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Electron traps generated during the reactive ion etching (RIE) process in n-type 4H-SiC are investigated using the deep-level transient spectroscopy technique and isothermal capacitance transient spectroscopy (ICTS) technique. Two electron traps of the Z1/2 center ( EC−0.64eV) and the EH3 center ( EC−0.74eV) are detected in the RIE-etched sample by ICTS measurement at 300 K. A method is proposed to determine the depth profiles of the electron traps that are localized near the etched surface, whereby a depth profile is extracted from the dependence of averaged trap density on the depletion layer width. An exponential distribution is assumed as the depth profile of the electron traps generated during the RIE process. The extracted depth profile was confirmed to be consistent with that determined by the double-correlation method. An appropriate function for the depth profile of carrier traps is assumed and the dependence of the averaged trap density on the depletion layer width is analyzed, which enables the extraction of a depth profile that has both higher depth resolution and higher resolution in the carrier trap density with the proposed method than that with the double-correlation method.

This theoretical–experimental study focuses on the formation of the substitutional-tri-interstitial cluster Cus1Cui3, which has been proposed as the photoluminescence defect CuPL. The configurations and electronic properties of the intermediate defects Cus1Cui1 and Cus1Cui2 are calculated, and their electrically active levels are obtained from conventional and Laplace deep-level transient spectroscopy. The vacancy formation energy near copper-related defects is calculated and found to be much smaller than in the perfect crystal. Then, we show how Cus1Cui3 could become the seed of agglomerates of Cus1Cui3 “units.” The discussion focuses mostly on unanswered questions about the discrepancies between the calculated and measured properties of CuPL and Cus1Cui3.This theoretical–experimental study focuses on the formation of the substitutional-tri-interstitial cluster Cus1Cui3, which has been proposed as the photoluminescence defect CuPL. The configurations and electronic properties of the intermediate defects Cus1Cui1 and Cus1Cui2 are calculated, and their electrically active levels are obtained from conventional and Laplace deep-level transient spectroscopy. The vacancy formation energy near copper-related defects is calculated and found to be much smaller than in the perfect crystal. Then, we show how Cus1Cui3 could become the seed of agglomerates of Cus1Cui3 “units.” The discussion focuses mostly on unanswered questions about the discrepancies between the calculated and measured properties of CuPL and Cus1Cui3.

While carbon doping is known to increase the resistivity of GaN, highly resistive layers for device isolation can also be obtained by ion implantation. In this study, we report on the electrical characterization of C-implanted n-type homoepitaxial GaN. Our investigation, carried out by capacitance-voltage measurements and deep level/minority carrier transient spectroscopy, revealed the presence of nine majority carrier traps in the 0.2–1.3 eV energy range, below the conduction band edge, and of four minority carrier traps, in the 0.1–1.4 eV energy range, above the valence band edge. The net-donor compensation mechanism and the behavior of defect centers are studied as a function of the annealing temperature in the 100–1000 °C range. While the former is explained in terms of dynamic annealing, the latter is discussed in the light of the present experimental results and those found in the literature.

A border trap (BT) evaluation method was established for SiO2/GeO2/Ge gate stacks by using deep-level transient spectroscopy with a lock-in integrator. Ge metal-oxide-semiconductor capacitors (MOSCAPs) with SiO2/GeO2/Ge gate stacks were fabricated by using different methods. The interface trap (IT) and BT signals were successfully separated based on their different dependences on the intensity of injection pulses. By using p-type MOSCAPs, BTs at the position of 0.4 nm from the GeO2/Ge interface were measured. The energy of these BTs was centralized at the position near to the valence band edge of Ge, and their density (Nbt) was in the range of 1017–1018 cm−3. By using n-type MOSCAPs, BTs at the position range of 2.8–3.4 nm from the GeO2/Ge interface were measured, of which Nbt varied little in the depth direction. The energy of these BTs was distributed in a relatively wide range near to the conduction band edge of Ge, and their Nbt was approximately one order of magnitude higher than those measured by p-MOSCAPs. This high Nbt value might originate from the states of the valence alternation pair with energy close to 1 eV above the conduction band edge of Ge. We also found that Al post metallization annealing can passivate both ITs and BTs near to the valence band edge of Ge but not those near to the conduction band edge.

Detector-grade undoped chemical vapor deposited (CVD) diamond samples have been studied with thermally stimulated currents (TSC) and photoinduced current transient spectroscopy (PICTS) analyses in the temperature range 300–650 K. Two previously unknown defects have been identified, characterized by activation energies E1=1.14 eV and E2=1.23 eV, cross sections of about σ≈10−13 cm2 and concentrations of Nt≈1016 cm−3. They have been clearly observed by PICTS and isolated in TSC measurements by use of a fractional annealing cycle in the temperature range 300–400 K. Due to their trap parameters, in particular the high cross section, the levels corresponding to E1 and E2 are characterized by capture times of the order of 10–100 ps. A dominant TSC peak observed at ≈500 K has been also investigated and has been resolved into four components with activation energies of the order of 1 eV and cross sections in the range 10−19–10−17 cm2. Three of these levels exhibit a fast capture rate (0.1–10 ns) in spite of their ...

Dislocated Si, SiGe, SiC, and SiGeC n-type heterostructures, grown by molecular beam epitaxy, were characterized by capacitance–voltage profiling and deep-level transient spectroscopy. Exclusively dislocation-related defects were found in the different layers, which correspond to the well-known defects found in plastically deformed silicon.

A theory of the transient spectroscopy of quantum well (QW) structures under a large applied bias is presented. An analytical model of the initial part of the transient current is proposed. The time constant of the transient current depends not only on the emission rate from the QWs, as is usually assumed, but also on the subsequent carrier transport across QWs. Numerical simulation was used to confirm the validity of the proposed model, and to study the transient current on a larger time scale. It is shown that the transient current is influenced by the nonuniform distribution of the electric field and related effects, which results in a step-like behavior of the current. A procedure of extraction of the QW emission time from the transient spectroscopy experiments is suggested., 5 pages, 4 figures, to be published in J. Appl. Phys

Photoinduced current transient spectroscopy (PICTS) is used to study deep minority carrier traps in n-type ultrapure germanium (shallow concentration of the order 109 cm−3). In this technique, which is a variant of deep level transient spectroscopy (DLTS), a neutral structure with two ohmic contacts applied on two opposite faces of the sample is illuminated through one of the contacts with intrinsic, strongly absorbed light. The current transients which follow after interrupting the photoexcitation are analyzed using classical double lock-in DLTS resulting in the detection of centers in the minority half of the band gap (provided the back ohmic contact is negative). After correcting the PICTS spectra for the temperature dependence of the mobility, six peaks superimposed on a broad background are clearly resolved. The peaks are the same as the ones found earlier in high-purity n-type germanium (shallow concentration of the order 1010 cm−3) using optical DLTS. These peaks are mainly Cu related. A formula to...

The fluence-dependent properties and the annealing behavior of electron-irradiation-induced deep levels in n-type 6H–SiC have been studied using deep-level transient spectroscopy (DLTS). Sample annealing reveals that the dominant DLTS signal at EC−0.36 eV (labeled as E1 by others) consists of two overlapping deep levels (labeled as ED3L and ED3H). The breakup temperature of the defect ED3L is about 700 °C. The ED3H center together with another deep level located at EC−0.44 eV (so-called E2) can withstand high-temperature annealing up to 1600 °C. It is argued that the involvement of the defect ED3L is the reason that various concentration ratios of E1/E2 were observed in the previous work. The revised value of the capture cross section of the deep-level ED3H has been measured after removing ED3L by annealing. A deep level found at EC−0.50 eV is identified as a vacancy–impurity complex since it was found to have a lower saturated concentration and weak thermal stability. Two other deep levels, EC−0.27 eV an...

We employed capacitance-voltage (C–V) measurements to determine the free-carrier concentration changes in n-GaAs after processing it in a He plasma, and deep-level transient spectroscopy (DLTS) to study the electrical properties of the plasma-induced defects. C–V measurements indicated that He-plasma processing resulted in a strong carrier reduction up to 1 μm below the GaAs surface. DLTS showed that He-ion processing introduced several prominent defects, including the frequently studied radiation-induced defects E1 and E2, associated with VAs. Current-voltage measurements demonstrated that the He-plasma processing inhibits the fabrication of high barrier Schottky diodes on n-GaAs.

Properties of interface states at Ta2O5/n-Si interfaces are studied by capacitance–voltage and deep-level transient spectroscopy (DLTS) measurements. The results show that the “slow” states at Ta2O5/n-Si interfaces are not significantly affected by annealing, and their density is about 1.4–1.9×1011 cm−2. The energy distribution of the “fast” interfacial states in the band gap of silicon is obtained, and some high concentration interfacial states are found. DLTS spectra reveal that the interfacial defects at Ta2O5/n-Si interfaces are all donor type. The high concentration interfacial defects are located at about 0.40 eV below the conduction-band minimum of silicon. Their density decreases with increasing annealing temperature. The origin is suggested to be related to the diffusion of tantalum into the Si substrate.

The deep levels present in semiconducting CdTe and semi-insulating CdTe:Cl and Cd0.8Zn0.2Te have been investigated by means of cathodoluminescence, deep level transient spectroscopy (DLTS), photo-induced current transient spectroscopy, and photo-DLTS. The latter two methods, which can be applied to semi-insulating materials, allow to characterize the deep traps located up to midgap and can determine whether they are hole or electron traps. We have identified 12 different traps, some common to all the investigated samples, some peculiar to one of them. A comparison of the results obtained from the various materials is given and the status of defect models is reviewed.

The capture and emission dynamics of deep levels in GaAs/Ga1-xAlxAs multiple quantum well structures are investigated by using the photoinduced transient spectroscopy technique, In nominally undoped samples three trapping levels with activation energies in the range between 0.4 and 0.8 eV are observed. These are compared with the observations based on other conventional techniques. Large capture cross sections associated with the trapping centers implies that the presence of these can be detrimental for the high speed operation of optoelectronic devices based on GaAs/Ga1-xAlxAs quantum well structures. (C) 1997 American Institute of Physics.

Defects in Si-doped InxAl1−xAs (0

Spectra of hole and electron traps of CuInSe2/CdS/ZnO photovoltaic devices have been investigated using deep‐level transient spectroscopy. A decrease of the concentration of shallow electron traps and an increase of the hole trap concentration after an injection of electrons has been observed. The effect is metastable below 200 K. A proposed explanation is based on the idea that both levels belong to the same defect in a different charge state. A resemblance of the phenomena related to that defect and to ‘‘dangling bond’’‐type centers in amorphous semiconductors has been indicated. Some consequences of defect conversion for current transport and performance of photovoltaic devices have been discussed.

The presence and evolution of traps in undoped semi‐insulating (SI) InP obtained by high temperature annealing (900 °C for 90 h) in poor or rich phosphorus atmosphere has been studied by means of photoinduced current transient spectroscopy. Six traps named A1 to A6 having activation energies ranging from 0.2 to 0.6 eV have been detected in three samples submitted to the same annealing process. The samples differ in the Fe concentration of the starting material and the applied phosphorus pressure in the annealing process. A comparison of the corresponding photoinduced current transient spectroscopy spectra shows that among the observed traps, the 0.2 eV one can be related to a phosphorus deficiency, and the 0.3 eV and 0.4 eV traps could be due to an excess of phosphorus during annealing. Moreover, the trap corresponding to iron (0.6 eV) has been observed in all the studied samples.

In this paper, the properties of point defects in Cd1−xZnxTe1−ySey (CZTS) radiation detectors are characterized using deep-level transient spectroscopy and compared between materials grown using two different methods, the Bridgman method and the traveling heater method. The nature of the traps was analyzed in terms of their capture cross-sections and trap concentrations, as well as their effects on the measured charge-carrier trapping and de-trapping times, and then compared for the two growth techniques. The results revealed that Se addition to CdZnTe can reduce the VCd− concentration. In Travelling Heater Method (THM) and Bridgman Method (BM) grown CZTS detectors, besides a few similarities in the shallow and medium energy traps, there were major differences in the deep traps. It was observed that the excess-Te and lower growth-temperature conditions in THM-grown CZTS led to a complete compensation of VCd− and two additional traps (attributed to Tei− and TeCd++ appearing at around Ev + 0.26 eV and Ec − ...

Close-spaced vapor transport (CSVT) provides a plausible path to lower the costs of GaAs deposition as it uses only solid precursors and provides precursor utilization in principle approaching 100%. However, the use of H2O as a transport agent causes O to be incorporated in CSVT films, and O has been associated with a number of electrically active defect centers in GaAs, which decrease minority carrier lifetimes. Using deep-level transient spectroscopy, we study the effect of H2O concentration and substrate temperature on electron trap concentrations in n-type GaAs. We find that the most-prominent O-related center (ELO) typically has a much higher concentration than the center usually associated with As antisites (EL2), but that overall defect concentrations can be as low as those in films deposited by common vapor phase techniques. The trends with increasing H2O concentration suggest that ELO is most likely a defect complex with two As antisites. We also consider the optimal conditions for achieving high...

Contactless capacitance transient techniques have been applied to local mapping of interface traps of a semiconductor wafer. In contactless capacitance transient techniques, a Metal-Air gap-Oxide-Semiconductor (MAOS) structure is used instead of a conventional Metal-Oxide-Semiconductor (MOS) structure. The local mapping of interface traps was obtained by using a contactless Isothermal Capacitance Transient Spectroscopy (ICTS), which is one of the contactless capacitance transient techniques. The validity of the contactless ICTS was demonstrated by characterizing a partially Au-doped Si wafer. The results revealed that local mapping of interface traps using contactless capacitance transient techniques is effective in wafer inspection and is a promising technique for the development of MOS devices and solar cells with high reliability and high performance.

Deep‐level transient spectroscopy has been used to study the properties of electron and hole traps present in n‐type GaAs1−xPx alloys and their evolution versus the alloy composition. An electron trap labeled E0 is observed for all values of the alloy composition x, while a second electron trap E1 appears only for 1≳x≥0.81. As for hole traps one (H2) appears for 1≳x≥0.75, while two others, H0 and H1, are detected for x≥0.81 and for 1≳x≥0.81, respectively. Their ionization energies have been determined and the barriers, associated with electron capture, have been measured in order to determine the energetic position of the two electron traps relative to the conduction band.

Experiments of deep‐level transient spectroscopy and transmission electron microscopy (TEM) observations have been carried out on heat‐treated Σ=25 silicon bicrystals precontaminated with nickel before being heat treated at various temperatures Ta. For the lowest Ta value (600 °C), the electronic interface states were found to be shared between two overlapping narrow continua around Ec−0.63 eV and Ec−0.52 eV. Upon increasing Ta, these states shift toward shallow positions and exhibit a marked tendency to shrink and to turn into a unique trap level. While the annealing at 900 °C has led to a single state at Ec−0.50 eV, this later moved to Ec−0.48 eV for 1000 °C and then to Ec−0.44 eV for 1100 °C, with an accompanying consistent lowering in the barrier height (BH). TEM observations demonstrated the formation of pure type‐B NiSi2 platelets for 800 °C, but indicated an increasingly important growth of type A for increasingly higher Ta values. While the existence of a unique trap level at high Ta could be explained, like previous findings, by some ‘‘uniform’’ coverage of the boundary by the precipitates, the displacement of the interface state(s) toward shallower positions, together with the reduction of the potential barrier, are interpreted in terms involving the increasing contribution of A‐type plates with their low BH in addition to that of B‐type silicides with their high BH.

Deep-level transient spectroscopy measurements have been performed on the quaternary semiconductor InGaAsN. A series of as-grown and annealed metalorganic chemical-vapor-deposited and molecular-beam-epitaxy samples with varying composition were studied. We observed a deep hole trap with activation energy ranging between 0.5 and 0.8 eV in all samples. The data clearly obey the Meyer–Neldel rule (MNR) with an isokinetic temperature of 350 K. We show that great care must be used in extracting capture cross sections (σ) from materials that obey the MNR. In fact, we argue that it is probably not possible to determine σ from the detrapping rate alone. One must measure both trapping and detrapping rates.

Software‐supported switching between the deep‐level transient spectroscopy (DLTS) and feedback charge method (FCM) operation modes of a versatile time‐domain spectrometer, while using identical circuitry, is demonstrated. No additional correction of the output signal for integrated leakage current is needed. The timing scheme design is discussed in more detail with reference to a practical example. The interval of achievable rate windows is not affected by the switching between the DLTS and FCM modes of the instrument. A few illustrative examples of DLTS and C‐V plots are included.

The conventional deep‐level transient spectroscopy (DLTS) analysis for Schottky diodes is based on the assumption that the relaxation processes in the space‐charge layer are governed by the thermal emission processes of majority carriers from deep‐level defects. It is shown in this article that this assumption cannot be justified for near midgap level defects in Schottky diodes with relatively low barrier heights, i.e., with high leakage current densities. In such cases, three thermal processes in the depletion layer have to be taken into account: the majority‐ and minority‐carrier emission processes and the majority‐carrier capture processes. It is shown that the conventional analysis of DLTS spectra based on the peak data leads to significant errors in the calculated deep‐level defect parameters. A numerical procedure for analysis of the DLTS spectra including the three above mentioned processes is proposed to determine the accurate values of near midgap level defect parameters.

Deep-level transient spectroscopy measurements in InAs quantum dots (QDs) grown in both n-GaAs and p-GaAs show that tunneling is an important mechanism of carrier escape from the dots. The doping level in the barrier strongly affects the tunneling emission rates, enabling or preventing the detection of a transient capacitance signal from a given QD level. The relative intensity of this signal acquired with different rate windows allows the estimation of tunneling emission energies.

The behavior of detector-grade Cd0.9Zn0.1Te in a radiation-hostile environment has been investigated by studying the effects on the material defective states induced by γ irradiation. The detector performance is strongly affected by the presence of charge-trapping centers which may also intervene in the material compensation properties. We have investigated by photoinduced current transient spectroscopy analyses the evolution with increasing irradiation dose of the deep levels both present in the as-grown material and induced by the ionizing radiation. A significant correlation between the material resistivity and some deep levels behavior has been observed. We have compared this trend to the results obtained from γ-irradiated CdTe:Cl to better understand the role deep traps play in the compensation process of II–VI materials.

We show that the usual Arrhenius analysis of the main electron-irradiation-induced defect trap in n-type GaN, observed by deep-level transient spectroscopy (DLTS), is not sufficiently accurate. Instead, an exact fitting of the DLTS spectrum for this trap reveals two components, each of which has a thermal energy near 60 meV, not the apparent 140–200 meV, as given in other DLTS studies. This result resolves the discrepancy between Hall-effect and DLTS determinations of the thermal energy of this defect center.

Deep‐level transient spectroscopy (DLTS) measurements of capture cross sections of Co60 induced silicon‐silicon dioxide (Si/SiO2) interface states have been performed. For the accurate analysis of measured data a new technique based on numerical solutions of the emission rate equations has been used. Computer simulations of DLTS measurements have been compared with measured data in order to extract reliable results in the case of nonexponential transients. We show that the capture cross sections are thermally activated. Together with earlier consistent results on the same kind of centers, this leads us to the conclusion that vibronic properties play important roles for the electron capture into these traps.

Undoped n‐GaAs with a 300 K resistivity between 10−1 and 108 Ω cm (electron concentration between 1×107 and 5×1015 cm−3 ) grown in quartz crucibles by the liquid‐encapsulated Czochralski (LEC) technique was investigated by thermally stimulated current (TSC), temperature‐dependent Hall effect (TDH), and deep‐level transient spectroscopy (DLTS). Using Schottky contacts the TSC method could be extended to medium‐resistivity samples. The strongly varying electron concentrations are correlated to varying TDH activation energies. The correlation between the donors dominating the electrical equilibrium properties and the electron traps detected by TSC and DLTS is discussed. Medium‐deep and deep levels are present in this LEC material in such high concentrations that they must be taken into account in the compensation mechanism.

Capacitance-frequency measurement is used to study In0.12Ga0.88As/GaAs p-i-n superlattice, with superlattice layer grown at 300 °C by molecular-beam epitaxy. Three traps are observed, and their parameters are consistent with those obtained from deep-level transient spectroscopy. Among these three traps, the trap (Ea=0.45±0.02 eV, σ=6±4×10−17 cm2) shows an abnormal increase of capacitance with increasing frequency, similar to that observed from the 0.66 eV trap in low-temperature grown GaAs p-i-n structure, suggesting that it is created by the low-temperature growth and is a generation-recombination center. This result also shows that the capacitance-frequency measurement is effective in studying the generation-recombination centers.

The correspondence between the E2 level (∼Ec−0.55 eV) in n-type GaN undergoing thermoionization and photoionization was established. The optical cross section in the vicinity of the threshold for photoionization of this level was measured by means of capacitance transient spectroscopy. Analysis using the formulation of Chantre yielded the optical activation energy, Eo=0.85 eV, and the Franck–Condon parameter, dFC=0.30 eV at 90 K.The correspondence between the E2 level (∼Ec−0.55 eV) in n-type GaN undergoing thermoionization and photoionization was established. The optical cross section in the vicinity of the threshold for photoionization of this level was measured by means of capacitance transient spectroscopy. Analysis using the formulation of Chantre yielded the optical activation energy, Eo=0.85 eV, and the Franck–Condon parameter, dFC=0.30 eV at 90 K.

Defects in Zn1−xMgxSe have been studied using deep-level transient spectroscopy. The crystalline material with low Mg concentration (x=0.09, 0.15), obtained by the high-pressure Bridgman method, has a sphalerite structure and shows n-type conductivity. A major electron trap was found with a thermal activation energy of 0.37 eV (x=0.09) and 0.38 eV (x=0.15), respectively. The trap concentration was 1.5–2.7×1014 cm−3. From capture measurements we obtained the electron capture rate cn as a function of the temperature, providing information about the thermal activation energy of the capture process. The capture barrier ΔEb splits into a high-temperature section with Eb=145 meV and a low-temperature section with a value of 66 meV for Eb. It is assumed that the predominant trap in Zn1−xMgxSe has the same origin as the well-known ∼0.32 eV trap in ZnSe.

Discrete electronic states at the inverted AlAs/GaAs interface grown by molecular beam epitaxy are identified by deep-level transient spectroscopy and capacitance-voltage measurements. The formation of two deep traps at the inverted AlAs/GaAs interface is shown to be related to the AlAs growth mode. We attribute the deep levels to intrinsic defects which are accumulated at the inverted AlAs/GaAs interface. The total density of interfacial electron traps can be minimized by growing AlAs in the pseudo-two-dimensional mode at a comparatively low temperature of 550 °C.

We report that the Te donor forms a deep level and acts as a DX center in In1−xGaxAsyP1−y/GaAs0.61P0.39. The characteristics of Te‐related deep level is investigated by deep‐level transient spectroscopy and thermally stimulated capacitance measurements. The deep level has a thermal activation energy of 0.14±0.01 eV regardless of the alloy composition of In1−xGaxAsyP1−y. Persistent photoconductivity is observed at low temperature in all Te‐doped In1−xGaxAsyP1−y/GaAs0.61P0.39 samples. The compositional dependence of deep trap density is explained by the energy difference between the conduction band minimum and the DX level.

We report a two‐step growth process, using an atomic layer epitaxially grown GaAs predeposition layer for the growth of GaAs/Si layers by metalorganic vapor phase epitaxy technique. Photoluminescence and deep‐level transient spectroscopy techniques are used to show that the quality of the grown material is comparable to that grown by a much complicated procedure involving strained layer superlattice buffers introduced between the active GaAs layer and the Si substrate.

Through temperature‐dependent conductivity measurements, we show evidence of a deep trap level in low‐temperature (LT) Al0.3Ga0.7As layers with an activation energy of ∼0.96 eV. This energy is near that of EL2‐like defects found previously in ‘‘normal’’ epitaxial Al0.3Ga0.7As. It is also considerably larger than the 0.70 eV value typically associated with defects in LT GaAs, which may explain the observed large resistivity (≳1011 Ω cm) in LT Al0.3Ga0.7As. Current transient spectroscopy (CTS) of these samples yields a deep level activation energy of 1.01 eV, in close agreement with the value obtained from conductivity measurements.

Two different kinds of n‐type GaN films were prepared by organometallic vapor phase epitaxy, one by using trimethylgallium (TMGa) and another by using triethylgallium (TEGa) as the alkyl source. Schottky diodes with well‐behaved current–voltage and capacitance–voltage characteristics were fabricated. Deep‐level transient spectroscopy studies were performed on these samples. Three distinct deep levels, labeled E1, E2, and E3, were measured in the film grown with TMGa, with an activation energy of 0.14, 0.49, and 1.63±0.3 eV, respectively. Only one level, E3, was observed in the film prepared with TEGa.

Two deep electron traps induced by lattice mismatch in relaxed GaAs1−xSbx layers (x=0% to 3%) grown by liquid phase epitaxy (LPE) on GaAs substrates have been revealed by means of deep‐level transient spectroscopy. One of the traps, that shows nonstandard, logarithmic capture kinetics and whose energy level is tied to the valence‐band edge, has been related to electron states associated with α dislocations. The other trap has been attributed to the EL2 defect and possible reasons of its unexpected formation in the LPE‐grown layers are briefly discussed.

The electrical properties of molecular beam epitaxy (MBE) grown low‐temperature GaAs (LT‐GaAs) by current transient spectroscopy (CTS) has been investigated. At least three deep traps have been observed in LT‐GaAs grown at 250 °C and annealed at 600 °C. The deepest level is dominant and has an activation energy of 0.82 eV, which is the same as that of the midgap donor, EL2. This is consistent with the activation energy of resistivity of this sample (0.77 eV), which is close to that for bulk nondoped semi‐insulating wafers. These results indicate that the Fermi level of annealed LT‐GaAs grown at 250 °C is pinned by the deep level at the midgap that is generally ascribed to AsGa antisite defects.

The effects of (NH4)2Sx solution treatment on the interface properties of metal‐In0.5Ga0.5P Schottky contacts have been investigated by capacitance‐voltage measurements and deep‐level transient spectroscopy measurements. The (NH4)2Sx‐treated samples show Schottky barrier heights that are more sensitive to the metal work functions. It is also found that (NH4)2Sx treatment of In0.5Ga0.5P can passivate the phosphorus‐vacancy‐related interface deep traps of Schottky contacts as well as suppress the generation of interface deep traps due to heat treatment.

The effect of iron charge state on its diffusion in p‐type Si near room temperature has been investigated by C–V and depth dependent deep‐level transient spectroscopy measurements. The migration enthalpies of both positively charged and neutral iron were found to be 0.92 and 0.56 eV, respectively. Disagreement between the theoretical predictions and experimentally observed trend in iron diffusion is briefly discussed in terms of diffusion path, elastic strain, and Coulombic interaction versus impurity charge state.

Combining deep level transient spectroscopy (DLTS), high-resolution Laplace DLTS, and minority carrier transient spectroscopy studies, we question the identification of the dominant Ti-related defects introducing deep levels (E40, E150, and H180) in n- and p-type Si. The observed results cannot unambiguously support the models previously reported for these defects. The presence of the Poole-Frenkel effect describing the enhancement of the emission rates of E40 as a function of electric field is not consistent with the previous assignment of this defect to the single acceptor, whereas the absence of the enhancement of the emission rate of E150 under different reverse bias applied to the diode does not confirm the previous attribution of this defect to the single donor in n-type Si. The attribution of H180 to the double donor is in good agreement with our results. In contrast, the identical depth profiles obtained for E40 and E150 in bulk of as-grown, hydrogenated and annealed samples cannot be explained by the assignment of these levels to different defects.

A GaP n+p-diode containing In0.5Ga0.5As quantum dots (QDs) and an AlP barrier is characterized electrically, together with two reference samples: a simple n+p-diode and an n+p-diode with AlP barrier. Localization energy, capture cross-section, and storage time for holes in the QDs are determined using deep-level transient spectroscopy. The localization energy is 1.14(±0.04) eV, yielding a storage time at room temperature of 230(±60) s, which marks an improvement of 2 orders of magnitude compared to the former record value in QDs. Alternative material systems are proposed for still higher localization energies and longer storage times.

We fabricate 2.6 μm InGaAs photodetectors by MBE technology and study its dark current mechanisms. Deep-level transient spectroscopy (DLTS) demonstrates a deep-level trap located at Ec - 0.25 eV in the absorption layer. Using the trap parameters, a dark current model is constructed and the device simulation generates the dark current characteristic which agrees well with the experimental data. The model suggests that the dark current at low reverse voltage is dominated by the Shockley-Read-Hall (SRH) and trap-assisted tunneling (TAT). Furthermore, it predicts some basic rules for suppressing the dark current in 2.6 μm InGaAs detectors.

Photoinduced current transient spectroscopy has been used to show the effect of thermal annealing on deep level defects in semi‐insulating Fe doped InP wafers. The annealing experiments have been accomplished in an infrared image furnace during 15 min at temperatures ranging from 663 to 820 °C. We show that this treatment leads to the formation of four deep traps named T1–T4 having the following activation energies: 0.14, 0.21, 0.41, and 0.53 eV, respectively. We show that the thermal anneal at high temperature leads to deterioration of the electrical properties of the material.

A new single scan method for obtaining deep level trap parameters is presented. This method represents an improvement over previous single scan approaches because it does not involve numerical analysis and it uses data over the entire temperature range of the deep‐level transient spectroscopy peak. Data are presented for an isolated deep level, the E center. The usefulness of this new method is also demonstrated by an example of successful analysis of overlapping deep level signals. The new single scan method maintains the simplicity of the traditional method of data collection. However, the single temperature scan saves time and more important, is often more accurate than the traditional multitemperature scan technique.

We have found by resistivity measurements and deep‐level transient spectroscopy that four kinds of oxygen‐related shallow donors, OD1–OD4, successively appear around 500 °C in the time region 10–106 min and carbon greatly affects their generation behavior in Czochralski silicon. The formation of OD2 and OD3 donors was enhanced by the presence of carbon, while that of OD1 and OD4 donors was retarded. The OD1 donor is identified as the so‐called thermal donor that consists of several kinds of double donors observed so far by infrared studies. The OD2 donor is a new kind of donor discovered recently by us. OD3 and OD4 donors, which were formed by very prolonged annealing around 500 °C, are suggested to have correlations with so‐called new donors normally generated above 600 °C. The origins of these oxygen‐related donors are discussed in relation to oxygen precipitation.

The detector performance and presence of Te secondary-phase defects distribution were investigated in CdMnTe (CMT) crystals prepared with different cooling rates. Detectors fabricated from fast-cooled CMT crystals exhibit a relatively poor detector performance, although IR transmission microscopy measurements show that the Te secondary-phase defects have a lower concentration and smaller size compared to slow-cooled crystals. Current deep-level transient spectroscopy (I-DLTS) measurements for both CMT detectors reveal the same trap levels, but there is a clear difference in the densities for the 0.26- and 0.42-eV traps for the two different cooling schemes. These two traps are probably attributed to Cd vacancies and Te anti-site defects, respectively. In addition, there is some likelihood that the traps are anti-correlated with respect to each other.

The localization energies, capture cross sections, and storage times of holes in GaSb quantum dots (QDs) are measured for three GaSb/GaAs QD ensembles with different QD sizes. The structural properties, such as height and diameter, are determined by atomic force microscopy, while the electronic properties are measured using deep-level transient spectroscopy. The various QDs exhibit varying hole localization energies corresponding to their size. The maximum localization energy of 800 (±50) meV is achieved by using additional Al0.3Ga0.7As barriers. Based on an extrapolation, alternative material systems are proposed to further increase the localization energy and carrier storage time of QDs.

A closed-cycle flow cell system was designed and built for application in ultrafast laser spectroscopy. The system features small cycle volume of down to less than 200 μl, adjustable beam path length, and compatibility with a large variety of solvents. The construction principle is simple, reliable, and versatile. The thickness and material of the windows can be easily exchanged to meet different demands of femtosecond spectroscopy. The flow rate is sufficient to allow complete sample exchange for measurements with a kHz repetition rate.