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The photocurrent (PC) of hot-wall-epitaxy-grown BaIn2S4 layers was studied at different temperatures and for different photoresponse intensities. With increasing temperature, the position of the PC spectra tended to shift toward longer wavelength. These PC peaks corresponded to band-to-band transitions caused by intrinsic transitions from the valence band states to the conduction band states. Also, the bandgap variations were well matched by the equation E g(T) = E g(0) − 3.79 × 10−3 T 2/(T + 499), where E g(0) was estimated to be 3.0597 eV, 3.2301 eV, and 3.2606 eV for transitions corresponding to the valence band states Γ 4(z), Γ 5(x), and Γ 5(y), respectively. By use of the selection rule and results from the PC spectroscopy, the crystal field and the spin–orbit splitting were found to be 0.1703 and 0.0306 eV, respectively. Thus, the PC intensity gradually decreased with decreasing temperature. The decrease of PC intensity was caused by the presence of trapping centers associated with native defects in the BaIn2S4 layers. The trap level was found to be a shallow donor-level type of 20.4 meV, 1.6 meV below the conduction band. Consequently, these trap levels, which are related to native defects in BaIn2S4 layers, are believed to limit PC intensity with decreasing temperature.

ZnCdO oxide thin films have been deposited by using the radiofrequency cosputtering method to prepare ozone sensors for room-temperature operation. The sensors were fabricated in the order: electrode/sensor/glass/illuminant. The mechanisms of photo-assisted oxidation and reduction on the surface of the ZnCdO ozone sensors were investigated. Free electrons and holes were generated by exposure of the surface of the ZnCdO ozone sensor to ultraviolet light, tending to enhance surface absorption of dissociated O2 molecules and dissociation of adsorbed oxygen ions, respectively. Thereby, the sensitivity of the ZnCdO ozone sensor was increased. This photon exposure method can replace the conventional heating mode used in ozone sensors. Moreover, 405-nm light from a light-emitting diode, corresponding to photon energy of 3.061 eV, was found to assist the processes of oxidation and reduction due to the chemical reaction of the ozone gas. We present a possible route for fabrication of portable ZnCdO ozone sensors for room-temperature operation.

Cd1−xZnxO alloy layers were grown by using a radio-frequency magnetron co-sputtering system. From the X-ray diffraction measurement, the Cd1−xZnxO layers were observed to have a cubic structure until a single phase for x ≤ 0.21. However, a polycrystalline form having mixed phases was observed at x = 0.29. It seems that the high miscibility of Zn in CdO leads to a large fluctuation in phase segregation caused by the hexagonal ZnO and cubic CdO structures within CdZnO. The band gap energies of the Cd1−xZnxO layers for values of x between x = 0 and x = 0.21 were distributed from 2.574 to 2.892 eV, respectively, while the band gap energy for x = 0.29 was a value of 2.834 eV due to the polycrystallinity. From the ozone sensing measurement, the working temperature of the Cd1−xZnxO layers was found to be 200 ◦C. Thus, a sensor with x = 0.21 showed a sensitivity of S = 1.31 at 100 ppb. Furthermore, the response and the reduction times of the sensor were found to be 184 and 210 sec, respectively. From these results, we found that the Cd1−xZnxO layer has a capability for use as a new material for ozone sensing.

Wide band-gap BeZnO layers were grown on Al 2 O 3 (0 0 0 1) substrate using radio-frequency magnetron co-sputtering. The rate of Be x Zn 1− x O crystallized as a hexagonal structure was x =0.2. From the X-ray photoelectron spectroscopy measurement, the O–Zn bonds relating the crystal structure and the Be–O bonds related to the deviation of the stoichiometry in the BeZnO layer were caught at 530.4 and 531.7 eV in the O 1s spectrum, respectively. Thus, the observance on the Be 1s peak of 113.2 eV associated with the bonding Be–O indicates that the sputtered Be atoms are substituted for the host-lattice site in ZnO. This Be–O bonding shows a relatively low intense and broadening spectrum caused by large fluctuation of Be content in the BeZnO layer. From the photoluminescence and transmittance measurement, the free exciton and the neutral donor-bound exciton (D 0 , X) emissions were observed at 3.7692 and 3.7313 eV, respectively, and an average transmittance rate over 95% was achieved in a wide ultraviolet (UV)–visible region. Also, the binding energy for the (D 0 , X) emission was extracted to be 37.9 meV. Through the wide band-gap material BeZnO, we may open some possibilities for fabricating a ZnO-based UV light-emitting diode to be utilized as a barrier layer comprised of the ZnO/BeZnO quantum well structure and/or an UV light emitting material itself.

ZnO based oxide system BexZn1−xO alloy of various compositions has been successfully grown by the RF co-sputtering method. The crystallinity of the BexZn1−xO alloys has been remarkably improved after the post-annealing at 600 °C compared with the BexZn1−xO alloys post-annealed at other temperatures. The x value of the BexZn1−xO layers has been increased from 0.022 to 0.17 by adjusting the RF-power of the Be target. Also, the optical bandgap energy has been modulated from 3.2218 to 3.7978 eV, respectively. Based on our results, a bandgap bowing parameter of BexZn1−xO alloy has been extracted out to be 4.5 eV. These findings could be useful to fabricate the ZnO/BexZn1−xO quantum structures and bandgap modulation for deep ultraviolet-light-emitting diodes.

Copper gallium selenide (CuGaSe2, CGS) layers were grown by the hot wall epitaxy method. The optimum temperatures of the substrate and source for growth turned out to be 450 and 610 °C, respectively. The CGS layers were epitaxially grown along the 〈1 1 0〉 direction and consisted of Ga-rich components indicating the slight stoichiometric deviations. Based on the absorption measurement, the band-gap variation of CGS was well interpreted by the Varshni's equation. The band-gap energies at low temperatures, however, had a higher value than those of other CGS. It suggests that the band-gap increase is influenced by the slightly Ga-rich composition. From the low-temperature photoluminescence experiment, sharp and intensive free- and bound-exciton peaks were observed. By analyzing these emissions, a band diagram of the observed optical transitions was obtained. From the solar cell measurement, an 11.17% efficiency on the n-CdS/p-CGS junction was achieved.

BeZnO layers, which are new materials for ultraviolet-light-emitting devices, were grown by hybrid beam method. The mobility and the carrier concentration on the BexZn1−xO layers of x = 0.28 were confirmed to be 2.83 cm2/V s and 4.16 × 1018 cm−3, respectively. Also, the optical properties attributed to the thermal quenching phenomenon of BeZnO were analyzed by photoluminescence as a function of temperature. With increasing temperature, the intensities and the spectral widths on the localized deep-level emissions of 3.6230 eV exponentially reduced and tended to broaden, respectively. Therefore, the temperature dependences of the full width at half maximum and the intensity were explained in terms of a configuration coordinate model. The broad emissions of 3.6230 eV without any fine structure were acted by a strong electron-phonon coupling due to the interaction between the radical beryllium and the ZnO host lattice. In addition, the Frank-Condon shift was found out to be 78.9 meV with the associated phonon energy of 15 meV. Thus, the activation energy of the nonradiative emission participating in the thermal quenching process was estimated to be 48.6 meV. Consequently, its value corresponds to the thermal dissociation energy requiring for the recombination of the conduction electron from the exciting state to the ground state.

Chemical bonds of As-implanted ZnO annealed in ozone molecular (O3) ambient were analyzed through the x-ray photoelectron spectroscopy as a function of the etching depth. With the etching depth increased to 25 nm from surface, the peaks of Zn2p and O1s core levels shifted toward the low-binding energy, and the bonding formation of As 3d core level gradually varied from As2O5 to As2O3. The new peaks were observed, which were posited to high-binding energy of 4.4 eV from Zn2p and O1s core levels. Finally, the chemical bonds of As-based oxides were found to consist of Zn(AsO3)2, As2O5, and As2O3. (© 2007 WILEY -VCH Verlag GmbH & Co. KGaA, Weinheim)

This is a report on the electrical characterization of gallium nitride (GaN) nanowire (NW) p–n junction diodes. These diodes were formed by assembling n-GaN NWs on p-Si (1 0 0) substrates using alternating current (AC) dielectrophoresis (DEP). The AC DEP was optimized with a bias voltage of 15 V p−p at a frequency of 1 kHz. The hetero-junction single GaN nanowire p-n diode (n-GaN NW/p-Si) showed well-defined current rectifying behavior with a forward voltage drop of 1.2–2.0 V at a current density of 10–60 A/cm 2 . The GaN nanowire p–n diodes had a high parasite resistance in the range of >470 kΩ. We observed that these high resistances were mostly the result of the metal contacts to the n-GaN NWs. We also found that these parasite resistances were reduced by the formation of an additional capping layer on the top of the n-GaN NW as well as high temperature annealing.

Epitaxial BeZnO layers, the candidates for active barrier layers composed of the ZnO/BexZn1−xO quantum well structure, were successfully grown using the hybrid beam deposition method. The Be rate of x in the grown BexZn1−xO layer was estimated to be 0.11. The optical properties caused by the thermal quenching phenomenon of BeZnO, an ultraviolet light emitting material, were studied using the temperature dependence of photoluminescence spectra. Emission of the neutral donor-bound exciton shows a tendency to quench the intensity and extend the spectral width with increasing temperatures. This tendency is related to the phonons generated by the lattice vibration of the host material in BeZnO. These findings led us to conclude that the phonons may be participating in the quenching process.

An Mg-doped p-GaN layer was grown by the metalorganic chemical vapor deposition method. The dissociation extent of hydrogen-passivated Mg acceptors in the p-GaN layer through Mg activation annealing was estimated by using room-temperature cathodoluminescence (CL) spectroscopy. The CL measurement revealed that the CL spectra intensities tend to increase with increasing the activation annealing temperature. The sample annealed at 925 °C showed the most intense emission and the narrowest width among the emission peaks. Consequently, it was the most excellent dissociation extent of Mg–H complexes caused by the Mg activation annealing. The hole concentration under this optimum condition was 1.3×10 17 cm −3 at room temperature. The photoluminescence (PL) measurement showed a 2.8 eV band having characteristically a broad peak in heavily Mg-doped GaN at room temperature. By analyzing the PL results, we learned that this band was associated with the deep donor–acceptor pair (DAP) emission rather than with the emission caused by the transition from the conduction band to deep acceptor level. The four emission peaks in the resolved 2.8 eV band were emitted by transiting from deep donor levels of 0.14, 0.26, 0.40, and 0.62 eV below the conduction band to the shallow Mg acceptor level of 0.22 eV above the valence band.

After the CdIn 2 S 4 films grown by hot-wall epitaxy method were annealed in Cd-, S- and In-atmospheres, the point defects were investigated by using the low photoluminescence (PL) experiment. In the as-grown CdIn 2 S 4 films, the free excitons corresponding to the light hole and the heavy hole have been observed, and their splitting gap was 8.2 meV.The gap is associated with the strain caused by the lattice mismatch between the substrate and the film in the heterojunction growth. By means of thermal annealing in various atmospheres, the (D°,X) emission was observed to originate from the V S or Cd int . From this emission, the E D value of the donor impurity level is extracted to 0.1950 eV.Also, the emission between the free electrons and the acceptor holes (FA) became a dominant peak after S atmosphere treatment, and the E A value of the acceptor level is turned out to be 0.2371 eV.Thus, the origin of the FA emission is related to V Cd or S int . These PL results led us to confirm that CdIn 2 S 4 :S is converted into the optical p-type. In addition, the origin of the donor–acceptor pair emissions is caused by the recombination between donors such as V S or Cd int and acceptors such as V Cd or S int . Based on these PL results, we have schemed a new energy-level diagram of the recombination process in CdIn 2 S 4 .

Single crystals of p-CdIn2Te4 were grown by the Bridgman method without a seed crystal. From photocurrent measurements, it was found that three peaks, A, B, and C, correspond to the intrinsic transition from the valence band states of Γ7(A), Γ6(B), and Γ7(C) to the conduction band state of Γ6, respectively. The crystal field splitting and the spin orbit splitting were found to be 0.2360 and 0.1119 eV, respectively. The temperature dependence of the CdIn2Te4 band gap energy was given by Eg(T)=Eg(0)−(9.43×10−3)T2/(2676+T). The Eg(0) was calculated to be 1.4750, 1.7110, and 1.8229 eV at the valence band states of Γ7(A), Γ6(B), and Γ7(C), respectively. The band gap energy of p-CdIn2Te4 at room temperature was determined to be 1.2023 eV.

Optical properties of ZnO bulk grown by hydrothermal method were investigated on the Zn-terminated surface by using Raman scattering and photoluminescence (PL). The typical Raman peak of E 2 high mode was observed at 436.20 cm −1 . Also, the peak 576.20 cm −1 was found to correspond to the LO phonon of A 1 mode. This peak was caused by the defects of O-vacancy, Zn-interstitial, or these complexes. The PL peak positions of B- and A-excitons are shifted to the shorter-wavelength side with decreasing temperature. The obtained PL intensity of excitons was exponentially reduced and the linewidth of the B-exciton broadened with increasing temperature. This is thought to be the vibration mode of LO phonon, which may be participated in quenching process. Also, the empirical band gap was found to be E g ( T )= E g (0)− αT 2 /( β + T ), where α and β were turned out to be 5.70×10 −4 eV/K and 420 K, respectively.

The high-quality CdIn 2 S 4 epilayers on the GaAs(1 0 0) substrate were first grown by using the Hot Wall Epitaxy Method. The grown CdIn 2 S 4 epilayer was found to be the 〈1 1 0〉 direction. The optimum growth temperatures of the substrate and the source turned out to be 420°C and 630°C, respectively. From the measurement of the temperature dependence of the Hall mobility, the scattering at the high-temperature range was mainly related to the acoustic mode of lattice vibration and the scattering at the low-temperature range was most pronounced due to the impurity effect. The temperature dependence of the energy band gap on the CdIn 2 S 4 /GaAs epilayer obtained from the optical absorption measurement was found to be E g (T)=2.7116 eV −(7.65×10 −4 eV / K )T 2 /(425+T) .

We have investigated the Mg-related emissions of the p-GaN layer grown by metalorganic chemical vapor deposition using Raman scattering and photoluminescence (PL) experiment. The E2 (LO) mode in the Raman scattering was found to be the blueshift of 2.29 cm−1 in comparison with that of the undoped GaN. This may be associated with the stress increment induced by the doping of Mg. The Mg-related emissions observed in the PL results are related to the deep DAP emission due to the transitions from deep donor levels of 0.14, 0.26, 0.4, and 0.58 eV below the conduction band to the shallow Mg acceptor level of 220 meV upper the valence band. Also, the Mg-related emission localized at 2.737 eV tended to quench the intensity and extend the emission linewidth with increasing temperature. This quench process is considered to be related to the vibration mode of LO phonon. Based on the two-step quenching process model and Toyozawa’s theory, the activation energy and the average energy were estimated.

AgInS2 epilayers have been grown on a GaAs substrate by using the hot-wall epitaxy method. The temperature dependence of the band gap energy of AgInS2 is determined to be E g (T)=2.1365 eV −(9.89×10 −3 eV )T 2 /(2930+T) using the absorption spectra. The free exciton binding energy, Δcr, and Δso of the chalcopyrite AgInS2 have been found to be 0.1115, 0.1541, and 0.0129 eV, respectively. This result reveals that the Δso splitting clearly exists for the Γ5 states of the valence band in the AgInS2 epilayer.

A silver indium sulfide (AgInS 2 ) epilayer was grown by hot wall epitaxy method, which has not been reported in the literature. The grown AgInS 2 epilayer was found to be a chalcopyrite structure and evaluated to be high quality crystal. From the photocurrent measurement in the temperature range from 30 to 300 K, two peaks of A and B were only observed, whereas three peaks of A, B, and C were seen in the PC spectrum of 10 K. These peaks are ascribed to the band-to-band transition. The valence band splitting of AgInS 2 was investigated by means of the photocurrent measurement. The crystal field splitting, Δ cr , and the spin orbit splitting, Δ so , have been obtained to be 0.150 and 0.009 eV at 10 K, respectively. And the energy band gap at room temperature has been determined to be 1.868 eV. Also, the temperature dependence of the energy band gap, E g ( T ), was determined.

Hg 1− x Cd x Te (MCT) was grown by hot wall epitaxy. Prior to the MCT growth, the CdTe (1 1 1) buffer layer was grown on the GaAs substrate at the temperature of 590°C for 15 min. When the thickness of the CdTe buffer layer was 5 μm or even thicker, the full-width at half-maximum values obtained from the X-ray rocking curves were found to significantly decrease. After a good quality CdTe buffer layer was grown, the MCT epilayers were grown on the CdTe(1 1 1) /GaAs substrate at various temperatures in situ. The crystal quality for those epilayers was investigated by means of the X-ray rocking curves and the photocurrent experiment. The photoconductor characterization for the epilayers was also measured. The energy band gap of MCT was determined from the photocurrent measurement and the x composition rates from the temperature dependence of the energy band gap were also obtained.

The AgInS2 epilayers with a chalcopyrite structure grown using a hot-wall epitaxy method have been confirmed to be a high quality crystal. From the optical absorption measurement, the temperature dependence of the energy band gap on AgInS2/GaAs was found to be Eg(T)=2.1365 eV−(9.89×10−3 eV)T2/(2930+T). After the as-grown AgInS2/GaAs was annealed in AgInS2/GaAs has been investigated by using the photoluminescence (PL) at 10 K. The native defects of VAg, VS, Agint, and Sint obtained from PL measurements were classified as a donors or acceptors type AgInS2/GaAs to an optical p type. Also, we confirmed that In in AgInS2/GaAs did not form the native defects because In in AgInS2 did exist in the form of stable bonds.

We investigated the doping characteristics of Mg doped, Mg-Si co-doped, and Mg-Zn co-doped GaN films grown by metalorganic chemical vapor deposition. We have grown p-GaN film with a resistivity of 1.26 Ωcm and a hole density of 4.3 × 1017 cm−3 by means of Mg-Si co-doping technique. The Mg-Si co-doping characteristic was also explained effectively by taking advantage of the concept of competitive adsorption between Mg and Si during the growth. For Mg-Zn co-doping, p-GaN showing a low electrical resistivity (0.7 Ωcm) and a high hole concentration (8.5 × 1017 cm−3) was successfully grown without the degradation of structural quality of the film. Besides, the measured specific contact resistance for Mg-Zn co-doped GaN film is 5.0 × 10−4 cm2, which is lower value by one order of magnitude than that for only Mg doped GaN film (1.9 × 10−3Ωcm2).

Titanium oxide thin films were prepared on p-Si(l00) substrate by plasma enhanced chemical vapor deposition using high purity titanium isopropoxide and oxygen. The deposition rate was little affected by oxygen flow rate, but significantly affected by RF power, substrate temperature, carrier gas flow rate, and chamber pressure. Morphology of the film became coarser with increasing deposition time and chamber pressure, and the film showed less uniformity at high deposition rates. It was also found that the overall deposition process is controlled by heterogeneous surface reaction below 200°C., but controlled by mass transfer of reactants at higher temperatures. TiO2 films deposited at temperatures lower than 400°C was amorphous, but showed the anatase crystalline structure upon 400°C deposition. The dielectric constant was about 47 for the films post-treated by rapid-thermal annealing (RTA) at 800°C. The leakage current was about 2×10−5 A/cm2 for the films deposited at 400°C and RTA-treated at 600°C. However, it was decreased to less than 3×10−7 A/cm2 for the film RTA-treated at 800°C.

A theoretical description of the kinetic mechanism of thermal oxidation in silicon is proposed by complementing the Deal - Grove model. The relationship of the classical linear - parabolic growth law is generalized to the logarithmic growth law which provides a complete description for the whole regime of oxide films. In particular, the enhanced oxidation rate in the thin regime may be attributed to the diffusion length, which is characterized by the difference between the activation energies of the diffusion process and the reaction process. Our fitting of the logarithmic growth law to several experimental results shows excellent agreement and the fitting parameters also provide activation energies of 1.50 and 2.49 eV for the interfacial reaction and diffusion in oxide respectively.

ZnO based oxide system ZnxCd1−xO alloy of various compositions has been successfully grown by the RF co‐sputtering system. ZnxCd1−xO alloy films, which have x = 0, 0.01, 0.02, 0.05, 0.08, 0.13 and 1, were grown on Al2O3 substrate. From the XRD measurement, the ZnxCd1−xO films observed to be hexagonal structure at the range of 0≤x≤0.08. At x = 0.13, the mixed crystalline of the hexagonal‐cubic structure was measured. Also, the optical bandgap energy has been modulated from 3.3 eV to 2.4 eV. After post‐Annealing, the crystallinity of the ZnxCd1−xO films improved. Furthermore, this process suggests that it is very important to maintain the optical performance for LED and LD devices.

The temperature-dependent photoresponse behavior of BaAl2Se4 layers has been investigated through the analysis of optical absorption and photocurrent (PC) spectra. Based on these results, the optical band gap was well expressed by Eg(T) = Eg(0) − 4.39 × 10−4T2/(T + 250), where Eg(0) is estimated to be 3.4205, 3.6234, and 3.8388 eV for the transitions corresponding to the valence band states Γ3(A), Γ4(B), and Γ5(C), respectively. From the PC measurement, three peaks A, B, and C corresponded with the intrinsic transitions from the valence band states of Γ3(A), Γ4(B), and Γ5(C) to the conduction band state of Γ1, respectively. According to the selection rule, the crystal field and spin orbit splitting were found to be 0.2029 and 0.2154 eV, respectively, through the direct use of PC spectroscopy. However, the PC intensities decreased with lowering temperature. In the log Jph versus 1/T plot, the dominant trap level at the high-temperature region was observed and its value was 12.7 meV. This level corresponds ...

Hydrogenated amorphous silicon films were deposited on the unstrained and strained Si substrates by an electron cyclotron resonance plasma source. The photoluminescence spectra show that emission energies are different from each other. The redshift of photoluminescence induced by the biaxial tensile stress is increased with decreasing the temperature in the range of 0.11–0.17 eV. The stress effect also enhances the quantum efficiency significantly. The pseudomorphic growth of Si on a relaxed Si0.75Ge0.25 (100) surface provides the strain energy of about 0.17 eV. These comparable results indicate that the shift of emission energy is attributed to the stress effect perturbing the polysilane structure.

Highly split, visible light emissions at room temperature were observed in the range from 335 to 650 nm in silicon‐rich oxide filmsdeposited in the plasma phase of a mixture of silane and oxygen. The mechanism of the light emissions is classified into two categories. The photoluminescence bands at both 365 and 469 nm are related to the intrinsic defects of the E′ center and the neutral oxygen vacancy, respectively. However, the relatively sharp peaks at 403 and 535 nm are correlated with the development of polycrystalline core of Si‐enriched parts.

P-doped ZnO was fabricated by means of the ion-implantation method. At the Raman measurement, the blue shift of the E2high mode and A1(LO) phonon of the inactive mode were observed after the P-ion implantation. It suggested to be caused by the compressive stress. Thus, Hall effect measurement indicates that the acceptor levels exists in P-doped ZnO while still maintaining n-type ZnO. From the X-ray photoelectron spectroscopy, the chemical bond formation of the P2p3/2 spectrum consisted of 2(P2O5) molecules. Therefore, the implanted P ions were substituted to the Zn site in ZnO. From the photoluminescence (PL) spectra, P-related PL peaks were observed in the energy ranges of 3.1 and 3.5 eV, and its origin was analyzed at PZn-2VZn complexes, acting as a shallow acceptor. With increasing temperatures, the neutral-acceptor bound-exciton emission, (A0, X), shows a tendency to quench the intensity and extend the emission linewidth. From the relations of the intensity and the linewidth as a function of temperatu...

The possible nature of metastable capture centers giving rise to persist photoconductivity (PPC) effect in As-doped p-ZnO was investigated using the photoluminescence result. Through the plot of log σph vs. 1/T and temperature-dependent PPC-decay process, the metastable trapping centers were extracted to be 15.1, 178.2, 180.6, and 291.9 meV. The shallow level of 15.1 meV was related to the binding energy of the neutral acceptor bound exciton. Also, the deep levels of 178.2 and 180.6 meV were caused by complex acceptor states of AsZn-2VZn located at 185 meV above the edge of the valence band. Furthermore, the trapping center of 291.9 meV was corresponded to the hole capture barrier of VZn located at 300 meV above the valence band. Therefore, these trapping centers were deeply related to the AX centers originating the native defects due to VZn or defect complexes of the As-implanted dopant in ZnO. Also, these defects, induced by the metastable AX centers, were concluded to be responsible for the PPC effect.

Temperature-dependent photoresponse variation on the CuAlSe2 layers was investigated by photocurrent (PC) spectroscopy as a function of temperature. Three peaks of A, B, and C caused by the band-to-band transition were observed. From these PC peaks, the temperature-dependent band-gap energy was well described by Eg(T) = 2.8382 − (8.68 × 10−4)T2/(155 + T). Thus, the parameter of the split valence band on CuAlSe2 was directly extracted out by means of the PC spectroscopy. The crystal field splitting and the spin-orbit splitting were estimated to be 0.1641 and 0.1778 eV at 10 K, respectively. However, the PC intensities decreased with decreasing temperature. It is against our expectation that the PC intensities increase with decreasing temperature. From the relation of log Jph versus 1/T, where Jph is the PC density, two dominant levels were observed, one at high temperatures and the other at low temperatures. We found out that the activation energy of 48.8 meV at high temperatures is related to the binding ...

The photocurrent (PC) variation in photoconductive CuGaSe2 (CGS) layers had been investigated as a function of temperature. Three peaks A, B, and C of the PC spectra were associated with the band-to-band transitions. Thus, the parameters of the crystal-field splitting (Δcr) and spin-orbit splitting (Δso) were directly acquired through the PC measurement. The Δcr and Δso were 0.0903 eV and 0.2130 eV at 10 K, respectively. From the relations of peak position and temperature, the temperature dependence of the band-gap energy is well described by Eg(T)=Eg(0)−(8.63×10−4)T2/(336+T). Also, the Eg(0) is estimated to be 1.7952, 1.8855, and 2.0985 eV at the valence-band states of Γ7(A), Γ6(B), and Γ7(C), respectively. However, the behavior of the PC was different from that generally observed in other semiconductors, the PC intensities decreased with decreasing temperature. From the relation of log Jph versus 1/T, where Jph is the PC density, two dominant levels were observed, one at high temperature and the other a...

In this study, the photocurrent (PC) spectroscopy of undoped p-type CIS layers has been investigated at temperatures ranging from 10to293K. Three peaks, A, B, and C, corresponded to the intrinsic transition from the valence band states of Γ7(A), Γ6(B), and Γ7(C) to the conduction band state of Γ6, respectively. The crystal field splitting and the spin orbit splitting were found at 0.0059 and 0.2301eV, respectively, and the temperature dependence of the optical band gap could be expressed by using the empirical equation Eg(T)=Eg(0)−(8.57×10−4)T2∕(T+129). But the behavior of the PC was different from that generally observed in other semiconductors: the PC intensities decreased with decreasing temperature. From the relation of logJph vs 1∕T, where Jph is the PC density, the dominant level was observed at the higher temperatures. We suggest that in undoped p-type CIS layers, the trapping center limits the PC signal due to native defects and impurities with decreasing temperature.

A wide-band gap oxide alloy, BeZnO, is proposed and studied in this letter. The BeZnO films were deposited on sapphire substrates by our hybrid beam deposition growth method. The value of the energy band gap of BeZnO can be efficiently engineered to vary from the ZnO band gap (3.4 eV) to that of BeO (10.6 eV). BeZnO can be used for fabricating films and heterostructures of ZnO-based electronic and photonic devices and for other applications. Changes in the measured energy band gap and lattice constant values with Be content are described for BeZnO alloys.

Silicon dioxide films were grown using an oxygen plasma generated by an electron cyclotron resonance (ECR) source at several low temperatures. The plasma oxidation rate was investigated by varying the growth parameters. The oxide thickness parabolically increases with microwave power but decreases with increasing pressure or flow rate. A complementary model of the Deal–Grove oxidation theory is suggested for the plasma oxidation, and kinetic parameters are compared with the other plasma and thermal oxidation cases. The diffusion rate constant in O2 plasma oxidation at room temperature is enhanced up to the level of the diffusion rate in thermal oxidation and the reaction rate constant is much larger than the thermal oxidation case. This may imply that, due to oxygen atoms dissociated by the ECR plasma, plasma oxidation is related to the atomic diffusion through oxide layer and the atomic chemical reaction at the Si–SiO2 interface. The high quality of the ultrathin oxide film was characterized with a break...

The doping characteristics of Mg–Zn codoped GaN films grown by metalorganic chemical vapor deposition are investigated. By means of the concept of Mg–Zn codoping technique, we have grown p-GaN showing a low electrical resistivity (0.72 Ω cm) and a high hole concentration (8.5×1017 cm−3) without structural degradation of the film. It is thought that the codoping of Zn atoms with Mg raises the Mg activation ratio by reducing the hydrogen solubility in p-GaN. In addition, the measured specific contact resistance of Mg–Zn codoped GaN film is 5.0×10−4 Ω cm2, which is one order of magnitude lower than that of Mg doped only GaN film (1.9×10−3 Ω cm2).