AlGaAs:Si中与DX中心有关的光生电子陷阱特性研究(英文)

A new electron trap state SD was found by DLTS measurement under light illumination in Si doped A.lxGa1-xAs. This new trap energy level ESD is shallower than the DX center energy in the gap and the concentration of SD is comparable to that of DX centers. The emission activation energy Ec=0.20±0.05eV and capture activation energy Ec= 0.17±0.05eV. The SD DLTS peak has never been detected previously because under dark and thermal equilibrium condition most of the electrons occupy the deeper DX states and most of SD states are empty. However, when the sample is illuminated by light, electrons are excited to the conduction band and then re-captured by SD since the deeper DX states have a slower electron capture rate, thus a new DLTS peak corresponding to SD appears. Constant temperature capacitance transient C-t and transient C-V measurements were also used to further confirm the existence of SD states.     

瞬态C-V方法对Al_xGa_(1-x)As中DX中心的研究

本文指出DX中心电容测量中边区的重要性,提出一种新的瞬态C-V方法,可以用来测量DX中心浓度、导带电子浓度和边区的空间电荷分布及导带电子浓度随温度的变化关系,并由此导出测量DX中心热电离能的方法。另外,还对DX中心正∪和负∪两种模型的理论分析和实验结果进行了比较,得出不同模型所应满足的附加条件。     

DX-center energy level dependence on silicon doping concentration in Al0.3Ga0.7As

The Hall free carrier concentration of silicon-doped Al_0.3Ga_0.7As alloys is studied as a function of both temperature and illumination. Different thermal activation energies were observed for the DX center as a function of silicon concentration. Excitation of the samples using an infra-red source also provided data for better insight into the DX center population. We correlated the incremental free electron photo persistent population with the activation energies obtained from the temperature dependence of the measured Hall concentration. We concluded that large free carrier concentrations can yield perturbations in the lattice potential that may alter the configuration coordinate energy barriers for capture and emission of electrons by and from the DX centers.     

Thermal capture of electrons and holes at zinc centers in silicon

The thermal capture rates of electrons and holes at zinc centers in silicon are obtained in reversed biased N⁺P and P⁺N diodes from junction capacitance transients due to capture of photogenerated and injected carriers. The electric field dependence of the thermal capture rates of holes at singly ionized zinc centers is E^?1·1, while that at doubly ionized zinc centers is exp(?E/E₀). The temperature dependence of the thermal capture rate of holes at doubly ionized zinc centers is small. The thermal capture rate of electrons at neutral zinc centers is 2·0×10^?9cm³/sec with very little field dependences, while that at singly ionized zinc centers is 5·0×10^?11cm³/sec with very little field and temperature dependence below 170°K. Auger-impact emission rate of electrons trapped at doubly ionized zinc centers by electrons is 3·5×10^?10cm³/sec with very little field and temperature dependence below 170°K.     

A novel transient characterization technique to investigate trap properties in HfSiON gate dielectric MOSFETs-from single electron emission to PBTI recovery transient

A positive bias temperature instability (PBTI) recovery transient technique is presented to investigate trap properties in HfSiON as high-k gate dielectric in nMOSFETs. Both large- and small-area nMOSFETs are characterized. In a large-area device, the post-PBTI drain current exhibits a recovery transient and follows logarithmic time dependence. In a small-area device, individual trapped electron emission from HfSiON gate dielectric, which is manifested by a staircase-like drain current evolution with time, is observed during recovery. By measuring the temperature and gate voltage dependence of trapped electron emission times, the physical mechanism for PBTI recovery is developed. An analytical model based on thermally assisted tunneling can successfully reproduce measured transient characteristics. In addition, HfSiON trap properties, such as trap density and activation energy, are characterized by this method.     

Relaxation of parameters of thin-film electroluminescent ZnS:Mn-based structures when turned off

Results of experimental study of decay of the current flowing through a thin-film electroluminescent MISIM structure indicate a bimolecular process of electron capture by the surface states of the anode interface. A two-stage model of the process is suggested. At the first stage, the impact Auger capture of hot electrons takes place. At the second stage, upon varying the field direction, the holes of the valence band generated due to tunnel emission from deep centers drift to this interface, where they recombine with electrons of deepest occupied surface states. The electron lifetime and rate of the surface capture of electrons as well as their dependences on excitation parameters are determined. The behavior of the time dependence of the instant internal quantum yield at the decay portion is interpreted.     

On the carrier emission from donor-related centres in GaAs1-xPx and AlxGa1-xAs

From an experimental study of the electron thermal emission and capture rates of Te-related centres, donor-related (DX) traps have been identified in GaAsP and GaAlAs compounds. It is shown that under thermal excitation nonexponential transient waveforms markedly deviate from theory. The relation of the nonexponential degree with alloy composition and junction electric field has been studied. In addition, optical activated transients, a model based on trap charge dependent emission and capture coefficients, and the drawbacks of Deep Level Transient Spectroscopy (DLTS) techniques to study DX centres are presented.     

Study of deep-level defects and annealing effects in undoped and Sn-doped GaAs solar cells irradiated by one-MeV electrons

DLTS and C-V techniques have been employed to determine the defect energy levels and density, carrier capture cross sections, lifetimes and diffusion lengths in the Sn-doped and the undoped GaAs solar cells irradiated by one-MeV electrons under different electron fluences (10¹⁴ to 10¹⁶ cm^?2), fluxes (2 × 10⁹, 4 × 10¹⁰ e/cm²-s), and annealing conditions (150 ? T ? 230°C). The results show that density of both electron and hole traps will in general increase with incresing electron fluence and flux, and decrease with increasing annealing temperature and annealing time. Some distinct difference in defeat spectrum was observed in the undoped and the Sn-doped GaAs solar cells studied. The low temperature thermal annealing and the recombination enhanced annealing processes are found to be very effective in reducing the density of deep-level defects induced by one-MeV electrons. The results of our findings are discussed in detail in this paper.     

Deep level transient spectroscopy assessment of silicon contamination in AlGaAs layers grown by metalorganic vapor phase epitaxy

A systematic silicon contamination has been detected by deep level transient spectroscopy in undoped and n-type doped (Te, Se, Sn) AlGaAs layers, grown in two different metalorganic vapor phase epitaxy reactors. DX center generation by substitutional donors, with very specific capture and emission thermal barriers (fingerprints), is the key to unambiguously identifying their presence, with detection limits well below the standard secondary ion mass spectroscopy capability. We comment on the potential sources of Si contamination (most common in this epitaxial technique), and on the relevance of such contamination to interpreting correctly experimental data related to the microscopic structure of DX centers.     

HEMT-Al_(0.3)Ga_(0.7)As层中DX中心对器件电学特性的影响研究

本文通过改变温度和光照条件,研究了深能级DX中心的温度特性对HEMT器件的I—V,C—V特性及噪声系数的影响。由实验及理论计算分别得到了I—T,C—T,F—T等曲线。结果表明,DX中心上的带电状态在153～230K之间变化较大,这一温度范围内DX中心对器件的饱和电流,栅电容及噪声系数影响也较大。本文还直接在HEMT器件上作了DLTS测量,得到的结果和理论分析基本相符。