Electron transport in an In<Subscript>0.52</Subscript>Al<Subscript>0.48</Subscript>As/In<Subscript>0.53</Subscript>Ga<Subscript>0.47</Subscript>As/In<Subscript>0.52</Subscript>Al<Subscript>0.48</Subscript>As quantum well with a δ-Si doped barrier in high electric fields

The electron conduction in a two-dimensional channel of an In_0.52Al_0.48As/In_0.53Ga_0.47As/In_0.52Al_0.48As quantum well (QW) with a δ-Si doped barrier has been investigated. It is shown that the introduction of thin InAs barriers into the QW reduces the electron scattering rate from the polar optical and interface phonons localized in the QW and increases the electron mobility. It is found experimentally that the saturation of the conduction current in the In_0.53Ga_0.47As channel in strong electric fields is determined by not only the sublinear field dependence of the electron drift velocity, but also by the decrease in the electron concentration n _s with an increase in the voltage across the channel. The dependence of n _s on the applied voltage is due to the ionized-donor layer located within the δ-Si doped In_0.52Al_0.48As barrier and oriented parallel to the In_0.53Ga_0.47As QW.     

High electron mobility 18300 cm2/V·s in the InAIAs/lnGaAs pseudomorphic structure obtained by channel indium composition modulation

The highest electron mobility yet reported for an InP-based pseudomorphic structure at room temperature, 18300 cm²/V·s, has been obtained by using a structure with an indium composition modulated channel, namely, In_0.53Ga_0.47As/ In_0.8Ga_0.2As/InAs/In_0.8Ga_0.2As/In_0.53Ga_0.47As. Although the total thickness of the high In-content layers (In_0.8Ga_0.2As/InAs/In_0.8Ga_0.2As) exceeds the critical thick-ness predicted by Matthews theory, In_0.8Ga_0.2As insertion makes it possible to form smooth In_0.53Ga_0.47As/In_0.8Ga_0.2As and In_0.8Ga_0.2As/InAs heterointerfaces. This structure can successfully enhance carrier confinement in the high In-content layers. This superior carrier confinement can be expected to lead to the highest yet reported electron mobility.     

Nitride-based near-ultraviolet multiple-quantum well light-emitting diodes with AlGaN barrier layers

The In_0.05Ga_0.95N/GaN, In_0.05Ga_0.95N/Al_0.1Ga_0.9N, and In_0.05Ga_0.95N/Al_0.18Ga_0.82N multiple-quantum well (MQW) light-emitting diodes (LEDs) were prepared by metal-organic chemical-vapor deposition. (MOCVD). It was found that the 20-mA electroluminescence (EL) intensity of the InGaN/Al_0.1Ga_0.9N MQW LED was two times larger than that of the InGaN/GaN MQW LED. The larger maximum-output intensity and the fact that maximum-output intensity occurred at a larger injection current suggest that Al_0.1Ga_0.9N-barrier layers can provide a better carrier confinement and effectively reduce leakage current. In contrast, the EL intensity of the InGaN/Al_0.18Ga_0.82N MQW LED was smaller because of the relaxation that occurred in the MQW active region of the sample.     

Tertiarybutylarsine and tertiarybutylphosphine for the MOCVD growth of low threshold 1.55 μm InxGa1-xAs/InP quantum-well lasers

Tertiarybutylarsine (TBA) and teriarybutylphosphine (TBP) are liquid organometallic sources that are a safer alternative to arsine and phosphine. In this work, we have grown high-quality In_0.53Ga_0.47As/InP quantum wells at a temperature of 590° with TBA and TBP partial pressures of 0.4 and 2.5 Torr, respectively. A low-temperature photoluminescence study indicated optimized column V growth interruption times of 0.5 s for In_0.53Ga_0.47As wells with InP barriers. Using the optimized growth conditions, we have obtained lattice matched In_0.53Ga_0.47As/In_xGa_1-xAs_yP_1-x single quantum-well lasers emitting at 1.55 μm. Broad-area devices with a length of 3.5 mm exhibit a low threshold current density of 220A/cm². Broad-area lasers containing four quantum wells had a threshold current density of 300A/cm² for a 3.0 mm cavity length and CW powers of 40 mW per facet for an as-cleaved 4 × 750 μm device.     

Electrical study of sulfur passivated In0.53Ga0.47As MOS capacitor and transistor with ALD Al2O3 as gate insulator

In this paper we compare the interface trap distributions D_it(E) of sulfur treated Al₂O₃/In_0.53Ga_0.47As interfaces, which underwent MOS capacitor and transistor fabrication processes. Lower interface trap densities were found close to the conduction band edge for both cases. The inversion channel MOSFET achieves high device performance despite the fact that its oxide-semiconductor interface quality is a notch below that of the MOS capacitor with optimized process.     

X-ray diffraction analysis and scanning micro-Raman spectroscopy of structural irregularities and strains deep inside the multilayered InGaN/GaN heterostructure

High-resolution X-ray diffraction analysis and scanning confocal Raman spectroscopy are used to study the spatial distribution of strains in the In _x Ga_{1 − x} N/GaN layers and structural quality of these layers in a multilayered light-emitting diode structure produced by metal-organic chemical vapor deposition onto (0001)-oriented sapphire substrates. It is shown that elastic strains almost completely relax at the heterointerface between the thick GaN buffer layer and In _x Ga_{1 − x} N/GaN buffer superlattice. It is established that the GaN layers in the superlattice are in a stretched state, whereas the alloy layers are in a compressed state. In magnitude, the stretching strains in the GaN layers are lower than the compressive strains in the InGaN layers. It is shown that, as compared to the buffer layers, the layers of the superlattice contain a smaller number of dislocations and the distribution of dislocations is more randomly disordered. In micro-Raman studies on scanning through the thickness of the multilayered structure, direct evidence is obtained for the asymmetric gradient distributions of strains and crystal imperfections of the epitaxial nitride layers along the direction of growth. It is shown that the emission intensity of the In _x Ga_{1 − x} N quantum well is considerably (more than 30 times) higher than the emission intensity of the GaN barrier layers, suggesting the high efficiency of trapping of charge carriers by the quantum well.     

p-i-n InP/InGaAs光电探测器电流及电容特性研究

为了实现高灵敏度探测,红外探测器需要得到优化。利用Silvaco器件仿真工具研究了p-i-n型InP/In_0.53Ga_0.47As/In_0.53Ga_0.47As光电探测器结构,模拟了结构中吸收层浓度和台阶宽度对暗电流及结电容的影响。结果表明,随着吸收层掺杂浓度的逐渐增大,器件暗电流逐渐减小,结电容逐渐增大;当台阶宽度变窄时,器件暗电流随之减小,结电容也随之变小。最后研究了光强和频率对器件结电容的影响：在低光强下,器件结电容基本不变;当光强增大到1 W/cm²时,器件结电容迅速增大;器件结电容随频率的升高而减小,其峰值由缺陷能级引起。     

p-i-n InP/InGaAs光电探测器的电流及电容特性研究

为了实现高灵敏度探测,红外探测器需要得到优化。利用Silvaco器件仿真工具研究了p--i--n型InP/In0.53Ga0.47As/In0.53Ga0.47As光电探测器的结构,并模拟了该结构中吸收层浓度和台阶宽度对暗电流以及结电容的影响。结果表明,随着吸收层掺杂浓度的逐渐增大,器件的暗电流逐渐减小,结电容逐渐增大。当台阶宽度变窄时,器件的暗电流随之减小,结电容也随之变小。最后研究了光强和频率对器件结电容的影响。在低光强下,器件的结电容基本不变;当光强增大到1 W/cm2时,器件的结电容迅速增大。器件的结电容随频率的升高而减小,其峰值由缺陷能级引起。     

Dry etching characteristics of In1-x-y Ga x Al y as alloys in CCl2F2:Ar and CH4:H2:Ar discharges

The etching characteristics of InGaAlAs alloys lattice-matched to InP were investigated using low pressure (1 mTorr) electron cyclotron resonance CH₄:H₂:Ar or CCl₂F₂:Ar discharges with additional radiofrequency biasing of the samples. Using CCl₂F₂:Ar discharges with ≥250V negative bias it is possible to obtain equi-rate etching of the material for all compositions between In_0.53Ga_0.47As and In_0.52Al_0.48As. At lower bias values, formation of A1F₃ on the surface leads to an inhibition of the etch rates. By making use of the differential etch rates of InGaAlAs layers of different compositions in CH₄:H₂:Ar mixtures, it is possible to choose dc bias values that allow one to stop the etching at a pre-selected depth in a multi-layer structure. For example, for -150 V bias, one can etch through In_0.53Ga_0.47As, In_0.53Ga_0.40Al_0.07As and Ino.53Ga_0.30Al_0.17As layers, and stop at an underlying layer with composition In_0.53Ga_0.20Al_0.27As.     

GaAsSb/InGaAs tunnel field effect transistor with a pocket layer

This work proposes a new GaAs_0.51Sb_0.49/In_0.53Ga_0.47As heterojunction tunnel field effect transistor (HTFET) with a 6-nm In_0.7Ga_0.3As layer (pocket) between the source and channel. Compared with InGaAs homojunction TFETs, the proposed HTFET has a steeper subthreshold swing at a higher drain current, owing to its lower source-to-channel tunnel barrier height. It has a maximum on-state current of 11.98 μA/μm at room temperature, which is more than ten times the on-state current obtained from an InGaAs homojunction TFET.     

Enhancement-mode In0.53Ga0.47As metal-oxide-semiconductor field-effect transistors with sol–gel processed gate dielectrics

Enhancement-mode In_0.53Ga_0.47As n-type metal-oxide-semiconductor field-effect transistors (MOSFETs), with barium zirconate titanate (BZT) and titanium dioxide (TiO₂) high-κ materials prepared via the solution–gelation process as gate dielectrics, have been fabricated. The dielectric constants of BZT and TiO₂ are 6.67 and 19.3, respectively. The In_0.53Ga_0.47As MOSFET with TiO₂ exhibits better electrical characteristics than the In_0.53Ga_0.47As MOSFET with BZT. These characteristics include higher maximum drain current density, higher maximum transconductance, and smaller subthreshold swing.     

Comparative assessment of InGaAs sub-channel and InAs composite channel double gate (DG)-HEMT for sub-millimeter wave applications

This work analyses the impact of channel material, channel thickness (T_CH) and gate length (L_g) on the various performance device metrics of Double-gate (DG) High Electron Mobility Transistor (HEMT) by using 2D Sentaurus TCAD simulation. A comparison between In_0.53Ga_0.47As/In_0.7Ga_0.3As/In_0.53Ga_0.47As sub-channel and In_0.7Ga_0.3As/InAs/In_0.7Ga_0.3As composite channel DG-HEMT along with SG-HEMT is made by characterizing the device with structural and geometrical parameters suitable for applications requiring high frequency operations. The DG-In_0.53Ga_0.7As/In_0.7Ga_0.3As/In_0.53Ga_0.7As sub-channel/DG-In_0.7Ga_0.3As/InAs/In_0.7Ga_0.3As composite channel HEMT with channel thickness of 13 nm and barrier thickness (T_B) of 2 nm with L_g = 30 nm are seen offering a positive threshold voltage (V_T) of 0.298/0.21 V, transconductance (g_m) of 3.09/3.3 mS/µm, with cut-off frequency (f_T) and maximum oscillation frequency (f_max) of 776/788 GHz and 905/978 GHz, respectively at V_ds = 0.5 V is obtained. If the channel thickness of the DG-InAs composite channel device is scaled and reduced to 10 nm, the RF performances are further enhanced to 809 GHz (f_T) and 1030 GHz (f_max). Compared to DG-InGaAs sub-channel device, the device with thin DG-InAs composite channel device shows a better performance in terms of drain current (I_ds), analog/RF performance thereby making it preferable for future THz applications.     

Monte Carlo simulations of InGaAs nano-MOSFETs

The potential performance of sub-50 nm n-type implant free III-V MOSFETs with an In_0.75Ga_0.25As channel is studied using Monte Carlo (MC) device simulations. The simulated I_D-V_G characteristics of the In_0.75Ga_0.25As implant free MOSFETs are compared with equivalent In_0.3Ga_0.7As implant free MOSFETs and with a state-of-the-art silicon CMOS transistors. The study is based on careful calibration of the MC simulator against experimental data obtained from a δ-doped In_0.52Ga_0.48As/ In_0.53Ga_0.47As/In_0.75Ga_0.25As heterostructure with a high-κ gate dielectric. At 0.8 V supply voltage, the 30 nm gate length In_0.75Ga_0.25As implant free III-V MOSFET delivers a drive current of 1730 μA/μm as compared to the 1550 μA/μm obtained in the equivalent In_0.3Ga_0.7As implant free MOSFET. When this high indium channel transistor is scaled to 20 and 15 nm gate lengths the drive current at 0.8 V supply voltage increases to 2465 and 2745 μA/μm, respectively, making it a good candidate for high performance, low power digital applications at the 22 nm technology generation and beyond.     

光谱响应范围为0.7-1.65μm的一种近红外光阴极

(一)前言 众所周知,夜视仪器最基本的要求是看得远、看得清。夜视仪器中主要的部件除光学透镜外就是微光管。而光阴极则是微光管的“眼睛”。目前,二、三代微光管中的光阴极分别为Sb-K-Na-Cs与GaAs,它们的长波阈约为0.9μm。夜天空辐射强度是满月与星空交替变化的。满月以可见光辐射为主,而星空则以近红外辐射为主。在星空辐射下,波长大于1μm的辐射强度比可见光的辐射强度约大1—2个数量级。因此,Sb-K-Na-Cs与GaAs两种光阴极用于微光管内接收夜天空辐射,对满月是可以的,但是对波长长于0.9μm     

Very high purity In0.53Ga0.47As grown by molecular beam epitaxy

Very high purity In0_0.53Ga_0.47As layers were grown by molecular beam epitaxy (MBE). Origins ofn-type impurities in undoped In_0.53Ga_0.47As grown on an InP:Fe substrate were systematically examined. The most possible origins were impurities diffusing from the InP:Fe substrate and those contained in As molecular beam. These impurities were dramatically reduced by using an InAlAs buffer layer and a growth condition of high substrate temperature and low As pressure. The lowest electron concentration of the In0_0.53Ga_0.47As layer wasn = 1.8 × 10¹³ cm_-3 with mobilitiesμ = 15200 cm²/Vs at 300 K andμ = 104000 cm²/Vs at 77 K.     

Femtosecond optical response of low temperature grown In0.53Ga0.47As

A femtosecond, tunable color center laser was used to conduct degenerate pump-probe transmission spectroscopy of thin film low temperature grown molecular beam epitaxy In_0.53Ga_0.47As samples. Low temperature molecular beam epitaxy In_0.53Ga_0.47As exhibits a growth-temperature dependent femtosecond optical response when probed near the conduction band edge. Below T_g=250°C, the optical response time of the material is subpicosecond in duration, and we observed induced absorption, which we suggest is due to the formation of a quasi-“three-level system”.     

20-nm enhancement-mode metamorphic GaAs HEMT with highly doped InGaAs source/drain regions for high-frequency applications

In this article, the DC and RF performance of a SiN passivated 20-nm gate length metamorphic high electron mobility transistor (MHEMT) on GaAs substrate with highly doped InGaAs source/drain (S/D) regions have investigated using the Synopsys TCAD tool. The 20-nm enhancement-mode (E-mode) MHEMT device also features δ-doped sheets on either side of the In_0.53Ga_0.47As/InAs/In_0.53Ga_0.47As channel which exhibits a transconductance of 3100 mS/mm, cut-off frequency (f_T) of 740 GHz and a maximum oscillation frequency (f_max) of 1040 GHz. The threshold voltage of the device is found to be 0.07 V. The room temperature Hall mobilities of the 2-dimensional sheet charge density are measured to be over 12,600 cm²/Vs with a sheet charge density larger than 3.6 × 10¹² cm^?2. These high-performance E-mode MHEMTs are attractive candidates for sub-millimetre wave applications such as high-resolution radars for space research, remote atmospheric sensing, imaging systems and also for low noise wide bandwidth amplifier for future communication systems.     

Selective area LPE growth and open tube diffusion in InGaAs/InP

Techniques are described in which selective chemical etching, localised LPE growth and localised diffusion in In_0.53Ga_0.47As and InP were carried out. Spun-on silica films were employed as masks in these processes and its performance was found to be comparable with pyrolytic or rf deposited films. Localised LPE growth of In_0.53Ga_0.47As and in-situ etching enabled well-controlled islands of In_0.53Ga_0.47As embedded in InP to be produced. Orientation dependent growth rates were also identified. An open-tube diffusion technique based on an LPE growth system has been successfully used for diffusion of Zn into InP and In_0.53 Ga_0.47As from Sn solutions. A strong variation of diffusion depth in InP with Zn concentration in Sn has been observed at low Zn concentrations but a constant depth is approached for Zn concentrations greater than ∼0.08 atomic fraction.     

Simulation of InGaAs subchannel DG-HEMTs for analogue/RF applications

The paper reports on the influence of a barrier thickness and gate length on the various device parameters of double gate high electron mobility transistors (DG-HEMTs). The DC and RF performance of the device have been studied by varying the barrier thickness from 1 to 5 nm and gate length from 10 to 150 nm, respectively. As the gate length is reduced below 50 nm regime, the barrier thickness plays an important role in device performance. Scaling the gate length leads to higher transconductance and high frequency operations with the expense of poor short channel effects. The authors claim that the 30-nm gate length, mole fractions tuned In_0.53Ga_0.47As/In_0.7Ga_0.3As/In_0.53Ga_0.47As subchannel DG-HEMT with optimised device structure of 2 nm In_0.48Al_0.52As barrier layer show a peak g_m of 3.09 mS/µm, V_T of 0.29 V, I_ON/I_OFF ratio of 2.24 × 10⁵, subthreshold slope ~73 mV/decade and drain induced barrier lowering ~68 mV/V with f_T and f_max of 776 and 905 GHz at V_ds = 0.5 V is achieved. These superior performances are achieved by using double-gate architecture with reduced gate to channel distance.     

Study of dual-blue light-emitting diodes with asymmetric AlGaN graded barriers

A dual-blue light-emitting diode （LED） with asymmetric A1GaN composition-graded barriers but without an AlGaN electron blocking layer （EBL） is analyzed numerically. Its spectral stability and efficiency droop are improved compared with those of the conventional InGaN/GaN quantum well （QW） dual-blue LEDs based on stacking structure of two In0.18Ga0.szN/GaN QWs and two In0.12Ga0.88N/GaN QWs on the same sapphire substrate. The improvement can be attributed to the markedly enhanced injection of holes into the dual-blue active regions and effective reduction of leakage current.