Intraband Dynamics and Terahertz Emission in Biased GaAs/In0.53Ga0.47As Semiconductor Superlattices

Using an excitonic basis, we investigate the intraband polarization, optical absorption spectra, and terahertz emission of semiconductor superlattice with the density matrix theory. The excitonic Bloch oscillation is driven by the dc and ac electric fields. The slow variation in the intraband polarization depends on the ac electric field frequency. The intraband polarization increases when the ac electric field frequency is below the Bloch frequency. When the ac electric field frequency is above the Bloch frequency, the intraband polarization downwards and its intensity decreases. The satellite structures in the optical absorption spectra are presented. Due to excitonic dynamic localization, the emission lines of terahertz shift in different ac electric field and dc electric field.     

The electronic structure of modulation-doped In0.53Ga0.47As/n-In0.52Al0.48As heterostructure

Summary The subband structure of modulation-doped InGaAs/InAlAs heterostructures is calculated in a variational self-consistent manner. The dependence on various device parameters is examined. The many-body exchange correlation effects are taken into account.     

Current Oscillation and dc-Voltage-Controlled Chaotic Dynamics in Semiconductor Superlattices

We report a detailed theoretical study of current oscillation and dc-voltage-controlled chaotic dynamics in doped GaAs/AlAs resonant tunneling superlattices under crossed electric and magnetic fields. When the superlattice is biased at the negative differential velocity region, current self-oscillation is observed with proper doping concentration. The current oscillation mode and oscillation frequency can be affected by the dc voltage bias, doping density, and magnetic field. When an ac electric field with fixed amplitude and frequency is also applied to the system, different nonlinear properties show up in the external circuit with the change of dc voltage bias. We carefully study these nonlinear properties with different chaos-detecting methods.     

XPS data for sputter-cleaned In0.53Ga0.47As,GaAs, and InAs surfaces

Core level binding energies and Auger parameters were determined for In, Ga, and As in the three compounds In_0.53Ga_0.47As, GaAs, and InAs. The surfaces were cleaned by 1.5 keV Ar ion bombardment. Under this condition the radiation-induced defects are small. In the case of GaAs the Ga and As3d levels become comparable with available data for chemically cleaned surfaces. The high Ga deficiency of chemically cleaned In_0.53Ga_0.47As surfaces could not be observed. Sputter cleaned surfaces seem to be closer to the bulk composition.     

p-i-nInP/In_(0.53)Ga_(0.47)As/InP探测器结构优化

利用半导体仿真工具Silvaco对p-i-n InP/In_(0.53)Ga_(0.47)As/InP近红外光探测器进行优化仿真.参考实际器件对红外探测器进行建模,并将其暗电流、光谱响应仿真结果与实验结果进行拟合,保证仿真结果的有效性.以减小探测器的暗电流为目的,优化其结构.针对探测器吸收层厚度和吸收层掺杂浓度对暗电流、光响应的影响进行研究,发现当吸收层厚度大于0.3μm后,暗电流不再上升,但光响应随着吸收层厚度的增加而增大;当吸收层掺杂浓度不断上升时,器件暗电流不断降低,当掺杂浓度上升到2×1017/cm3时,暗电流达到最低值.本文还研究了p-i-n型探测器的瞬态响应,探究了响应速度与反偏电压之间的关系,发现提高反偏电压能减小探测器响应时间.     

Metamorphic In0.53Ga0.47As p-I-n photodetector grown on GaAs substrates by low-pressure MOCVD

Top-illuminated metamorphic In0.53Ga0.47As p-i-n photodetectors are grown on the ultrathin lowtemperature InP buffered GaAs substrates. Photodetectors with the 300-nm-thick In0.53Ga0.47As absorption layer show a typical responsivity of 0.12 A/W to 1.55-μm optical radiation, corresponding to an external quantum efficiency of 9.6%. Photodetectors with the active area of 50 × 50 (μm) exhibit the -3 dB bandwidth up to 6 GHz. These results are very encouraging for the application of this metamorphic technology to opto-electronic integrated circuit (OEIC) devices.     

Two-dimensional electronic transport in In0.53Ga0.47As quantum Wells

Transport properties of the electrons itinerant two dimensionality in a square quantum well of In_0.53Ga_0.47As are studied in the framework of Fermi-Dirac statistics including the relevant scattering mechanisms. An iterative solution of the Boltzmann equation shows that the ohmic mobility is controlled by LO phonon scattering at room temperature, but below 130 K alloy scattering is predominant. The calculated mobilities with a suitable value of the alloy scattering potential agree with the experimental results over a range of lattice temperature. For lattice temperatures below 25 K where the carrier energy loss is governed by the deformation potential acoustic scattering, the warm electron coefficient is found to be negative. Its magnitude decreases with increasing lattice temperature and is greater for larger channel widths. Values of the small-signal AC mobility of hot electrons at a lattice temperature of 4.2 K are obtained for different sheet carrier densities and channel widths. Cut-off frequencies around 100 GHz are indicated.Dedicated to H.-J. Queisser on the occasion of his 60th birthday     

In0.53Ga0.47AS/In0.52Al0.48As量子阱中的正磁电阻效应

在低温强磁场条件下,对In0.53 Ga0.47 As/In0.52AI0.48As量子阱中的二维电子气进行了磁输运测试.在低磁场范围内观察到正磁电阻效应,在高磁场下这一正磁电阻趋于饱和,分析表明这一现象与二维电子气中的电子占据两个子带有关.在考虑了两个子带之间的散射效应后,通过分析低磁场下的正磁电阻,得到了每个子带电子的迁移率,结果表明第二子带电子的迁移率高于第一子带电子的迁移率.进一步分析表明,这主要是由两个子带之间的散射引起的.     

Incorporation behaviour of manganese in MBE grown Ga0.47In0.53As

Acceptor doping of MBE grown Ga_0.47In_0.53As on InP:Fe substrates utilizing manganese is investigated as an alternative for overcoming problems related to beryllium doping. The incorporation behaviour of manganese is analyzed in detail with respect to its application in optoelectronic device structures. Special emphasis is put on low-level and maximum-level doping relevant for use in buffer and contact layers, respectively. The dependence of activation energy and the degree of ionization on acceptor concentration is determined. At high doping levels the free-hole concentration is markedly lower than the doping concentration. It is attributed to the diffusion of acceptor species across the heterointerface into the substrate. Manganese diffusion is demonstrated to be an important effect for the interpretation of the measurement results. Manganese doping is applied in p⁺/n/p^–-layer structures for junction field effect transistor applications. The intended abruptness of acceptor profiles is deteriorated by diffusion of manganese in the Ga_0.47In_0.53As material. The degraded device characteristics obtained are attributed to the acceptor diffusion behaviour established.     

Dark current simulation of InP/In0.53Ga0.47As/InP p-i-n photodiode

We report on 2D simulations of dark current for InP/In_0.53Ga_0.47aAs/InP p-i-n photodiode. Our simulation result is in good agreement with experiment confirming that generation-recombination effect is the dominant source of the dark current at low bias. Effects of the thickness and doping concentration of the absorption layer on the dark current are discussed in detail.     

基于silvaco-TCAD的In0.53Ga0.47As/InP红外探测器的仿真

采用silvaco-TCAD研究In0.53Ga0.47As/InP SAGCM-APD光电探测器,对探测器的结构参数对器件的电场分布、击穿电压和贯穿电压的影响进行仿真分析。研究表明电荷层对器件内部电场起到更好的调节作用,但过高的电荷层面密度会导致APD探测器的击穿电压与贯穿电压之差减小。倍增层厚度的增加使击穿电压先减小后增高,贯穿电压线性增加,同时耗尽层宽度变大,使器件电容减小。当倍增区厚度1 μm、偏压为-5 V时,器件电容密度达到了4.5×10-17 F/μm。反向偏置电压为30 V时,APD探测器在1.31 μm和1.55 μm波长下的响应度分别达到1 A/W和1.1 A/W     

Spectrum analysis of interband optical transmissions and quantitative model of eigen-energies and absorptions in In0.53Ga0.47As/In0.52Al0.48As multi-quantum well structures

Interband transmission spectra were measured for three In_0.53Ga_0.47As/In_0.52Al_10.48As multi-quantum well specimens having different carrier concentrations by modulation-doping. Spectral shapes of transmissions were clear steplike structures but exciton peaks of first order transitions were masked with the carrier concentrations. The spectral shapes changed hardly between 100 and 310 K. Using our parameters of quantum wells, calculated eigen-energies for three specimens agreed with experiments and absorption coefficients reproduced experimental transmission spectra at any temperature.     

Study of single event effect for the InP-based HEMT with In0.53Ga0.47As/In0.3Ga0.7As/In0.7Ga0.3As composite channel

In this study, the single event effects in In_0.53Ga_0.47As/In_0.3Ga_0.7As/In_0.7Ga_0.3As composite channel InP-based HEMT are investigated using TCAD simulation for the first time. Due to the higher conduction band difference between bottom In_0.7Ga_0.3As channel and InAlAs buffer, the electrons in the buffer layer induced by ions strike cannot enter the channel, led to reduce the peak concentration in the composite channel and significantly weakened the drain current for composite channel device. Meanwhile, higher barrier height under the gate for composite channel InP-based HEMT is formed after particle strike, and further attenuate the drain current. Therefore, the single event effects can be effectively reduced by designing channel structure. In addition, drain voltage and incident position also show significant impact drain current. With the increase in the drain voltage, the drain current increase and the most sensitive incident position is the gate electrode for the device.     

Cation diffusion in InP/In0.53Ga0.47As superlattices: strain build-up and relaxation

InP and In_0.53Ga_0.47As are lattice matched and can form superlattices that are free of crystalline defects. Zn indiffusion enhances the diffusion of cations while leaving the anions unaffected; the resultant In_1–x Ga _x P/In_1–x Ga _x As superlattices are strained. Since the as-grown specimens are pseudomorphic, any defects observed after Zn diffusion must be attributed to strain relaxation. Studies of the post-growth strain build-up and relaxation in this novel system suggest a new strain relief mechanism for buried strained layers of face-centred-cubic (fcc) structures. The signature defect of the proposed mechanism is a microtwin along a {111} plane spanning the buried strained layer and terminating at both interfaces with partial dislocations of 1/6112 type. Energy analysis indicates that this new partial-dislocation strain relief mechanism is more effective than the conventional 60 perfect-dislocation mechanism for relieving the in-plane strain in buried strained layers. Therefore, the proposed mechanism is an energetically favourable relaxation channel and limits the useful thicknesses of strained layers in electronic and optoelectronic devices.     

Maskless photoassisted etching of N-type Ga0.47In0.53As in basic solutions

The maskless photoassisted etching of n-type Ga_0.47In_0.53As is examined for basic KOH solutions in comparison with GaAs and InP material. The etch rate increases with laser intensity and with carrier concentration up to a saturation value. The best etch rate is obtained with molar KOH in ethyl alcohol (7 ms^–1 for laser intensity 10⁴ W cm^–2). Selective etching have been realized on heterojunction in order to isolate p-n junctions without the help of masks.