Electrical behavior of modulation-and delta-doped Al x Ga1 − x As/In y Ga1 − y As/GaAs PHEMT structures

Modulation-and delta-doped Al_xGa_{1 ? x} As/In_yGa_{1 ? y} As/GaAs PHEMT structures are grown by MBE. The effect is examined of changes in the technique and level of doping on the electrical behavior of the structures. Photoluminescence spectroscopy combined with Hall-effect measurements is shown to be an effective strategy for the purpose. The experimental results are interpreted on the basis of calculated conductionband diagrams.     

Interfacial Reactions in Cu/Ga and Cu/Ga/Cu Couples

Cu-to-Cu bonding to connect through-silicon vias in three-dimensional integrated-circuit packaging is the most important interconnection technology in the next-generation semiconductor industry. Soldering is an economic and fast process in comparison with diffusion bonding methods. Ga has high solubility of up to 20 at.% in the Cu-rich face-centered cubic (FCC) phase and high mobility at moderate temperatures. In this work, an attempt has been made to evaluate Ga-based Cu-to-Cu interconnection by transient liquid-phase (TLP) bonding. The Cu/Ga interfacial reactions at temperatures ranging from 160°C to 300°C were examined. For reactions at temperatures lower than 240°C, the reaction path is Cu/γ ₃-Cu₉Ga₄/θ-CuGa₂/liquid, where the γ ₃-Cu₉Ga₄ and θ-CuGa₂ phases are thin planar and thick scalloped layers, respectively, while for the reactions at 280°C and 300°C, the scalloped γ ₃-Cu₉Ga₄ phase is the only reaction product. The phase transformation kinetics, reaction mechanisms, and microstructural evolution in the Cu/Ga couples are elaborated. In addition, reactions of Cu/Ga/Cu sandwich couples at 160°C were investigated. The original Cu/liquid/Cu couples isothermally transformed to Cu/γ ₃-Cu₉Ga₄/ θ-CuGa₂/γ ₃-Cu₉Ga₄/Cu couples as the reaction progressed. However, cracks were observed in the θ-CuGa₂ phase regions after metallographic processing. The brittle θ-CuGa₂ phase is undesirable for Ga-based TLP bonding.     

GaAs／AlxGa1—xAs和AlxGa1—xAs／AlAs超晶格的喇曼散射对比研究

报道不同层厚的ＡｌＡｓ／ＡｌｘＧａ１－ｘＡｓ及ＧａＡｓ／ＡｌｘＧａ１－ｘＡｓ短周期超晶格的纵光学声子模的室温喇曼散射测量结果．在非共振条件下,观察到ＡｌＡｓ／ＡｌｘＧａ１－ｘＡｓ中限制在ＡｌｘＧａ１－ｘＡｓ混晶层中的类ＧａＡｓＬＯ限制模和限制在ＡｌＡｓ层中的ＡｌＡｓＬＯ限制模,还观察到ＧａＡｓ／ＡｌｘＧａ１－ｘＡｓ中限制在ＡｌｘＧａ１－ｘＡｓ混晶层中的类ＡｌＡｓＬＯ限制模和限制在ＧａＡｓ层中的ＧａＡｓＬＯ限制模．在近共振条件下,还观察到了ＡｌＡｓ／ＡｌｘＧａ１－ｘＡｓ中ＡｌＡｓ的界面模．根据线性链模型,把测量的ＬＯ限制模的频率按照ｑ＝ｍｎ＋１２πα０展开,给出了ＡｌｘＧａ１－ｘＡｓ混晶的类ＡｌＡｓ支和类ＧａＡｓ支光学声子色散曲线．     

退火后无应变Ga1-xInxNyAs1-y/GaAs量子阱的带隙

针对快速热退火引起的N最近邻原子环境的变化,建立了热平衡态下Ga1-xInxNyAs1-y合金中各二元化合键的统计分布模型.并将理论计算得到的N周围平均In原子数r引入到BAC经验模型中,对退火后的Ga1-xInxNyAs1-y体材料带隙进行了计算.最后,利用讨论BAC模型中电子波函数边界条件的方法,计算了无应变Ga1-xInxNyAs1-y/GaAs量子阱的带隙.     

退火后无应变Ga1-xInxNyAs-y/GaAs量子阱的带隙

针对快速热退火引起的N最近邻原子环境的变化,建立了热平衡态下Ga1-xInxNyAs-y合金中各二元化合键的统计分布模型.并将理论计算得到的N周围平均In原子数r引入到BAC经验模型中,对退火后的Ga1-xInxNyAs-y体材料带隙进行了计算.最后,利用讨论BAC模型中电子波函数边界条件的方法,计算了无应变Ga1-xInxNyAs-y/GaAs量子阱的带隙.     

A novel InGaP/Al/sub x/Ga/sub 1-x/As/GaAs CEHBT

A new and interesting InGaP/Al/sub x/Ga/sub 1-x/As/GaAs composite-emitter heterojunction bipolar transistor (CEHBT) is fabricated and studied. Based on the insertion of a compositionally linear graded Al/sub x/Ga/sub 1-x/As layer, a near-continuous conduction band structure between the InGaP emitter and the GaAs base is developed. Simulation results reveal that a potential spike at the emitter/base heterointerface is completely eliminated. Experimental results show that the CEHBT exhibits good dc performances with dc current gain of 280 and greater than unity at collector current densities of J/sub C/=21kA/cm/sup 2/ and 2.70/spl times/10/sup -5/ A/cm/sup 2/, respectively. A small collector/emitter offset voltage /spl Delta/V/sub CE/ of 80 meV is also obtained. The studied CEHBT exhibits transistor action under an extremely low collector current density (2.7/spl times/10/sup -5/ A/cm/sup 2/) and useful current gains over nine decades of magnitude of collector current density. In microwave characteristics, the unity current gain cutoff frequency f/sub T/=43.2GHz and the maximum oscillation frequency f/sub max/=35.1GHz are achieved for a 3/spl times/20 /spl mu/m/sup 2/ device. Consequently, the studied device shows promise for low supply voltage and low-power circuit applications.     

Millimeter and submillimeter detection using Ga1−xAlxAs/GaAs heterostructures

We have shown that a Ga_1?xAl_xAs/GaAs heterostructure can be used as a sensitive tunable detector of mm-wave/sub-mm-wave radiation. The mechanism for detection requires the application of a magnetic field varying from approximately 0.2T at 94GHz (3.2mm wavelength) to 6.2T at 2500GHz (119μm wavelength). The responsivity and N.E.P. at 3.2mm have been roughly estimated at 200V/W and 5×10^?11W/?Hz respectively. The speed of such a detector could be several orders of magnitude greater than comparable InSb detectors.     

High-gain wide-gap-emitter Ga1-xAlxAs-GaAs phototransistor

A Ga1-xAlxAs-GaAs heterostructure phototransistor has been manufactured and tested. The device is an n-p-n structure employing the `wide-gap-emitter? effect. High internal current gain (>2000) has been achieved.     

Ultralow leakage In/sub 0.53/Ga/sub 0.47/As p-i-n photodetector grown on linearly graded metamorphic In/sub x/Ga/sub 1-x/P buffered GaAs substrate

A novel top-illuminated In/sub 0.53/Ga/sub 0.47/As p-i-n photodiodes (MM-PINPD) grown on GaAs substrate by using linearly graded metamorphic In/sub x/Ga/sub 1-x/P (x graded from 0.49 to 1) buffer layer is reported. The dark current, optical responsivities, noise equivalent power, and operational bandwidth of the MM-PINPD with aperture diameter of 60 /spl mu/m are 13 pA, 0.6 A/W, 3.4/spl times/10/sup -15/ W/Hz/sup 1/2/, and 7.5 GHz, respectively, at 1550 nm. The performances of the MM-PINPD on GaAs are demonstrated to be comparable to those of a similar device made on InGaAs-InP substrate.     

Highly linear Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMTs

We report an Al/sub 0.3/Ga/sub 0.7/N-Al/sub 0.05/Ga/sub 0.95/N-GaN composite-channel HEMT with enhanced linearity. By engineering the channel region, i.e., inserting a 6-nm-thick AlGaN layer with 5% Al composition in the channel region, a composite-channel HEMT was demonstrated. Transconductance and cutoff frequencies of a 1 /spl times/100 /spl mu/m HEMT are kept near their peak values throughout the low- and high-current operating levels, a desirable feature for linear power amplifiers. The composite-channel HEMT exhibits a peak transconductance of 150 mS/mm, a peak current gain cutoff frequency (f/sub T/) of 12 GHz and a peak power gain cutoff frequency (f/sub max/) of 30 GHz. For devices grown on sapphire substrate, maximum power density of 3.38 W/mm, power-added efficiency of 45% are obtained at 2 GHz. The output third-order intercept point (OIP3) is 33.2 dBm from two-tone measurement at 2 GHz.     

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.     

Double heterojunction bipolar transistor in Al/sub x/Ga/sub 1-x/As/GaAs/sub 1-y/Sb/sub y/ system

Double heterojunction bipolar transistors based on the Al/sub x/Ga/sub 1-x/As/GaAs/sub 1-y/Sb/sub y/ system are examined. The base layer consists of narrow band gap GaAs/sub 1-y/Sb/sub y/ and the emitter and collector consist of wider band gap Al/sub x/Ga/sub 1-x/As. Preliminary experimental results show that AlGaAs/GaAsSb/GaAs DHBTs exhibit a current gain of five and a maximum collector current density of 5*10/sup 4/ A/cm/sup 2/.<>     

Binding energies of shallow impurities in asymmetric strained wurtzite AlxGa1-xN/ GaN/Aly Ga1-yN quantum wells

The ground state binding energies of hydrogenic impurities in strained wurtzite AlxGa1-xN/GaN/AlyGa1-y>N quantum wells are calculated numerically by a variational method. The de-pendence of the binding energy on well width, impurity location and Al concentrations of the left and right barriers is discussed, including the effect of the built-in electric field induced by spontaneous and piezoelectric polarizations. The results show that the change in binding energy with well width is more sensitive to the impurity position and barrier heights than the barrier widths, especially in asymmetric well structures where the barrier widths and/or barrier heights differ. The binding energy as a function of the impurity position in symmetric and asymmetric structures behaves like a map of the spatial distribution of the ground state wave function of the electron. It is also found that the influence on the binding energy from the Al concentration of the left barrier is more obvious than that of the right barrier.     

Orthorhombic distortion of mismatched In X Ga1−X As/InP heterostructures

Thin, mismatched epilayers tetragonally distort to form coherent interfaces. Beyond the critical thickness, misfit dislocations relieve strain. These dislocations form in an asymmetric pattern on (001) zinc-blende substrates. We show that this results in a change of crystal symmetry from tetragonal to orthorhombic for partially relaxed, mismatched In _x Ga_1−x As epilayers in either tension or compression on InP. This distortion is detected by both double-crystal x-ray diffraction and ellipsometry. The orthorhombic symmetry must be taken into account when measuring the composition of partially-relaxed epilayers by x-ray diffraction.     

缓冲层对多量子阱材料GaAs／Ga1-xAlxAs共振态的影响

从理论上研究缓冲层的厚度和特性对多量子阱材料(GaAs／Ga1-xAlxAs)中的共振态的影响，利用界面响应理论的格林函数方法，计算了局域和总电子态密度以及电子对结的穿透率，展示了缓冲层特性对态密度特征峰、穿透率的影响。结果表明，缓冲层具有控制共振隧穿电子和影响系统电子态的作用。     

Determination of the Ga content in GaxIn1-xSb for high-speed transferred-electron devices

Fundamental properties of the transferred-electron effect of LPE grown GaxIn1-xSb have been examined. In view of the considerably low threshold field (400-600 V/cm, 0.4 < x < 0.8), with a low-saturation domain velocity (5 times 10^{6} cm/s, 0.55 < x < 0.8), and having a relatively low-impact ionization rate, GaxIn1-xSb may be one of the useful materials for high-speed logic devices. An optimum Ga composition for the device is determined to be between 0.7 and 0.8, both from the impact ionization in the high-field domain and the temperature dependence of the current peak-to-valley ratios. A power-delay product of 20 fJ, which is about 1/50 of that of GaAs Gunn logic, is expected in the Gunn-mode operation of the gigabit rate.     

Al/sub 0.3/Ga/sub 0.7/As/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) doped-channel field-effect transistors (DCFET's)

The properties of both lattice-matched and strained doped-channel field-effect transistors (DCFET's) have been investigated in AlGaAs/In/sub x/Ga/sub 1-x/As (0/spl les/x/spl les/0.25) heterostructures with various indium mole fractions. Through electrical characterization of grown layers in conjunction with the dc and microwave device characteristics, we observed that the introduction of a 150-/spl Aring/ thick strained In/sub 0.15/Ga/sub 0.85/As channel can enhance device performance, compared to the lattice-matched one. However, a degradation of device performance was observed for larger indium mole fractions, up to x=0.25, which is associated with strain relaxation in this highly strained channel. DCFET's also preserved a more reliable performance after biased-stress testings.<>     

小垂直发散角大光腔980nm单模InGaAs/GaAs/AlGaAs量子阱激光器

通过采用经过优化的新型大光腔结构,脊形波导980nm单模InGaAs/GaAs/AlGaAs多量子阱半导体激光器在保持大功率光输出的同时获得了较小的垂直发散角.结果表明波导中的光功率密度可以降低,获得了大于400mW、斜率效率0.89W/A的输出光功率,垂直方向远场发散角也降低到23°.     

Very-low-threshold, strained In/sub y/Ga/sub 1-y/As-GaAs quantum-well lasers defined by impurity-induced disordering

Strained In/sub y/Ga/sub 1-y/As-GaAs quantum-well (InGaAs-QW) stripe geometry lasers ( lambda approximately 9050 AA) were fabricated by impurity-induced disordering (IID) through self-aligned Si-Zn diffusion. Lasers exhibit very low threshold (I/sub th/=3.0 mA at room-temperature continuous operation) and good uniformity (>90% with I/sub th/<8 mA, >70% with I/sub th/=4+or-1 mA). The moderate blue shift of the lasing wavelength (250 A or 40 meV) suggests that the strained InGaAs-QW active layer can survive long-time high-temperature thermal annealing (850 degrees C, 8 h) required for Si diffusion.<>