closing plasma in the reactor. The top surfaces of 20 Wcm n-type silicon substrates with the rear surface coated by thermally grown SiO2 layers were exposed by oxygen radical from 1 to 5 min to oxidize the silicon surface. The samples were subsequently annealed with 9.0x105 Pa H2O vapor heat treatment at 260oC for 3 h. The effective minority carrier lifetime estimated using photo-induced carrier microwave absorption system in the case of 635 nm light illumination at 1.5 mW/cm2 to the top surface increased from 1.3x10-4 to 5.1x10-4s as the oxygen radical treatment duration increased from 1 to 5 min. The recombination velocity decreased from 380 to 90 cm/s. 500 kHz capacitance response with bias gate voltages characteristics of metal oxide semiconductor structure resulted in the effective oxide thicknesses (EOT) ranging from 1.3 to 1.7 nm. These results indicate a capability of thin oxide formation and effective passivation of silicon surfaces at a low temperature.

We have studied new abrupt-source-relaxed/strained semiconductor-heterojunction structures for quasi-ballistic complementary-metal-oxide-semiconductor (CMOS) devices, by locally controlling the strain of a single strained semiconductor. Appling O+ ion implantation recoil energy to the strained semiconductor/buried oxide interface, Raman analysis of the strained layers indicates that we have successfully relaxed both strained-Si-on-insulator (SSOI) substrates for n-MOS and SiGe-on-insulator (SGOI) substrates for p-MOS without poly crystallizing the semiconductor layers, by optimizing O+ ion implantation conditions. As a result, it is considered that the source conduction and valence band offsets EC and EV can be realized by the energy difference in the source Si/channel-strained Si and the source-relaxed SiGe/channel-strained SiGe layers, respectively. The device simulator, considering the tunneling effects at the source heterojunction, shows that the transconductance of sub-10 nm source heterojunction MOS transistors (SHOT) continues to increase with increasing EC. Therefore, SHOT structures with the novel source heterojunction are very promising for future quasi-ballistic CMOS devices.

Technologies of polycrystalline silicon thin film transistors (poly-Si TFTs) are reviewed. Many important technologies have been developed in recent twenty years for establishing low processing temperature fabrication of poly-Si TFTs in order to use glass or plastic substrates. There have been rapid thermal annealing methods for formation of poly-Si films, defect passivation of poly-Si grain boundaries, and SiO2 formation. Structural and electrical properties of poly-Si films are also discussed. Characterization and evaluation methods are also reviewed. They are important for developing poly-Si TFTs processing. We discuss capability of TFT performance and possibility of application to electronic devices in future.

Reduction in the connecting resistivity and optical reflection loss at the intermediate region of mechanically stacked multijunction solar cells are discussed. The top and bottom substrates were bonded using an epoxy-type adhesive with dispersed transparent and conductive indium tin oxide (ITO) particles. The connecting resistivity of the intermediate layer was substantially decreased to 0.12 Ω cm2 for the stacked Si substrates with 40 nm surfaces roughened by SF6/Ar plasma irradiation. The optical reflectivity of the stacked GaAs and Si substrates was well decreased by the insertion of 130-nm-thick transparent and conductive indium gallium zinc oxide (IGZO) layers at the interfaces between the semiconductor substrates and the intermediate adhesive. The IGZO layers functioned as antireflection layers and provided high effective absorbance to the bottom Si substrates for light wavelength regions, in which the top GaAs substrate was transparent and the bottom Si substrate was opaque. The effective absorbencies at incident light angles between 0 and 50° ranged from 0.94 to 0.95 for the stacked GaAs and Si structure with IGZO layers, and from 0.80 to 0.82 for the structure without IGZO layers.

*** We report the crystallization of 40-nm-thick hydrogenated amorphous silicon films using 940nm continuous wave infrared semiconductor laser with 200 nm diameter carbon particles as photo absorption. The laser beam was focused to 100 μm diameter at the surface of carbon particles. Laser irradiation at 25 W heated the carbon surface region to about 3430 K, which was estimated by analysis of spectra of light emission caused by laser irradiation when quartz substrates were placed on the surface of carbon particles. The silicon films coated with SiO2 films were crystallized by laser irradiation for 170 μs at 25 W. The crystallization volume ratio was 0.53. Crystallization over 1.1 mm area was also demonstrated by laser irradiation at 25 W.

Laser crystallization is reviewed for the purpose of fabrication of polycrystalline silicon thin film transistors (poly-Si TFTs). Laser-induced rapid heating is important for formation of crystalline films with a low thermal budget. Reduction of electrically active defects located at grain boundaries is essential for improving electrical properties of poly-Si films and achieving poly-Si TFTs with high performances. The internal film stress is attractive to increase the carrier mobility. Recent developments in laser crystallization methods with pulsed and continuous-wave lasers are also reviewed. Control of heat flow results in crystalline grain growth in the lateral direction, which is important for fabrication of large crystalline grains. We also report an annealing method using a high-power infrared semiconductor laser. High-power lasers will be attractive for rapid formation of crystalline films over a large area and activation of silicon with impurity atoms.

The quantity of hysteresis phenomena in capacitance response for metal–oxide–semiconductor (MOS) capacitors with 100-nm-thick SiO2 films formed by the sputtering method was reduced by remote oxygen plasma treatment followed by high-pressure H2O vapor heat treatment at 150 °C. In order to determine the quantity of hysteresis phenomena in capacitance response, we defined hysteresis charge as the difference in fixed oxide charge density for round bias voltage application. As-fabricated MOS capacitor samples had a high density of hysteresis charges of 1.0×1012 cm-2. The density of hysteresis charge was not decreased by 4.7×105-Pa-H2O-vapor heat treatment at 150 °C for 3 h. On the other hand, it was markedly reduced to 1.0×1011 cm-2 by 13.56-MHz-radio frequency remote oxygen plasma treatment at 300 W and 150 °C followed by 4.7×105-Pa-H2O-vapor heat treatment at 150 °C for 3 h. Hysteresis phenomena are probably caused by a temporal electron charging up of SiO2 films.

In this paper, we propose an evaluation of the crystalline properties for the surface regions implanted with phosphorus atoms by analyzing optical reflectivity spectra. We report the recrystallization behavior of disordered amorphous regions formed by implantation using infrared laser annealing. We also report that initial phosphorus in-depth profiles are not significantly changed by laser annealing. We demonstrate an effective activation and a low electrical resistance.