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.     

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     

高峰谷电流比的高掺杂发射区In0.53Ga0.47As/AlAs共振隧穿二极管

利用空气桥工艺设计和制作了高掺杂发射区In0.53Ga0.47As/AlAs共振隧穿二极管（RTD）。在室温下,器件的峰谷电流比大于40,峰值电流密度为24kA/cm2。建立了RTD器件等效电路模型,并从直流和微波测试结果中提取出器件参数。高峰谷电流比的RTD器件具有非常小的电容,有利于在微波/太赫兹领域中的应用。     

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”.     

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.     

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.     

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.     

InGaAs-InGaN Wafer-Bonded Current Aperture Vertical Electron Transistors (BAVETs)

In this paper, we report the fabrication process and direct-current (DC) characteristics of a wafer-bonded heterostructure-based vertical transistor. It comprises an In_0.53Ga_0.47As/In_0.52Al_0.48As/In_0.53Ga_0.47As field-effect transistor wafer-bonded to a Ga-polar In_0.1Ga_0.9N/GaN template. In the DC-bias operation of this device, the current conduction is initially confined lateral to the InGaAs channel and then flows vertically through a conductive aperture defined in the InGaN/GaN layers. The narrow aperture is isolated by ion-implanted current blocking layer (CBL) regions. The I _d–V _ds characteristics of the device demonstrate transistor-like behavior. Design optimizations have been applied to the implant and doping conditions of the InGaN/GaN layers to eliminate the leakage paths through the CBL while simultaneously obtaining unhindered current conduction through the aperture of the device.     

Ultra-thin GaxIn1−xAs/InP (0≤x≤0.47) layer growth by chemical beam epitaxy

Ga_xIn_1?xAs/InP (0≤x≤0.47) lattice-matched and compressively strained quantum wells were grown by all gas source chemical beam epitaxy (CBE). Their optical properties were investigated by photoluminescence (PL) and optical absorption measurements. The thinnest Ga_xIn_1?xAs layer was 6Å-thick (2 monolayers) for Ga_0.47In_0.53As and 3Å-thick (1 monolayer) for InAs. In PL measurements, we found that for strained materials (x<0.47) luminescence intensity dropped with decreasing barrier thickness. Optical absorption properties were measured at room temperature, and excitonic absorption peaks were clearly observed. The wavelengths of excitonic peaks were in good agreement with a theoretical estimation obtained by using an effective mass approximation including heavy and light hole energy splitting at the γ point.     

Terahertz-radiation generation in low-temperature InGaAs epitaxial films on (100) and (411) InP substrates

The spectrum and waveforms of broadband terahertz-radiation pulses generated by low-temperature In_0.53Ga_0.47As epitaxial films under femtosecond laser pumping are investigated by terahertz time-resolved spectroscopy. The In_0.53Ga_0.47As films are fabricated by molecular-beam epitaxy at a temperature of 200°C under different arsenic pressures on (100)-oriented InP substrates and, for the first time, on (411)A InP substrates. The surface morphology of the samples is studied by atomic-force microscopy and the structural quality is established by high-resolution X-ray diffraction analysis. It is found that the amplitude of terahertz radiation from the LT-InGaAs layers on the (411)A InP substrates exceeds that from similar layers formed on the (100) InP substrates by a factor of 3–5.     

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.     

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.     

Diagnostics of the hot-hole distribution function in quantum wells in a strong electric field

Modulation of the fundamental absorption edge by a high lateral electric field in a p-type In_0.21Ga_0.79As/GaAs heterostructure with quantum wells was studied at 4.2 K and electric fields as high as 1.9 kV/cm. The field-induced change in the symmetric part of the hole distribution function was measured.     

Ultrafast Dynamics of Photoexcited Charge Carriers in In<Subscript>0.53</Subscript>Ga<Subscript>0.47</Subscript>As/In<Subscript>0.52</Subscript>Al<Subscript>0.48</Subscript>As Superlattices under Femtosecond Laser Excitation

The results of experimental studies of the time dynamics of photoexcited charge carriers in In_0.53Ga_0.47As/In_0.52Al_0.48As superlattices grown by molecular-beam epitaxy on a GaAs substrate with a metamorphic buffer are reported. On the basis of the results of the numerical simulation of band diagrams, the optimal thickness of the In_0.52Al_0.48As barrier layer (4 nm) is chosen. At this thickness, the electron wave functions in In_0.53Ga_0.47As substantially overlap the In_0.52Al_0.48As barriers. This makes it possible to attain a short lifetime of photoexcited charge carriers (τ ~ 3.4 ps) at the wavelength λ = 800 nm and the pumping power 50 mW without doping of the In_0.53Ga_0.47As layer with beryllium. It is shown that an increase in the wavelength to λ = 930 nm (at the same pumping power) yields a decrease in the lifetime of photoexcited charge carriers to τ ~ 2 ps. This effect is attributed to an increase in the capture cross section of trapping states for electrons with lower energies and to a decrease in the occupancy of traps at lower excitation densities.     

Temperature dependent electron velocity-field characteristics for In0.53Ga0.47AS at high electric fields

The static electron velocity-field characteristics for n-In_0.53Gan_0.47AS have been measured at temperatures from 95 K to 300 K over a range of electric field strengths from about 10 kV/cm to beyond 100 kV/cm. The velocity decreases monotonically with increasing electric field at all temperatures over the range of field strengths investigated. The electron velocity-field curves for In_0.53Ga_0.47As exhibit a larger peak-to-valley ratio, lower high-field velocity, and a smaller high-field temperature dependence than those for GaAs measured using the same experimental technique.     

OMVPE growth of In0.53Ga0.47As on InP using tertiarybutylarsine

We have successfully grown bulk In_0.53Ga_0.47As on InP using tertiarybutylarsine (TBA), trimethylindium and trimethylgallium. The growth temperature was 602° and the V/III ratio ranged from 19 to 38. Net carrier concentrations were 2 – 4 × 10¹⁵ cm^-3, n-type, with a peak 77 K mobility of 68,000 cm²/V. sec. Increasing compensation was observed in In_0.53Ga_0.47As grown at higher V/III ratios. PL spectra taken at 5 K revealed strong near bandgap emission at 0.81 eV—with the best sample having a FWHM of 2.5 meV. At lower energies, donor-acceptor pair transitions were evident. Strong and sharp 5 K PL emission was observed from InP/In_0.53Ga_0.47As/InP quantum wells grown with TBA.     

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.     

New low contact resistance triple capping layer enabling very high Gm InAIAs/lnGaAs HEMTs

It has been demonstrated that a highly doped (Si:3 × 10¹⁹ cm^-3) triple capping layer consisting of n⁺−In_0.53Ga_0.47As, n⁺−In_0.52Al_0.48As, and n⁺-In_0.53Ga_0.47As can remarkably reduce the parasitic source resistance in InP-based high electron mobility transistors (HEMTs). The analysis of the source resistance revealed that the resistance element at the n⁺−In_0.53Ga_0.47As/un−In_0.52Al_0.48As/un-In_0.53Ga_0.47As channel heterointerfaces was as large as 70% of the source resis-tance when nonalloyed ohmic electrodes were used. The highly doped triple capping layer reduces the resistance contribution of vertical conduction between the capping layer and 2DEG channel. A low source resistance of 0.57 Ωmm and a low contact resistivity of 3 × 10⁻⁵ Ωcm² were obtained for the HEMTs with the highly doped triple capping layer, which were 60% lower and one order of magnitude smaller than those for the HEMTs with a conventional single capping layer doped 5 × 10¹⁸ cm⁻³, respectively. These values were also 70 and 30% lower than those for the HEMTs with a highly doped (3 × 10¹⁹ cm⁻³) single capping layer, respectively. The low source resistance brings high peak extrinsic transconduc-tance of 1 S/mm for a device with 0.4 μm long gate, which was 42% higher than the previously reported HEMTs with the same gate length.