Self-consistent analysis of double-δ-doped InAlAs/InGaAs/InP HEMTs

We have carried out a theoretical study of double-5-doped InAlAs/InGaAs/InP high electron mobility transistor （HEMT） by means of the finite differential method. The electronic states in the quantum well of the HEMT are calculated self-consistently. Instead of boundary conditions, initial conditions are used to solve the Poisson equation. The concentration of two-dimensional electron gas （2DEG） and its distribution in the HEMT have been obtained. By changing the doping density of upper and lower impurity layers we find that the 2DEG concentration confined in the channel is greatly affected by these two doping layers. But the electrons depleted by the Schottky contact are hardly affected by the lower impurity layer. It is only related to the doping density of upper impurity layer. This means that we can deal with the doping concentrations of the two impurity layers and optimize them separately. Considering the sheet concentration and the mobility of the electrons in the channel, the optimized doping densities are found to be 5 × 10^12 and 3× 10^12 cm^-2 for the upper and lower impurity layers, respectively, in the double-5-doped InAlAs/InGaAs/InP HEMTs.     

A 10.7 μm InGaAs/InAlAs Quantum Cascade Detector

A 10.7μm quantum cascade detector based on lattice matched InGaAs/InAlAs/InP is demonstrated and characterized in terms of responsivity, resistivity and detectivity. The device operates in the 8 14μm atmospheric window up to 140 K and shows a peak reponsivity of 14.4mA/W at 78K. With a resistance-area product value of 159Ωcm^2, the Johnson noise limited detectivity D^＊J is 2.8 × 10^9 Jones （cmHz^1/2W^-1） at 78K.     

Effects of proton irradiation at different incident angles on InAlAs/InGaAs InP-based HEMTs

InP-based high electron mobility transistors(HEMTs) will be affected by protons from different directions in space radiation applications. The proton irradiation effects on InAlAs/InGaAs hetero-junction structures of InP-based HEMTs are studied at incident angles ranging from 0 to 89.9° by SRIM software. With the increase of proton incident angle, the change trend of induced vacancy defects in the InAlAs/InGaAs hetero-junction region is consistent with the vacancy energy loss trend of incident protons. Namely, they both have shown an initial increase, followed by a decrease after incident angle has reached 30°. Besides, the average range and ultimate stopping positions of incident protons shift gradually from buffer layer to hetero-junction region, and then go up to gate metal. Finally, the electrical characteristics of InP-based HEMTs are investigated after proton irradiation at different incident angles by Sentaurus-TCAD. The induced vacancy defects are considered self-consistently through solving Poisson's and current continuity equations. Consequently, the extrinsic transconductance, pinch-off voltage and channel current demonstrate the most serious degradation at the incident angle of 30?, which can be accounted for the most severe carrier sheet density reduction under this condition.     

Physical modeling of direct current and radio frequency characteristics for In P-based InAlAs/InGaAs HEMTs

Direct current(DC) and radio frequency(RF) performances of InP-based high electron mobility transistors(HEMTs)are investigated by Sentaurus TCAD. The physical models including hydrodynamic transport model, Shockley–Read–Hall recombination, Auger recombination, radiative recombination, density gradient model and high field-dependent mobility are used to characterize the devices. The simulated results and measured results about DC and RF performances are compared, showing that they are well matched. However, the slight differences in channel current and pinch-off voltage may be accounted for by the surface defects resulting from oxidized InAlAs material in the gate-recess region. Moreover,the simulated frequency characteristics can be extrapolated beyond the test equipment limitation of 40 GHz, which gives a more accurate maximum oscillation frequency( f_(max)) of 385 GHz.     

Classical Effects in the Weak-Field Magnetoresistance of InGaAs/InAlAs Quantum Wells

We observe an unusual behavior of the low-temperature magnetoresistance of the high-mobility two-dimensional electron gas in InGaAs/InAlAs quantum wells in weak perpendicular magnetic fields. The observed magnetoresistance is qualitatively similar to that expected for the weak localization and antilocalization but its quantity exceeds significantly the scale of the quantum corrections. The calculations show that the obtained data can be explained by the classical effects in electron motion along the open orbits in a quasiperiodic potential relief manifested by the presence of ridges on the quantum well surface.     

Influences of increasing gate stem height on DC and RF performances of InAlAs/InGaAs InP-based HEMTs

The T-gate stem height of In Al As/In Ga As In P-based high electron mobility transistor(HEMT) is increased from165 nm to 250 nm. The influences of increasing the gate stem height on the direct current(DC) and radio frequency(RF)performances of device are investigated. A 120-nm-long gate, 250-nm-high gate stem device exhibits a higher threshold voltage(Vth) of 60 m V than a 120-nm-long gate devices with a short gate stem, caused by more Pt distributions on the gate foot edges of the high Ti/Pt/Au gate. The Pt distribution in Schottky contact metal is found to increase with the gate stem height or the gate length increasing, and thus enhancing the Schottky barrier height and expanding the gate length,which can be due to the increased internal tensile stress of Pt. The more Pt distributions for the high gate stem device also lead to more obvious Pt sinking, which reduces the distance between the gate and the In Ga As channel so that the transconductance(gm) of the high gate stem device is 70 m S/mm larger than that of the short stem device. As for the RF performances,the gate extrinsic parasitic capacitance decreases and the intrinsic transconductance increases after the gate stem height has been increased, so the RF performances of device are obviously improved. The high gate stem device yields a maximum ft of 270 GHz and fmax of 460 GHz, while the short gate stem device has a maximum ft of 240 GHz and the fmax of 370 GHz.     

单边掺杂InAlAs/InGaAs单量子阱中二维电子气的磁输运特性

研究了双子带占据的In_0.52Al_0.48As/In_0.53Ga_{0 .47}As单量子阱中磁电阻的Shubnikov-de Haas(SdH)振荡效应和霍耳效应，获得了不 同子带电子的浓度、迁移率、有效质量和能级位置.低磁感应强度(B＜1.5T)下由迁移率谱和 多载流子拟合相结合的方法得到的各子带电子浓度与通过SdH振荡得到的结果一致.在d ²ρ/dB²-1/B的快速傅里叶变换 关键词： InAlAs/InGaAs单量子阱 SdH振荡 二维电子气 磁致子带间散射     

高迁移率InGaAs/InP量子阱中的有效g因子

利用化学束外延法制备了高迁移率的In_0.53Ga_0.47As/InP量子阱样品. 在样品的低温磁输运测试中, 观察到纵向磁阻的Shubnikov-de Hass (SdH) 振荡和零场自旋分裂引起的拍频. 本文提出一种解析的方法, 即通过同时拟合不同倾斜磁场下SdH振荡的傅里叶变换谱, 得到有效g因子的大小.     

Impact of gate offset in gate recess on DC and RF performance of InAlAs/InGaAs InP-based HEMTs

A set of 100-nm gate-length InP-based high electron mobility transistors (HEMTs) were designed and fabricated with different gate offsets in gate recess. A novel technology was proposed for independent definition of gate recess and T-shaped gate by electron beam lithography. DC and RF measurement was conducted. With the gate offset varying from drain side to source side, the maximum drain current (I_ds,max) and transconductance (g_m,max) increased. In the meantime, f_T decreased while f_max increased, and the highest f_max of 1096 GHz was obtained. It can be explained by the increase of gate-source capacitance and the decrease of gate-drain capacitance and source resistance. Output conductance was also suppressed by gate offset toward source side. This provides simple and flexible device parameter selection for HEMTs of different usages.     

Strain-Compensated InGaAs/InAlAs Quantum Cascade Detector of 4.5 μm Operating at Room Temperature

We present a strain-compensated InP-based InGaAs/InAlAs photovoltaic quantum cascade detector grown by solid source molecular beam epitaxy. The detector is based on a vertical intersubband transition and electron transfer on a cascade of quantum levels which is designed to provide longitudinal optical phonon extraction stairs. By careful structure design and growth, the whole epilayer has a residual strain toward InP substrate of only -2.8× 10^-4. A clear narrow band detection spectrum centered at 4.5 μm has been observed above room temperature for a device with 200／times 200 ×μm^2 square mesa.     

InGaAs/InAlAs Five Layer Asymmetric Coupled Quantum Well (FACQW) for Ultra-Wideband Ultrafast Optical Modulators

An InGaAs/InAlAs five-layer asymmetric coupled quantum well (FACQW) is expected to show very large electrorefractive index change. n in a wideband transparency region. Band structures of the FACQW are analyzed with Luttinger-Kohn Hamiltonian. The electrorefractive characteristics of the FACQW are discussed.     

InAlAs/InGaAs/InAlAs量子阱高迁移率二维电子气系统中的反弱局域效应研究

研究了Si 重δ 掺杂In_0.52Al_0.48As/In_0.53Ga_0.47As/In_0.52Al_0.48As单量子阱内高迁移率二维电子气系统中的反弱局域效应. 研究表明，强的Rashba自旋轨道相互作用来源于量子阱高的结构反演不对称. 高迁移率系统中，粒子的运动基于弹道输运而非扩散输运. 因此，旧的理论模型不能用于拟合实验结果. 由于最新的模型在实际拟合中过于复杂，一种简单可行的近似用于处理实验结果，并获得了自旋分裂能Δ₀和自旋轨道耦合常数α两个重要的物理参数. 该结果与对纵向电阻的Shubnikov-de Haas—SdH振荡分析获得的结果一致. 高迁移率系统中的反弱局域效应研究表明，发展有效的反弱局域理论模型，对于利用Rashba自旋轨道相互作用来设计自旋器件尤为重要.     

Rashba spin-orbit coupling probed by the weak antilocalization analysis in InAlAs/InGaAs/InAlAs quantum wells as a function of quantum well asymmetry

We have investigated the values of the Rashba spin-orbit coupling constant alpha in In(0.52)Al(0.48)As/In(0.53)Ga(0.47)As/In(0.52)Al(0.48)As quantum wells using the weak antilocalization (WAL) analysis as a function of the structural inversion asymmetry (SIA) of the quantum wells. We have found that the deduced alpha values have a strong correlation with the degree of SIA of the quantum wells as predicted theoretically. The good agreement between the theoretical and experimental values of alpha suggests that our WAL approach for deducing alpha values provides a useful tool in designing future spintronics devices that utilize the Rashba spin-orbit coupling.     

Structural and Photoluminescence Properties for Highly Strain-Compensated InGaAs/InAlAs Superlattice

The effects of strain compensation are investigated by using twenty periods of highly strain-compensated InGaAs/InAlAs superlattice. The lattice mismatches of individual layers are as high as about 1%, and the thicknesses are close to critical thicknesses. X-ray diffraction measurements show that lattice imperfectness is not serious but still present, though the structural parameters are within the range of theoretical design criteria for structural stability. Rough interfaces and composition fluctuations are the primary causes for lattice imperfectness. Photoluminescence measurements show the large thermally activated nonradiative recombination in the sample. In addition, the recombination process gradually evolves from excitonic recombination at lower temperatures to band-to-band recombination at higher temperatures, which should be considered in device applications.     

100-nm T-gate InAlAs/InGaAs InP-based HEMTs with f_T = 249 GHz and f_(max) = 415 GHz

InAlAs/InGaAs high electron mobility transistors(HEMTs) on an InP substrate with well-balanced cutoff frequency fTand maximum oscillation frequency fmax are reported. An InAlAs/InGaAs HEMT with 100-nm gate length and gate width of 2 × 50 μm shows excellent DC characteristics, including full channel current of 724 mA/mm, extrinsic maximum transconductance gm.max of 1051 mS/mm, and drain–gate breakdown voltage BVDG of 5.92 V. In addition, this device exhibits fT= 249 GHz and fmax = 415 GHz. These results were obtained by fabricating an asymmetrically recessed gate and minimizing the parasitic resistances. The specific Ohmic contact resistance was reduced to 0.031 Ω·mm. Moreover,the fTobtained in this work is the highest ever reported in 100-nm gate length InAlAs/InGaAs InP-based HEMTs. The outstanding gm.max, fT, fmax, and good BVDG make the device suitable for applications in low noise amplifiers, power amplifiers, and high speed circuits.     

赝配InGaAs/InAlAs调制掺杂异质结构的Shubnikov-de Haas振荡

赝配InGaAs/InAlAs调制掺杂异质结构可以获得很高的电子气面密度和电子迁移率，从而可以制成具有优越高频和低噪声特性的高电子迁移率晶体管(HEMT).文中报道InGaAs/InAlAs调制掺杂异质结构低温下纵向和横向磁阻随磁场强度变化的Shubnikov-de Haas(SdH)振荡和量子Hall效应.对SdH振荡曲线作了快速傅里叶变换，获得了二维电子气的能带结构和各能带上的电子气面密度.分析比较了顶层InGaAs不同掺杂情况对SdH振荡的影响，结果发现顶层InGaAs重掺杂，会对表面态起屏蔽作用， 关键词：     

High-Power Microwave Photodiodes Based on MBE-Grown InAlAs/InGaAs Heterostructures

Technical Physics - The design and fabrication technology of high-power Schottky-barrier microwave mesa photodiodes from 10 to 40 μm in diameter back-illuminated through the substrate are...     

Structural investigations of InGaAs/InGaAs SLSs for optoelectronic device applications

InGaAs/InGaAs strained layer supelattices (SLSs) are interesting candidates for optoelectronic device applications working in the 1.55 μm range. However, it was recognized very early that both the miniband widths and interband transition energies in these very shallow systems are extremely sensitive to the final value of all structural parameters. As a consequence, any unwanted modification of the composition and thickness of the wells and barriers, with respect to the nominal ones, should be carefully avoided and, at the same time, systematically checked. Toward this end, since the most usefull and non-destructive techniques are X-ray and optical spectroscopy, we present in this work a comparative evaluation of their respective sensitivity.     

赝形InGaAs/InAlAs渐变异质结中的 零磁场自旋分裂

在赝形渐变ＩｎＧａＡｓ／Ｉｎ０．５２Ａｌ０．４８Ａｓ异质结的二维电子气中,发现了自旋方向向上的电子和自旋向下的电子在零磁场下存在着自旋分裂．利用ＳｈｕｂｎｉｋｏｖｄｅＨａａｓ振荡研究了异质结中的自旋分裂行为,通过振荡中的拍频现象,发现了零磁场下的自旋分裂量为８７６ｍｅＶ．