Super-flat interfaces in In0.53Ga0.47As/In0.52Al0.48As quantum wells grown on (411)A InP substrates by molecular beam epitaxy

Effectively atomically flat interfaces over a macroscopic area (“(411)A super-flat interfaces”) were successfully achieved in In_0.53Ga_0.47As/In_0.52Al_0.48As quantum wells (QWs) grown on (411)A InP substrates by molecular beam epitaxy (MBE) at a substrate temperature of 570°C and V/III=6. Surface morphology of the In_0.53Ga_0.47As/In_0.52Al_0.48As QWs was smooth and featureless, while a rough surface of those simultaneously grown on a (100) InP substrate was observed. Photoluminescence (PL) linewidths at 4.2 K from the (411)A QWs with well width of 0.6–12 nm were 20–30 % narrower than those grown on a (100) InP substrate and also they are almost as narrow as each of split PL peaks for those of growth-interrupted QWs on a (100) InP substrate. In the case of the (411)A QWs, only one PL peak with very narrow linewidth was observed from each QW over a large distance (7 mm) on a wafer.     

In0.48Ga0.52P/In0.20Ga0.80As/GaAs pseudomorphic high electron mobility transistors grown by solid-source molecular-beam epitaxy using a valved phosphorus cracker cell

In_0.48Ga_0.52P/In_0.20Ga_0.80As/GaAs pseudomorphic high electron mobility transistor (p-HEMT) structures were grown by solid-source molecular beam epitaxy (SSMBE) using a valved phosphorus cracker cell. The sheet carrier density at room temperature was 3.3 × 10¹²cm^?2. A peak transconductance (G _m) of 267 mS mm^?1 and peak drain current density (I _ds) of 360 mA mm^?1 were measured for a p-HEMT device with 1.25 µm gate length. A high gate-drain breakdown voltage (BV _gd) of 33V was measured. This value is more than doubled compared with that of a conventional Al_0.30Ga_0.70As/In_0.20Ga_0.80As/GaAs device. The drain-source breakdown voltage (BV _ds) was 12.5V. Devices with a mushroom gate of 0.25 µm gate length and 80 µm gate width achieved a peak transconductance (G _m) of 420 mS mm^?1 and drain current density of nearly 500mA mm^?1. A high cutoff frequency (f _T) of 58GHz and maximum oscillation frequency (f _max) of 120 GHz were obtained. The results showed that the In_0.48Ga_0.52P/In_0.20Ga_0.80As/GaAs material system grown by SSMBE using the valved phosphorus cracker cell for the In^0.48Ga^0.52P Schottky and spacer layers is a viable technology for high frequency p-HEMT device applications.     

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.     

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.     

Thermal characteristics of InP, InAlAs, and AlGaAsSb metamorphic buffer layers used in In0.52Al0.48As/In0.53Ga0.47As heterojunction bipolar transistors grown on GaAs substrates

In_0.52Al_0.48As/In_0.53Ga_0.47As heterojunction bipolar transistors (HBTs) were grown metamorphically on GaAs substrates by molecular beam epitaxy. In these growths, InAlAs, AlGaAsSb, and InP metamorphic buffer layers were investigated. The InAlAs and AlGaAsSb buffer layers had linear compositional grading while the InP buffer layer used direct binary deposition. The transistors grown on these three layers showed similar characteristics. Bulk thermal conductivities of 10.5, 8.4, and 16.1 W/m K were measured for the InAlAs, AlGaAsSb, and InP buffer layers, as compared to the 69 W/m K bulk thermal conductivity of bulk InP. Calculations of the resulting HBT junction temperature strongly suggest that InP metamorphic buffer layers should be employed for metamorphic HBTs operating at high power densities.     

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.     

Persistent photoconductivity and electron mobility in In0.52Al0.48As/In0.53Ga0.47As/In0.52Al0.48As/InP quantum-well structures

The influence of the width of the quantum well L and doping on the band structure, scattering, and electron mobility in nanoheterostructures with an isomorphic In_0.52Al_0.48As/In_0.53Ga_0.47As/In_0.52Al_0.48As quantum well grown on an InP substrate are investigated. The quantum and transport mobilities of electrons in the dimensionally quantized subbands are determined using Shubnikov-de Haas effect measurements. These mobilities are also calculated for the case of ionized-impurity scattering taking into account intersub-band electron transitions. It is shown that ionized-impurity scattering is the dominant mechanism of electron scattering. At temperatures T < 170 K, persistent photoconductivity is observed, which is explained by the spatial separation of photoexcited charge carriers.     

长波阈为1.65μm的透射式负电子亲和势光阴极组成结构的设计

透射式负电子亲和势GaAs光阴极已应用于成像器件。由于GaAs的禁带宽度为1.42eV,长波阈约为0.9μm。因此透射式负电子亲和势GaAs光阴极的工作波长范围为0.4—0.9μm。迄今尚未见报道长波阈大于1μm的透射式负电子亲和势Ⅲ-Ⅴ族化合物光     

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.     

Analysis of temperature coefficients for III–V multi‐junction concentrator cells

The temperature dependence of the I–V parameters of different III–V multi‐junction concentrator cells at several concentration levels was investigated. Moreover, the influence of spectral changes on the temperature coefficients of multi‐junction solar cells was examined. Complete sets of temperature coefficients of a metamorphic Ga_0.35In_0.65P/Ga_0.83In_0.17As dual‐junction cell, a metamorphic Ga_0.35In_0.65P/Ga_0.83In_0.17As/Ge triple‐junction cell and a lattice‐matched Ga_0.50In_0.50P/Ga_0.99In_0.01As/Ge triple‐junction cell determined under well‐controlled laboratory conditions are reported. Copyright © 2012 John Wiley & Sons, Ltd.     

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.     

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.     

Effect of thin strain-compensated Al0.6Ga0.4P layers on the growth of multiple-stacked InP/In0.5Al0.3Ga0.2P quantum dots

Multiple-stacked InP self-assembled quantum dots (SAQD or QD) were grown on an In_0.5Al_0.3Ga_0.2P matrix lattice-matched on a GaAs (001) substrate using metalorganic chemical vapor deposition. Cathodoluminescence (CL) scanning electron microscopy, and transmission electron microscopy were employed to characterize the optical, morphological, and structural properties of the grown QDs. We found that the CL line width broadens and the surface becomes rough with an increase in the number of stacked QD layers in the structure. However, by introducing thin tensile-strained Al_0.6Ga_0.4P layers in the middle of In_0.5Al_0.3Ga_0.2P spacer layers to compensate the compressive strain of the InP QD layers, the CL and morphology are significantly improved. Using this technique, 30-stacked InP/In_0.5Al_0.3Ga_0.2P QD structures with improved CL properties and surface morphology were realized.     

Impurity-free intermixing in compressively strained InGaAsP multiple quantum well structures

We report on controlled band gap modification in a compressively strained InGaAsP multi-quantum well-laser structure using different encapsulating layers followed by rapid thermal processing (RTP). The structure used was designed as a 1.55 μm laser with an active region consisting of three In_0.76Ga_0.24As_0.85P_0.15 quantum wells with In_0.76Ga_0.24As_0.52P_0.48 barriers grown by metal organic chemical vapor deposition. The heterostructure is capped with 100 nm thick InGaAs layer. Prior to RTP, the samples were coated with various dielectric layers or a thin film of low temperature (300°C) grown InP. Using a Si_xN_y film deposited by plasma-enhanced chemical vapor deposition with a refractive index of about 2.0, quantum well intermixing (QWI) was effectively suppressed. The suppression effect was independent of the Si_xN_y film thickness for layers of 30–2400 nm. With an e-beam-evaporated SiO₂ film, QWI was enhanced and a net blue shift of about 100 nm can be achieved between the samples covered with SiO₂ and Si_xN_y after RTP at 750°C for 100 s. Furthermore, InP grown at a low temperature by gas-source molecular beam epitaxy was proved to be even more efficient in enhancing QWI. Group V interstitial diffusion is used to explain the enhanced QWI between the wells and adjacent barriers which have the same group III compositions. Two-section tunable laser operated around 1.55 μm based on this laser structure was fabricated using this technique.     

Novel In0.52Al0.48As/In0.53Ga0.47As metamorphic high electron mobility transistors on GaAs substrate with InxGa1−xP graded buffer layers

Compositionally graded In_xGa_1−xP (x=0.48→x=1) metamorphic layers have been grown on GaAs substrate by solid source molecular beam epitaxy using a valved phosphorus cracker cell. Three series of samples were grown to optimize the growth temperature, V/III ratio and grading rate of the buffer layer. X-ray diffraction (XRD) and photoluminescence (PL) were used to characterize the samples. The following results have been obtained: (1) XRD measurement shows that all the samples are nearly fully strain relaxed and the strain relaxation ratio is about 96%; (2) the full-width at half-maximum (FWHM) of the XRD peak shows that the sample grown at 480°C offers better material quality; (3) the grading rate does not influence the FWHM of XRD and PL results; (4) adjustment of the V/III ratio from 10 to 20 improves the FWHM of XRD peak, and the linewidth of PL peak is close to the data obtained for the lattice-matched sample on InP substrate. The optimization of growth conditions will benefit the metamorphic HEMTs grown on GaAs using graded InGaP as buffer layers.     

Process characterization and evaluation of hydride VPE grown Ga x In1−x As using a Ga/In alloy source

A novel, simplified hydride vapor phase epitaxy (VPE) method based on the utilization of Ga/In alloys as the group III source was studied for deposition of Ga_xIn_1-xAs. The effects of a wide range of experimental variables (i.e., inlet mole fractions of HC1 and AsH₃, deposition temperature, gas velocity, Ga/ln alloy composition, and reactor geometry) on the ternary composition and growth rate were investigated. The growth rate of Ga _x In₁₋ xAs was found to increase with increasing deposition temperature and exhibited a maximum with inlet HC1 mole fraction. The growth rate increases slightly with inlet AsH₃ mole fraction and is independent of gas velocity. The Ga composition of the deposited film increased with increasing inlet HC1 mole fraction and gas velocity. Increased In concentrations were observed with increases in inlet AsH₃ mole fraction and deposition temperatures. Layers of Ga_0.47In_0.53As lattice matched to InP were successfully grown from alloys containing 5 to 8 at.% Ga. These layers were used to produce state-of-the-artp- i- n photodetectors having the following characteristics: dark current,I _d(- 5 V) = 10-20 nA; responsivity,R = 0.84-0.86 A/W; capacitance,C = 0.88–0.92 pF; breakdown voltage,V _b > 40 V. This study demonstrated for the first time that a simplified hydride VPE process with a Ga/ln alloy source is capable of producing device quality epitaxial layers.     

A comparative study of electrical and optical properties of InN and In0.48Ga0.52N

We present results of our studies concerning electrical and optical properties of In_0.48Ga_0.52N and InN. Hall measurement were carried out at temperatures between T=77 and 300 K. Photoluminescence (PL) spectrum in InN and In_0.48Ga_0.52N. InN has a single peak at 0.77 eV at 300 K. However, the PL in In_0.48Ga_0.52N has two peaks; a prominent peak at 1.16 eV and a smaller peak at 1.55 eV. These two peaks are attributed to Indium segregation corresponding to a high Indium concentration of 48% and a low concentration of 36%. High electric field measurements indicate that drift velocity that tends to saturate at around V_d=1.0×10⁷ cm/s at 77 K in InN at an electric field of F=12 kV/cm. However, in In_0.48Ga_0.52N the I–V curve is almost linear up to an electric field of F=45 kV/cm, where the drift velocity is V_d=1.39×10⁶ cm/s. At applied electric fields above this value a S-type negative differential resistance (NDR) is observed leading to an instability in the current and to the irreversible destruction of the sample.     

120nm栅长In0.7Ga0.3As/In0.52Al0.48As HEMTs 器件

利用新型的PMMA/PMGI/ZEP520/PMGI四层胶T形栅电子束光刻技术制备出120nm栅长InP基雁配In0.7Ga0.3As/In0.52Al0.48As 高电子迁移率晶体管。制作出的InP基HEMT器件获得了良好的直流和高频性能,跨导、饱和漏电流密度、阈值电压、电流增益截止频率和最大单向功率增益频率分别达到520 mS/mm, 446 mA/mm, -1.0 V, 141 GHz 及 120 GHz。文中的材料结构和所有器件制备均为本研究小组自主研究开发。     

Radiation resistance of MBE-grown GaInP/GaAs-based solar cells

Proton irradiation-based degradation characteristics for molecular beam epitaxy (MBE) grown Ga_0·51In_0·49P/GaAs single-junction tandem solar cells of n/p configuration are reported. The cells were irradiated with 3-MeV protons up to fluences of 10¹³ cm⁻². The cells were characterized with current–voltage (I–V) measurements at AMO conditions, and with spectral measurements. The damage coefficient for the GaAs cells was calculated using numerical modelling by the PC-1D program, and the result was compared with the InP damage coefficient. By using the ‘displacement damage dose’ approach, the degradation characteristics were compared with the published data for InP and GaAs/Ge solar cells. In addition, these MBE results were compared with the radiation behavior of metal-organic chemical vapor deposition (MOCVD)-grown Ga_0·51In_0·49P/GaAs single-, and double-junction solar cells of p/n configuration. © 1998 John Wiley & Sons, Ltd.     

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.