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The development of kesterite photovoltaic solar cells has been hindered by large open-circuit voltage (Voc) deficit. Recently, SnZn deep point defect and associative defect cluster have been recognized as the main culprit for the Voc losses. Therefore, manipulating the deep-level donor of SnZn antisite defects is crucial for breaking through the bottleneck of present Cu2ZnSn(S,Se)4 (CZTSSe) photovoltaic technology. In this study, the SnZn deep traps in CZTSSe absorber layer are suppressed by incorporation of Ge. The energy levels and concentration of SnZn defects measured by deep-level transient spectroscopy (DLTS) decrease significantly. In addition, the grain growth of CZTSSe films is also promoted due to Ge implantation, yielding the high quality absorber layer. Consequently, the efficiency of CZTSSe solar cells increases from 9.15% to 11.48%, largely attributed to the 41 mV Voc increment.

The trapping characteristics of point defects in CdZnTe crystals grown by the vertical Bridgman method (VB) and the traveling heater method (THM) were analyzed. The photo-induced current transient spectroscopy (PICTS) was used to determine the traps’ energy, their capture cross-section and concentration. Moreover, the trapping and de-trapping times of point defects were obtained. Furthermore, the photoconductive technology under sub-bandgap illumination were employed to study the influence of the trapping characteristics on mobility-lifetime (μτ) product of CdZnTe crystal. The quantitative results indicated that sub-bandgap illumination can effectively improve carrier mobility-lifetime. The deep levels (TeCd), which occupy the position around the midgap, with high de-trapping time and low trapping time have greater effect on μτ product for the crystals than Cd vacancies. The Te secondary-phase related defects, which can be observed in the VB method grown crystals, have less influence on μτ product than Te antisite.

Electronic traps are the primary factor stifling the performance of quantum-dot (QD) solar cells to nearly half their theoretical potential. Yet, the exact origin of these traps remains largely unknown, making it difficult to address the problem. In the inaugural issue of Matter, Gilmore et al. employ advanced transient spectroscopy to reveal that QD dimerization can be as detrimental as unpassivated surface states in QD films.

Primary defects introduced in boron-doped silicon by an alpha-particle source with a fluence rate of 7 × 106 cm−2 s−1 at cryogenic temperatures were investigated using deep-level transient spectroscopy (DLTS). The data showed that the defects observed between 35 K and 120 K were not detectable when irradiation was carried out at room temperature. The defect levels were observed at 0.10 eV, 0.14 eV and 0.18 eV above the valence band maximum. These levels were attributed to the boron-substitutional vacancy complex, the mono vacancy and a vacancy-related defect respectively.

Time-resolved emission of [Ir(ppy)2dcbpy]Cl (1a, ppy = 2-phenylpyridine, dcbpy = 2,2′-bipyridine-5,5′-dicarboxylic acid) dissolved in DMF revealed a biexponential decay of the excited state. Prior studies on cyclometalated iridium complexes indicated that such dual emission behavior can be attributed to an impurity, compounds that have two LUMO states that are close in energy, or the presence of ion-pairing. To probe each of these effects, a series of homoleptic, Ir(ppy)3 (2), and heteroleptic complexes, [Ir(ppy)2dcbpy]X [X = PF6−(1b), BPh4−(1c)] and [Ir(ppy)2bpy]X [bpy = 2,2′-bipyridine, X = Cl− (3a) PF6−(3b)], were synthesized and photophysically characterized. Among these complexes, only 1a exhibited dual emission with the emission lifetimes of 430 ± 5 ns (80%) and 125 ± 6 ns (20%) in DMF. These lifetimes were further confirmed with the nanosecond transient absorption kinetics, indicating that the dual emission likely did not originate from an impurity. When probing the emission and absorption kinetics of the salts 1b and 1c only one lifetime of 550 ± 10 ns was observed, indicating that the short lifetime of the Cl− salt (1a) comes from a putative ion-paired complex. Density-Functional Theory (DFT) calculations on 1 and 2 fragments in DMF helped uncover the reason behind the ion-pair formation, with carboxyl substituents in 1a causing a loss in electron density on the 3,3′-position of dcbpy. Additionally, the loss in electron density was experimentally validated with 1H NMR, which showed a noticeable downfield shift of the 3,3′-protons in relative to the shifts in 1b and 1c. The data supports that the dual emission observed in 1a is not from two separately emissive states, rather from the dissociated and ion-paired complexes.

InP- and GaAs-based metamorphic In 0.83 Ga 0.17 As photodetectors were grown and investigated. Compared to InP-based photodetector, the dark current of GaAs-based photodetector at room temperature increased 2–3 times but still comparable, whereas at 77 K the dark current increased 2–3 orders. The deep-level transient spectroscopy results reveal that a deep level trap state exists in the GaAs-based photodetector structure. The higher dark current in GaAs-based photodetector at low temperature was mainly ascribed to a deep level trap induced tunneling current. The deep trap centers can also induce non-radiative recombination with smaller thermal active energy in the GaAs-based photodetector structure.

International audience; It is shown that deep level transient spectroscopy can be carried out on Schottky diodes to investigate, in addition to majority carrier traps, minority carrier traps. This is possible thanks to the application of a large reverse bias to the device which allows minority carrier injection by lowering their corresponding effective Schottky barrier height. Indeed, when increasing the reverse bias voltage, the deep level transient spectroscopy signal, initially negative and thus showing only majority carrier traps signature, becomes positive, revealing minority carrier traps involvement. A careful analysis of the recorded spectra leads to the identification of four minority carrier traps which have been so far only evidenced using dedicated technique such as minority carrier transient spectroscopy.

We have investigated p-type semiconductor–ferroelectric TlInS2 by means of Photo-Induced Current Transient Spectroscopy (PICTS) technique in the temperature range 77–350 K for the detection of native deep defect levels in TlInS2. Five native deep defect levels were detected and their energy levels and capture cross sections were evaluated. Focusing on these data, the influence of these defects on the longitudinal and transverse ultrasound waves propagation as well as the effect of electric field on ultrasound waves were studied at different temperatures. The acoustic properties were investigated by the pulse-echo method. The direct contribution of thermally activated charged defects to the acoustic properties of TlInS2 was demonstrated. The key role of charged native deep level defects in elastic properties of TlInS2 was shown.

Studies were performed on two types of chlorine-compensated cadmium telluride crystals with a different density of native dislocations walls. The crystals were investigated by current–voltage measurements, photo-induced current transient spectroscopy and absorption measurements, in the view of investigating the influence of the density of dislocation walls on their charge transport properties and electronic levels scheme. It results that a higher density of dislocation walls increases the dark current in CdTe. To the contrary, the optical absorption properties do not seem to be influenced by the presence of dislocation walls. The PICTS measurements demonstrated that a lower density of dislocation walls provides a higher concentration of compensation-related defects and a lower concentration of the defects responsible for the peaks observed at high temperature, possibly associated to donor-pair complexes.

In this work we present a detailed study of the influence of the GaAs substrate orientation on the electrical properties of heterojunctions based on GaAs and sulfonated polyaniline (SPAN) using Current-Voltage (I-V), Capacitance-Voltage (C-V), Deep-Level Transient Spectroscopy (DLTS) and Laplace DLTS techniques. Three different GaAs substrate orientations have been investigated, namely (1 0 0), (3 1 1)A and (3 1 1)B. The I-V results revealed that the turn-on voltage (Von) of SPAN/(3 1 1)B GaAs heterojunction is higher than that for SPAN/(1 0 0) GaAs and SPAN/(3 1 1)A GaAs heterojunctions. The DLTS results showed that the number of electrically active defects present in devices based on the lower index (1 0 0) plane of GaAs substrate is higher than those of higher index (3 1 1)A and (3 1 1)B GaAs substrates, corroborating with I-V results. In order to investigate the role of interface states, capacitance-frequency measurements were performed in forward bias on all three devices.

The electrical characteristics of Pd Schottky contacts on ZnO films have been investigated by current-voltage (I–V) and capacitance–voltage (C–V) measurements at different temperatures. ZnO films of two thicknesses (400 nm and 1000 nm) were grown by DC-magnetron sputtering on n-Si substrates. The basic structural, optical and electrical properties of these films are also reported. We compared the two Schottky diodes by means of characteristic parameters, such as rectification ratio, ideality factor (η), barrier height (Φb) and series resistance and obtained better results for the 1000 nm-ZnO Schottky diodes. We also discussed the dependence of I‐V characteristics on temperature and the two distinct linear regions observed at low temperatures are attributed to the existence of two different inhomogeneous barrier heights. From I–V plots in a log-log scale we found that the dominant current-transport mechanism at large forward bias is space-charge limited current (SCLC) controlled by the presence of traps within the ZnO bandgap. The existence of such traps (deep states or interface states) is demonstrated by frequency-dependent capacitance and deep-level transient spectroscopy (DLTS) measurements.

In this paper a systematic and detailed study on the photophysical behavior of silicon nanocrystals (alkyl-capped, surface oxidized, oxide-encapsulated) is presented in order to elucidate the influence of local environment and surface species on the luminescence properties. Experiments at different temperatures – ranging from room temperature (RT) to 7 K – confirmed the important influence of the silicon nanocrystal (ncSi) surface on the photoluminescence (PL). Our comparative study of ncSi embedded in different matrices shows a strong increase of the exciton lifetimes at low temperature and the dominant widening of the bandgap for small ncSi after deactivation of traps below 100–150 K. The present findings have significant implications for the use of ncSi in optoelectronic and biomedical applications, since they show that surface oxidation can occur in ligand-capped ncSi which limits the accessible emission wavelength for these applications to the orange/red spectral region when current passivation strategies are used.

The properties of GaAs/AlGaAs solar cells irradiated with 40, 70, 100 and 170 keV protons have been studied. Current–voltage (IV) measurement showed that the worst degradation was found in the cells irradiated by 100 keV protons. The degradation was found defect dependent. Defect profile was obtained by the stopping and range of ions in matter (SRIM) simulation and deep-level transient spectroscopy (DLTS) measurement. In order to obtain the deep-level defect profile in depletion layer by DLTS measurement, the traditional calculation formula of defect concentration has been modified. DLTS measurement showed good agreement with that of the SRIM simulation.

Irradiation of p-GaAs grown by low-pressure metal-organic chemical-vapor deposition (LP-MOCVD) with α-particles from the 241Am source has been performed at room temperature. At least seven radiation-induced deep-level defects at energy positions Ev+0.09 eV, Ev+0.11 eV, Ev+0.16 eV, Ev+0.24 eV, Ev+0.32 eV, Ev+0.42 eV, and Ev+0.77 eV were detected in the lower-half of the band gap, using deep-level transient spectroscopy (DLTS), while no radiation-induced defects were observed in the upper-half band gap (minority carrier injection spectrum). The DLTS signatures of the radiation-induced defects are compared with the previously reported defects introduced in α-irradiated p-GaAs grown by molecular beam epitaxy (MBE). It has been observed that while four of these deep levels are similar to those found in α-irradiated MBE grown p-GaAs, three levels at Ev+0.32 eV, Ev+0.42 eV, and Ev+0.77 eV observed in our MOCVD material were not detected in MBE material. Data on the introduction rates and other characteristics of the radiation-induced defects are presented.

Results of isochronal annealing up to a temperature of 660 K of n-type GaAs grown by low-pressure metal organic chemical vapor deposition (LP-MOCVD) are reported. Deep-level transient spectroscopy (DLTS) reveals EL2 as the only electron-emitting deep-level defect in our as-grown material, whereas three hole-emitting levels at E v +0.09 eV, E v +0.40 eV and E v +0.93 eV are observed in the minority-carrier injection spectra. While yielding interesting results on the behavior of these pre-existing deep-level defects, thermal annealing is found to introduce at least four new defects, three in the upper half of the band gap at E c −0.13 eV, E c −0.16 eV and E c −0.36 eV, and one in the lower half at E v +0.19 eV. Two of these defects, one at E c −0.16 eV and the other at E c −0.36 eV, are identified with previously reported annealed-in deep levels in n-GaAs, while the other two defects cannot be identified with any of the deep levels reported in the literature. Data on the annealing behavior and other characteristics of these annealed-in levels are presented. All the pre-existing inadvertent deep-level defects in the as-grown material were found to be stable up to 600 K, beyond which the minority-carrier emitting levels start to anneal out, but EL2 tends to show a slight increase with annealing temperature.

Polycrystalline CdTe samples were characterized using photo-induced current transient spectroscopy (PICTS). The spectra obtained show that the traps are not discrete ones, or localized bands in the gap like in monocrystalline samples, indeed the PICTS signal presents large peaks. With an improvement of the calculation method presented here, these spectra reveal two types of traps. The first ones are active at low temperature and have energies between 0.3 and 0.5 eV. The second ones are deep level traps located between 0.65 and 0.8 depending on the sample. Focusing on these deep level traps, their influence on the photoconductive response of the material is discussed.

The photophysical properties of mononuclear Pt II chromophores of the general structural formulae: Pt(LL)(C CR) 2 and [Pt(LLL)(C CR)] + (LL = substituted or unsubstituted 2,2′-bipyridine; LLL = substituted or unsubstituted 2,2′:6′,2″-terpyridine; R = aryl or alkyl) are described. Topics related to their preparation, spectroscopy, photochemistry, and photophysics are reviewed.

Self-organised InAs/GaAs quantum dots (QDs) were formed by molecular beam epitaxy using the Stranski–Krastanov growth mode. Deep-level transient spectroscopy as well as secondary ion mass spectrometry have been used to characterise structures containing the QDs. DLTS depth profiling procedures indicate that deep level-related defects are localised in GaAs in the vicinity of the QD plane. For the first time, we report the presence of a deep level-related trap with an extremely high thermal activation energy of E c − 1.03 eV. An electron trap at E c − 0.78 eV can be identified as the well-known level related to the EL2 family. We conclude that a third trap revealed at E c −0.57 eV is the familiar PL killer related to the intrinsic point defect-oxygen complex. The latter is confirmed by results of the SIMS study, which indicates that the amount of oxygen accumulated at the InAs/GaAs heterointerface is increased. This paper demonstrates that the EL2 and oxygen-related deep-level centers occur by the presence of InAs/GaAs QDs. We present the hypothesis that deep states could be a factor limiting the efficiency of QD-based devices.

Inductively coupled plasma-(ICP-)induced defects in n-type GaN have been studied from current–voltage ( I – V ) characteristics and deep-level transient spectroscopy (DLTS) for Schottky diodes fabricated on etched surfaces. The samples after ICP etching show the ohmic I – V characteristics. Schottky characteristics are obtained after annealing at 600 and 800 °C in N 2 , but are not restored to that of the control samples. DLTS shows that the effect of ICP etching is small on the region beyond 80 nm from the surface. These results suggest that there remain ICP-induced damage in the near-surface region after thermal annealing.

Deep-level transient spectroscopy (DLTS) and capacitance versus voltage measurements were used to study an influence of deep-level defects on electrical parameters of Yb–Al co-doped GaAs:Sn grown by liquid-phase epitaxy. DLTS spectra revealed the presence of several hole traps. Some of them were attributed to transition metals and native defects, respectively, which were commonly observed in as-grown material. It was found that increasing Yb caused a decrease in free carrier concentration. However, it was accompanied by an increase in the hole trap concentrations. On the other hand, adding Al resulted in a strong decrease in both the free carriers and the hole traps. The fact that deep levels may behave in this manner after adding Yb and Al into the Ga melt is an important factor to consider when interpreting changes in electrical parameters of the material.

High-resolution photoinduced transient spectroscopy (HRPITS) has been used to investigate defect centres in n-type epitaxial silicon after 24 GeV/c proton irradiation with fluences of 3×1014 and 9×1014 cm−2 followed by a long-term annealing at 80 oC. The measurements revealed nine traps with activation energies ranging from 5 to 460 meV. In the material irradiated with the lower fluence the concentration of V2O−/0 complexes is found to be approximately 4 times lower than that of divacancies V2−/0. After the irradiation with the higher fluence the material defect structure is different and the concentration of V2O−/0 complexes is around 6 times higher compared to that of divacancies V2−/0.

The Franklin Institute, Philadelphia, Pennsylvania, awarded the 2004 Benjamin Franklin Medal in Chemistry to Harry B. Gray for his pioneering contributions in the field of electron transfer in metalloproteins. In a series of elegant and challenging experiments beginning in the late 70s, Gray and his coworkers have shown that the transfer of electrons in metalloproteins can proceed over long distances (~ 20 A) and at fast rates. These experiments have involved the regiospecific functionalization of structurally characterized electron transfer proteins with ruthenium complexes, coupled with laser excitation and transient spectroscopy. Probing the effects of thermodynamic driving force, temperature, donor–acceptor distance and electronic coupling, Gray has shaped our detailed current understanding of the principles governing biological electron flow. The mechanism of electron transfer has been identified as electron tunneling mediated by the molecules separating donor and acceptor. Tunneling timetables have been established for various intervening media. Important biological processes like respiration and photosynthesis depend on facile electron transfer, and Gray's contribution serves as the fundamental basis for understanding these and many related reactions.

In this paper, static measurements and defect analysis performed on InAlAs/InGaAs/InP HFETs are presented. I d – V ds – T , I d – V gs – T and I g – V gs – T characteristics show anomalies (leakage current, degradation in saturation current, kink effect, distortions on I d – V d characteristics in saturation region after high voltage application, …). Deep defects analysis performed by means of capacitance transient spectroscopy (C-DLTS) and frequency dispersion of the output conductance ( G ds ( f )) prove the presence of deep defects with activation energies ranging from 0.12 to 0.75 eV. The presence of generation–recombination centers, acting like traps, is confirmed by I g – V gs . The localization and the identification of these defects are presented. Finally, the correlation between the anomalies observed on output characteristics and defects is discussed.

Capacitance–voltage measurements at 77 and 300 K have shown that 11 keV hydrogen ion implantation of n-Si/SiO 2 structure generates defects in the SiO 2 film and at the Si/SiO 2 interface. Deep-Level Transient Spectroscopy spectra reveal the creation of deep levels in the Si substrate. In the accumulation mode tunnelling type conduction through the 120 nm thick SiO 2 film is observed.

Deep-level transient spectroscopy (DLTS) on HVPE grown n-GaN revealed three dominant traps below the conduction band, commonly associated with HVPE-grown material. In this study, it was found that the concentration of the EC−0.61 eV level is dependent on the biasing conditions: zero bias annealing at 370 K decreases the concentration of the 0.61 eV level to a non-zero value, while reverse bias annealing increases the concentration within the region probed. The change in the defect concentration becomes lower for thicker GaN layers with a lower density of threading dislocations. We tentatively ascribe this behaviour to the neutralisation of the 0.61 eV level by a mobile defect species, which is associated with dislocations present in the material.

The effect of implantation angle on the profile of the vacancy-phosphorus and divacancy centres (VP/V 2 − ) in n-type 0.7–1.1 Ω cm Cz-grown (1 0 0) Si has been examined using depth profiling with deep-level transient spectroscopy. Samples were mounted with 10° twists from the [1 1 0] direction and various tilts from the [1 0 0] direction then implanted with 600 keV P to a dose of 5×10 8 cm −2 . The peak depth of the VP/V 2 − profile exhibits a systematic variation with the implantation angle: narrowing and increasing in peak concentration as the implantation angle is progressively varied from the aligned direction. The defect profiles are approximately 0.3 μm deeper than the peak in the vacancy profile predicted using the binary collision code Crystal-TRIM. Surface-enhanced annihilation of migrating defects has been considered as the cause of this.

The electrical and optical properties of defects introduced into silicon either by plastic deformation at 630°C or by MeV self-implantation and subsequent annealing at 630°C are compared. It is shown, based on the new experimental results and literature data that most of the deep-level transient spectroscopy (DLTS) lines revealed in the deformed crystals coincide with the DLTS signatures of small interstitial clusters in the dislocation-free implanted/annealed samples. In opposite, the photoluminescence (PL) D1–D4 dislocation bands are observed only in the dislocated crystals.

We investigated the influence of different Cu and Na contents on the electrical properties of Cu(In,Ga)(S,Se) 2 solar cells. The devices were characterized applying admittance spectroscopy and deep-level transient spectroscopy (DLTS). We observed four kinds of deep defect states in differing concentrations in the stoichiometry-varied samples: two acceptor-like deep-level states, one donor-like trap, and a midgap center. In order to characterize the properties of these defect states, we recorded the DLTS capacitance transients of a Na poor sample with different pulse widths (ranging from 100 μs to 1 s duration) at selected fixed temperatures. We discuss the properties of the defect states.

Photo-induced current transient spectroscopy is an efficient technique for the detection and identification of traps in semiconductors. This technique has been used to determine the traps in various semiconductors. CdTe is one of the leading candidates for the development of thin film solar cells; hence, the detection of trap levels in CdTe is of interest for the photovoltaic researchers. In this review special emphasis is given to the photo-induced current transient spectroscopy (PICTS) technique applied in the case of CdTe. The PICTS technique, theory as well as a collection of the majority of the traps in CdTe reported in the literature are presented.

Interface properties of dilute slightly lattice mismatched GaAsN/GaAs (0.35 at.% N) and closely lattice matched InGaAsN (1 at.% In, 0.35 at.% N) heterojunctions (HJs) were studied by means of capacitance–voltage profiling, deep levels transient spectroscopy (DLTS) and current–voltage measurements. It is found that the lattice matched HJs show no electrical breakdown when the space charge region crosses the interface. The carrier concentration profiles in such HJ show, as expected, the accumulation region on the low-bandgap side and the depletion region on the high-bandgap side of the HJ. This is not the case for the GaAsN/GaAs (GaAsN layer on top) and the GaAs/GaAsN (GaAs layer on top) HJ. The density of deep traps in GaAsN, InGaAsN films and in GaAs films grown on GaAsN underlayers was very much higher than in epitaxial GaAs films. The dominant deep centers were the EL6 and the EL3 electron traps. The interface regions of the GaAs/GaAsN and the InGaAsN/GaAs HJs were shown to be enriched by EL3 traps, while for the GaAsN/GaAs HJ those regions were enriched by EL6 traps which was associated with the former films being Ga-rich and thus facilitating incorporation of oxygen on As sites.

This work deals with the performances of two electrical techniques to characterize deep levels in HEMTs. Capacitance Deep Level Transient Spectroscopy (DLTS) is a well-known method and its efficiency is now proved, whereas Drain Current Transient Spectroscopy (DCTS) provides information about the location of traps in the structure. Experimental results establish the complementarity of these two techniques.

High-temperature isothermal capacitance transient spectroscopy (H-ICTS) measurements were conducted to characterize near mid-gap defects, which are the origin of the memory effect in Ni/p-GaN Schottky contacts. A large single peak was detected only under the forward bias conditions. This indicates that the defects were located in the vicinity of the interface. The change of the peak height and position of the ICTS curves under various bias conditions were qualitatively interpreted by the distribution of the defects and the current flow effect.

High-resolution photoinduced transient spectroscopy (HRPITS) has been applied to study the electronic properties of grown-in point defects in semi-insulating (SI) GaAs bulk crystals grown by liquid encapsulated Czochralski (LEC) and vertical gradient freeze (VGF) methods. The novel method, which represents the significant improvement of the earlier PITS technique, relies on the extraction of trap parameters from the digitally recorded photocurrent transients by means of the correlation procedure. The influence of the crystallisation conditions on the defect structure of high resistivity GaAs is compared. In the VGF material the concentrations of traps P6 (0.05 eV), P7 (0.08 eV), P12 (0.18 eV), EL14 (0.22 eV) and EL3 (0.58 eV), tentatively identified as V As −/0 , Ga As 0/− , B As −/−− , V Ga –V As and O i –V As , respectively, are found to be much lower than in the LEC material.

Further evidence was found that the 0.8 eV luminescence band in GaAs is correlated to the EL6 defect as identified by photo induced current transient spectroscopy (PICTS). From luminescence topography arguments are put forward that the EL6 defect should not be the dominant recombination centre in GaAs. By the application of microwave detected PICTS it could be shown that the EL6 is definitely not a relevant recombination centre. Recombination takes place most probably via different, partially not jet identified centres.

Non-destructive and spatially resolved (35 μm) characterisation methods for high resistivity GaAs and epitaxial substrates are presented. Microwave detected photo induced current transient spectroscopy (PICTS) is a further development of the already existing method Microwave detected photoconductivity (MDP). Using various GaAs samples of different preparations, the possibilities of these new tools are demonstrated along with the first results for technologically relevant extrinsic and intrinsic defects.

Conducting and semi-insulating crystals of GaAs grown by vertical Bridgeman (VB) and liquid encapsulated Czochralski (LEC) methods were studied by means of deep levels transient spectroscopy, photoinduced current transient spectroscopy, panchromatic microcathodoluminescence, optical absorption and electrical measurements. The most prominent traps observed in both types of crystals were the EL8, EL6, EL5, EL3 and EL2 electron traps. The results suggest that VB crystals are similar to LEC GaAs crystals grown from slightly Ga rich melts. The electrical properties and uniformity of VB crystals were greatly improved by the standard 950 °C annealing procedure.

Experiments on proton irradiation with energy of 150 KeV, 8 MeV and 1 GeV were made. Capacitance–voltage characteristics measured at 650 K showed that 8 MeV and 1 GeV proton irradiation of 6H-SiC leads to an increase of uncompensated donor concentration. However, donor concentration in 6H-SiC remains unaffected after 150 keV proton irradiation. Deep centers were investigated by deep levels transient spectroscopy (DLTS). Results of C–V measurements are interpreted using DLTS data. The results obtained show the possibility of uzing proton irradiation for producing local high-resistance regions in SiC devices not intended for high-temperature applications.

High resolution Laplace minority carrier transient spectroscopy (LMCTS) has been used to study defects in gas source molecular beam epitaxy grown Si/Si0.855Ge0.145 strained quantum wells. In LMCTS, the minority carrier emission transient is analysed and detailed emission properties of minority carrier traps which have similar energy can be characterised. The technique was evaluated by comparing LMCTS of a Au : H hole trap, G3, in n-type silicon with Laplace deep level transient spectroscopy of the same trap in p-type silicon. Both techniques confirm that this level consists of two states, as previously suggested in the literature. MCTS was then applied to the n-type Si/SiGe quantum well sample, and five-hole traps were observed. A level at 95 K in the MCTS spectrum was identified as a possible candidate for hole emission from the quantum wells. LMCTS showed that the emission rate of this hole trap exhibited only a slight temperature dependence compared to that exhibited by hole states associated with isolated point defects. This is attributed to holes tunnelling out of the quantum well assisted by the electric field present in the experiment.

The pseudomorphic AlGaAs/InGaAs/GaAs MODFET, intended for future applications in cryoelectronics, has been investigated. In the temperature range of 10–350 K no collapse nor Kink effect have been detected. However, a threshold shift has been observed which is thought to be associated with electrically active defects in the heterostructure. The related deep levels are directly characterized by two electrical techniques: capacitance deep level transient spectroscopy and drain current transient spectroscopy. Experimental results establish the complementarity of both techniques.

Capacitance–voltage measurements and deep-level transient spectroscopy have shown that RF hydrogen plasma treatment of thin (13 nm) SiO 2 /p-Si structures at 20, 100 and 300°C generates defects in the oxide, at the SiO 2 /Si interface and in the near-surface region of Si substrate. The density of these defects depends on the substrate temperature during plasma exposure. The concentration of plasma-induced defects is the highest at 20°C. With increasing treatment temperature the densities of positive oxide charges, donor-like interface traps and deep levels in the Si bulk decrease.

Using deep-level transient spectroscopy (DLTS), we have found that 1 MeV proton bombardment introduces the ER3, nitrogen vacancy related defect, at a rate of 290±50 cm −1 . Further, using capacitance–voltage (C–V) measurements, we have found that 1 MeV protons remove free carriers at a rate of 3880±380 cm −1 . However, when bombarding GaN with 0.5 keV protons, we did not observe the ER3 defect. We propose that 0.5 keV protons indeed introduce the ER3 defect, but that it is passivated by hydrogen.

Optical transient current spectroscopy (OTCS) has been used to investigate defects in the low-temperature-grown GaAs after postgrowth rapid thermal annealing (RTA). Two samples A and B were grown at 220 degreesC and 360 degreesC on (001) GaAs substrates, respectively. After growth, samples were subjected to 30s RTA in the range of 500-800 degreesC. Before annealing, X-ray diffraction measurements show that the concentrations of the excess arsenic for samples A and B are 2.5 x 10(19) and 1 x 10(19) cm(-3), respectively. It is found that there are strong negative decay signals in the optical transient current (OTC) for the annealed sample A. Due to the influence of OTC strong negative decay signals, it is impossible to identify deep levels clearly from OTCS. For a comparison, three deep levels can be identified for sample B before annealing. They are two shallower deep levels and the so-called As-Ga antisite defect. At the annealing temperature of 600 degreesC, there are still three deep levels. However, their structures are different from those in the as-grown sample. OTC strong negative decay signals are also observed for the annealed sample B. It is argued that OTC negative decay signals are related to arsenic clusters. (C) 2000 Elsevier Science B.V. All rights reserved.

GaNAs crystals grown by the metalorganic vapor-phase epitaxy (MOVPE) method are characterized by plane-view electron beam induced current (EBIC) and deep-level transient spectroscopy (DLTS). Localized deep-level traps with a diameter of 3–5 μm are clearly observed from EBIC analysis. The DLTS analysis shows that the dominant deep-level traps have energy levels of Ev+0.58 eV and Ec−0.72 eV. Such deep level traps are eliminated by annealing at 700°C. From our analysis, the change in the spatial distribution of deep-level traps due to annealing correlates strongly with the change in the PL intensity, indicating that observed deep-level traps are one of the major factors which degrade the optical properties of the GaNAs crystals. In addition to these localized traps, the inhomogeneity of minority diffusion length is also detected by EBIC.

Al-related DX-like centers were observed in n-type Al-doped ZnS1-xTex epilayers grown by molecular-beam epitaxy on GaAs substrates. The capacitance-voltage measurement, deep-level transient spectroscopy, and photoconductivity spectroscopy revealed that the behaviors of Al donors in ZnS1-xTex were similar to the so-called DX centers in AlxGa1-xAs. The optical ionization energies (E-i) and emission barriers (E-e) for the observed two Al-related DX-like centers were determined as E-i similar to 1.0 and 2.0cV and E-e similar to 0.21 and 0.39 eV, respectively. It was also shown that the formation of Al-related DX-like centers resulted in a significantly large lattice relaxation in ZnS1-xTex. (C) 2000 Elsevier Science B.V. All rights reserved.

Simulation of a deep-level transient spectroscopy (DLTS) spectrum was carried out with numerical calculation of the Poisson equation for a sample whose carrier concentration is inhomogeneous in depth. The calculated DLTS spectrum shows two peaks, although one electron trap was assumed to exist in the sample. One is a spurious peak which shows anomalous trap parameter values. This spurious peak is caused when the depletion region edge moves within the region where the carrier concentration is inhomogeneous.

Deep-level transient spectroscopy was used to investigate the effect of alpha particle irradiation on the electrical properties of n-type Ge. The samples were irradiated with alpha particles at room temperature using an americium-241 (Am-241) radionuclide source. The main defects introduced were found to be electron traps with energy levels at EC 0.38, EC 0.21, EC 0.20, EC 0.15, and EC 0.10 eV, respectively. The main defects in alpha particle irradiation are similar to those introduced by MeV electron irradiation, where the main defect is the E-center. A quadratic increase in concentration as a function of dose is observed. & 2009 Published by Elsevier B.V.

Deep-level transient spectroscopy (DLTS) measurements have been carried out to investigate the deep levels existing in Ti-doped GaAs epilayer grown on GaAs substrates by liquid phase epitaxy. While one hole-trap was observed for the undoped GaAs epilayer, two new traps appeared for the Ti-doped GaAs epilayers. The trap activation energies and the capture cross-sections for the two traps appearing in the Ti-doped GaAs epilayers are 0.2 eV and 3.5×10 −17 cm 2 for the Ti 2+ /Ti 3+ peak, and 0.93 eV and 3.11×10 −15 cm 2 for the Ti 3+ /Ti 4+ peak. These results indicate that the Ti-doped GaAs epilayer forms new defect levels and that the levels restrict the activation of transformed impurities. Furthermore, the present results can help improve the understanding of the applications of Ti-doped GaAs epilayers in electronic devices.

We review our recent studies on the reactions of hydrogen with transition-metals (Pd, Pt, Ag, and Au) in crystalline Si. Hydrogen was incorporated into the samples by wet-chemical etching. Deep-level transient spectroscopy (DLTS) on Schottky diodes reveals several transition metal‐hydrogen complexes in n- and p-type samples. From DLTS profiling, we are able to estimate the number i of hydrogen atoms in the TM‐Hi complexes. All complexes with i 1, 2 are electrically active. Striking similarities are found for isoelectronic complexes, e.g. Pt‐H2 and Au‐H1. Transition metal complexes with more than three hydrogen atoms are likely to be electrically passive. All hydrogen related complexes disappear after heat treatments above 600 K for several hours. © 1999 Elsevier Science S.A. All rights reserved.

The effect of wet chemical etching and subsequent annealing on the electrical activity of the dislocation-related centers in n-type Si is investigated by the deep-level transient spectroscopy. It is observed that hydrogen penetrates into the samples already during room temperature etching but passivates the dislocation centers only after 300°C annealing. The different dislocation centers exhibit different efficiency of hydrogen passivation. Possible reasons for the observed peculiarities of the dislocation passivation are discussed.

Photo-induced-current transient spectroscopy and capacitance–voltage measurements on nominally undoped p-CdTe single crystals grown by a Bridgman method have been carried out to investigate the hydrogenation and the annealing effects on the deep levels and on acceptor neutralization. The five hole-traps of the as-grown p-CdTe and their activation energies were E v +0.21 (H 1 ), E v +0.39 (H 2 ), E v +0.43 (H 3 ), E v +0.65 eV (H 4 ), and E v +0.75 (H 5 ). After the p-CdTe was hydrogenated and annealed, H 4 and H 5 related to Cd vacancies disappeared, and the intensity of H 3 related to the native defects decreased by a factor of 2. H 4 and H 5 traps were passivated by the hydrogen atoms. The H 3 defect level is considered to be due to complexes of Cd vacancies and impurities, and the H 2 signal is associated with complexes of shallow impurities. The results of the PICTS measurements showed that hydrogen atoms easily neutralize the Cd vacancies and that the hydrogen atoms are easily separated from the impurities by the thermal energy. These results indicate that the electrical properties of the undoped p-CdTe single crystals are improved by hydrogenation and annealing and that hydrogenated and annealed CdTe crystals hold promise as useful substrates for the growth of Hg x Cd 1 x Te.