Investigation of DX centers in modulation-doped field-effect transistor-type Al0.3Ga0.7As/GaAs heterostructures using a fourier-transform deep level transient spectroscopy system

Al_0.3Ga_0.7As:Si/GaAs modulation-doped field-effect transistor-type heterostructures were grown using two different growth temperatures (500 and 620°C) and three doping modes (δ-doping, pulse-doping, and uniform-doping). Deep level transient spectroscopy (DLTS) measurements were performed on these structures using a new Fourier-analysis method. Up to four DLTS peaks, related to the different possible configurations of the nearest Al and Ga neighbors around each DX site, were observed. Both the growth temperature and the doping-mode are found to affect the DLTS spectra, in particular the number of observed peaks and their width. These results are interpreted in terms of the different mobilities of the Si doping atoms on the surface during growth.     

Electrical characterization of self-assembled In0.5Ga0.5As/GaAs quantum dots by deep level transient spectroscopy

We have investigated electron emission from self-assembled In_0.5Ga_0.5As/GaAs quantum dots (QDs) grown by molecular-beam epitaxy (MBE). Through detailed deep level transient spectroscopy comparisons between the QD sample and a reference sample, we determine that trap D, with an activation energy of 100 meV and an apparent capture cross section of 5.4×10⁻¹⁸ cm², is associated with an electron quantum level in the In_0.5Ga_0.5As/GaAs QDs. The other deep levels observed, M1, M3, M4, and M6, are common to GaAs grown by MBE.     

Deep level transient spectroscopy study of electron-irradiated CuInSe<Subscript>2</Subscript> thin films

Irradiation of high-energy (2-MeV and 3-MeV) electrons on single-crystalline n-CuInSe₂ films has been investigated. From Hall-effect measurements of the film, the carrier density and mobility were decreased by increasing the electron fluence above 1×10¹⁷ cm⁻². In both as-grown and electron-irradiated CuInSe₂ films, the deep level transient spectroscopy (DLTS) peak, indicating electron trap, was found at around 180 K. However, Arrhenius plots of the observed DLTS peaks in as-grown and electron-irradiated films showed different behavior, suggesting the presence of electron traps introduced by high-energy electron irradiation.     

Semiconductor steady state defect effective Fermi level and deep level transient spectroscopy depth profiling

The widely used deep level transient spectroscopy (DLTS) theory and data analysis usually assume that the defect level distribution is uniform through the depth of the depletion region of the n-p junction. In this work we introduce the concept of effective Fermi level of the steady state of semiconductor, by using which deep level transient spectroscopy depth profiling (DLTSDP) is proposed. Based on the relationship of its transition free energy level (TFEL) and the effective Fermi level, the rules of detectivity of the defect levels are listed. Computer simulation of DLTSDP is presented and compared with experimental data. The experimental DLTS data are compared with what the DLTSDP selection rules predicted. The agreement is satisfactory.     

A deep level transient spectroscopy study of rapid thermal annealed arsenic implanted silicon

Deep level traps are observed in silicon that has been implanted with high doses of arsenic and subsequently annealed by rapid thermal annealing. The doses studied create enough damage to form a surface amorphous layer. Annealing temperatures, implant fluence, and the presence of a surface amorphous layer contribute to the type of trap observed. These results show evidence for a clustering/declustering mechanism of arsenic in silicon during rapid thermal annealing.     

Digital deep level transient spectroscopy considered for discrimination of traps closely spaced in emission coefficients in semiconductors

A method is presented for analysis of digitally recorded capacitance transients to give activation energies and capture cross-sections of two deep levels which would yield overlapping peaks in conventional DLTS spectra. It is shown that baseline errors can be overcome by proper analysis of the data. The accuracy of the method is examined by simulation with parameters representative of a typical DLTS system. The addition of various noise levels is also simulated and the effects of averaging of transients on the ability to discriminate closely spaced traps is examined quantitatively.     

Inhomogeneity of the deep center el2 in GaAs observed by direct infra-red imaging

The distribution of the dominant deep trap EL2 in 7.5cm diameter crystals of semi-insulating GaAs is studied by whole slice infrared imaging. Very significant fluctuations in the neutral EL2 concentration ([EL2]ℴ) are observed, corresponding at most to variations in [EL2]ℴ of up to 80%. The different sorts of fine structure, namely cell structure and bands of high infrared absorption ("sheets" and “streamers”) lying in (110) planes running down the <001> growth directions, are described.     

EL2能级和光电离截面的计算

我们采用EHT法计算了EL2缺陷模型的电子能级及其波函数,集团包含41个原子,用群论方法约化久期行列式。同时计算了该缺陷能级的光电离截面,计算结果与实验结果相符。     

Observation of differences in the quenching of the Photocurrent in GaAs containing EL2 and EL0

The quenching of the photocurrent and photo-Hall effect of several undoped semi-insulating gallium arsenide samples has been measured and compared with the deep-level photoluminescence spectra from neighboring samples. Samples that show either EL2 (0.68 eV) or ELO (0.63 eV) photoluminescence have distinctly different photocurrent quenching behaviors. EL2 samples show a photocurrent decrease of several orders of magnitude, and a change fromn-type to p-type conduction during quenching at 80 K with 1.1 eV light. ELO samples show a reduction in photocurrent of less than an order of magnitude with no change in the carrier type at this temperature. Photo-Hall effect experiments at 80 K indicate that the conduction isn-type for the ELO samples, but changes fromn- to p-type during the quench for the EL2 samples. The temperature dependence of the quenching has also been studied. EL2 samples show little variation in the range 10-80 K, while ELO samples show significant quenching similar to EL2 after the temperature is reduced below 70 K. These results indicate that defects other than EL2 can significantly affect photocurrent quenching experiments.     

Metastable population of self-organized InAs/GaAs quantum dots

In the present work, we report on the investigation of a p-n heterostructure with InAs/GaAs quantum dots (QD) by capacitance-voltage and deep level transient spectroscopy. We have observed controllable and reversible metastable population of the energy states of quantum dots and interface in the structure containing one plane of InAs QDs as a function of temperature of isochronous annealing as well as under bias-on-bias-off cooling conditions and white light illumination. This effect was attributed to the change in the Fermi level position due to the hole capture on self-trapped defects similar to the DX center in GaAs after isochronous annealing and white light illumination.     

未掺杂半绝缘GaAs中受主及电中性EL2分布的研究

测量了未掺杂半绝缘（ＳＩ）ＬＥＣＧａＡｓ中总的、电中性的ＥＬ２及净受主浓度分布和碳分布。结果表明，总ＥＬ２浓度径向分布呈Ｗ形而不是均匀的，净受主浓度径向分布呈∧形或∩形而不是Ｍ形。电中性ＥＬ２的Ｗ形径向分布由总ＥＬ２浓度的Ｗ形径向分布决定，而不是由于净受主的不均匀分布。有些样品中净受主浓度远大于碳浓度．意味着这些样品中除碳外还存在高浓度的其它受主。     

Effects of electrode geometry and polarity on the occurrence of negative peaks in optical transient current spectroscopy applied to semi-insulating gallium arsenide

Optical transient current spectroscopy (OTCS) involves observing the transient decay of “photoconductivity” and is of interest as a means of characterizing semi-insulating GaAs wafers. We report experimental results which show that the OTCS spectrum and, in particular, the occurrence of negative peaks is strongly dependent on the shape, size and electrode configuration of the specimen, as well as on the magnitude of the applied voltage and (with asymmetric electrodes) its polarity. A negative peak sometimes changes to a current oscillation with increasing voltage, probably indicating field enhanced trapping. Negative peaks may be observed with sandwich structures with a transparent electrode covering the illuminated surface. This shows that a recent proposal that surface states are involved is at least not always correct. It is suggested that several mechanisms can give negative peaks, and probably more than one has done so under the various experimental conditions which have been used. The present work shows that any practical application of OTCS for ingot qualification will be dependent on standardization of specimen geometry, electrodes and operating parameters.     

Cathodoluminescence spectroscopy of deep defect levels at the ZnSe/GaAs interface with a composition-control interface layer

In this work we investigate ZnSe/GaAs heterostructures with an additional 2 nm controlled interfacial layer (CIL) of Se- or Zn-rich composition to modify the band offset. The samples are analyzed as a function of annealing temperature by cathodoluminescence spectroscopy. The as-prepared samples show defect luminescence at ∼ 0.9 eV. With staged annealing at increasing temperatures, both the Zn-rich as well as the Se-rich interfacial layer exhibits luminescence at ∼ 1.9 eV, indicative of defect formation with an onset temperature of ∼400°C. Excitation-dependent spectroscopy provides evidence for defect formation near the interface, which extends into the ZnSe epilayer at higher temperatures. Compared to earlier work, where the threshold temperature for defect formation in bulk samples fabricated under Se-rich growth conditions occurs at temperatures as low as 325°C, the resistance to defect formation has now been improved to that of stoichiometric ZnSe. These results demonstrate that epitaxially grown CILs provide a means to alter ZnSe/GaAs band offsets without degrading the heterojunction’s resistance to defect formation at elevated temperatures.     

MOCVD生长的未掺杂的In1－xGaxP中的本征缺陷

利用深能级瞬态谱(DLTS)和瞬态光电阻率谱(TPRS)研究了利用金属有机物化学气相沉淀(MOCVD)方法生长的未有意掺杂的In     

A study of deep levels in GaAs by capacitance spectroscopy

We show how the DLTS capacitance spectroscopy technique can be used to detect small amounts of deep level impurities in GaAs p-n junctions. The DLTS spectra associated with Cu, Fe, Cr, 0, and two unidentified but commonly occurring deep levels in GaAs are shown. The LPE distribution coefficients are obtained for Cu, Fe, and Cr. The carrier capture cross sections for six levels are measured and give evidence for capture by multiphonon emission.     

GaAs对脉冲Nd:YAG激光器的调Q和锁模

本文分析半导体材料GaAs对1064nm激光的可饱和吸收特性,在闪光灯抽运的平凹腔和平凸腔Nd:YAG激光器中,插入GaAs样品作为调Q器件,实现了激光器的被动调Q运转,分别获得脉冲宽度32.7ns(平凹腔)和30.9ns(平凸腔)的激光脉冲。实验上研究了平凹腔腔长和输出镜透过率对调Q激光输出性能的影响。当平凹腔腔长增加到125cm时,观察到GaAs对1064nm激光的被动锁模。对上述实验结果给予了合理的理论解释。     

MOCVD生长的未掺杂的In1-xGaxP中的本征缺陷

利用深能级瞬态谱（ Ｄ Ｌ Ｔ Ｓ）和瞬态光电阻率谱（ Ｔ Ｐ Ｒ Ｓ）研究了利用金属有机物化学气相沉淀（ Ｍ Ｏ Ｃ Ｖ Ｄ）方法生长的未有意掺杂的 Ｉｎ１－ ｘ Ｇａｘ Ｐ中缺陷对载流子的俘获和发射过程。利用 Ｄ Ｌ Ｔ Ｓ测量观测到了一个激活能为０３５ ｅ Ｖ 的缺陷,由 Ｔ Ｐ Ｒ Ｓ测量确定该缺陷的俘获势垒值介于１８０ ｍ ｅ Ｖ 到２４０ｍ ｅ Ｖ 之间。该缺陷的俘获势垒值的大的分布解释为缺陷周围原子重组的微观波动。同时在 Ｔ Ｐ Ｒ Ｓ测量中观测到俘获势垒为００６ ｅ Ｖ 和０４０ ｅ Ｖ 的两个缺陷。     

DETERMINATION OF TOTAL EL2 AND NET ACCEPTOR CONCENTRATION IN UNDOPED SI GaAs BY MULTI-WAVELENGTH INFRARED ABSORPTION METHOD

Total EL2 concentration distribution and net acceptor concentration distribution in uncloped semi-insulating(SI) LEC GaAs have been measured by multi-wavelength infrared absorption method. The experimental results indicate that total EL2 concentration radial distribution is W-shaped and net acceptor concentration radial distribution is sample-dependent, it can present a n shape, a A shape, or a W shape corresponding to different samples.     

Role of contacts in characterization of deep traps in semi-insulating GaAs by thermally stimulated current spectroscopy

The role of contacts in characterization of traps in semi-insulating (SI) GaAs by thermally stimulated current (TSC) methods has been demonstrated by comparing alloyed In and soldered In contacts. Alloyed In contacts, which have an ohmic characteristic, assure high sensitivities in both TSC and temperature dependent photocurrent (PC), and both are important for determining the trap concentrations in SI GaAs. On the other hand, soldered In contacts, which act like Schottky barriers, cause a significant reduction of both PC and TSC, particularly at low temperatures, and can lead to a misinterpretation of TSC results.     

Excitonic recombination processes in GaAs grown by close-space vapour transport

Epitaxial GaAs layers were grown using the close-space vapour transport. From deep level transient spectroscopy measurements, the native EL2 donor has been observed in all of the layers with deposition temperature-dependent concentration. On the GaAs samples, also performed are photoluminescence experiments in the temperature range 10-300 K. Two peculiar features were revealed: (i) the radiative recombination in GaAs layers is increasingly dominated by bound-exciton transitions, (ii) the excitonic luminescence is found to be very sensitive to the growth conditions. A study of the near-band-edge photoluminescence as a function of power excitation and temperature has been done in an attempt to elucidate the origin of the enhanced bound-exciton luminescence.