Growth and metallization of AlGaAs/GaAs carbon-doped HBTs usingtrimethylamine alane by CBE

It is shown that the entire structure of high-quality AlGaAs/GaAs heterojunction bipolar transistors (HBTs) including a nonalloyed δ-doped ohmic contact and in-situ Al metallization can be grown by chemical beam epitaxy (CBE) using a new precursor, trimethylamine alane, as the Al source. The graded Al_xGa_1-xAs and uniform GaAs bases (both ~1000 A thick) are doped with carbon to high 10 ¹⁹ cm^-3 using trimethyl-Ga. A current gain of 10 at a current density of 2500 A/cm² is obtained for both uniform- and graded-base HBTs. Both devices show good output characteristics     

A low-gate-leakage-current GaAs MESFET with a thin epitaxialsilicon layer

An n-channel depletion-mode GaAs MESFET with an Al gate and a 6-A epitaxial Si layer between the metal and the GaAs, grown in situ by molecular beam epitaxy, is described. Its DC electrical characteristics are compared with a similar control structure grown without the Si layer. The gate leakage current in the Al/Si/GaAs MESFETs was three to four orders of magnitude lower than in the control structure, due to all increased barrier height in the Al/Si/n-GaAs Schottky gate of 1.04 eV, versus 0.78 eV for the Al/n-GaAs structure. The differences in threshold voltages, I-V characteristics, and transconductances between the two devices are consistent with an enhanced effective barrier height for the Al/Si/GaAs MESFET     

Al_xGa_(0.52-x)In_(0.48)P/GaAs异质结双极晶体管高温特性的计算分析

建立了适用于缓变 Alx Ga0 .5 2 -x In0 .48P/Ga As HBT的解析模型。考虑了 Al组分 x的变化对 HBT温度特性的影响。分析结果表明 ,在实用的电流范围 (Jc在 1 0 3 A/cm2 左右 )内 ,Alx Ga0 .5 2 -xIn0 .48P/Ga As HBT随着 x的增大 ,其电流增益的稳定性也上升 ,当 x=0 .3时工作温度可超过 70 0K。文章还分析了高温时 HBT电流增益下降的原因     

Microwave performance of 0.4 mu m gate metamorphic In/sub 0.29/Al/sub 0.71/As/In/sub 0.3/Ga/sub 0.7/As HEMT on GaAs substrate

MBE grown metamorphic In/sub 0.29/Al/sub 0.71/As/In/sub 0.3/Ga/sub 0.7/As/GaAs high electron mobility transistors (HEMTs) have been successfully fabricated. A 0.4 mu m triangular gate device showed transconductance as high as 700 mS/mm at a current density of 230 mA/mm. The measured f/sub T/ was 45 GHz and f/sub max/ was 115 GHz. These high values are, to the authors knowledge, the first reported for submicrometre metamorphic InAlAs/InGaAs/GaAs HEMTs with an indium content of 30%.<>     

GaInAsP过渡层在808 nm GaAsP/(Al)GaInP半导体激光器中降电压的应用

利用金属有机化学气相沉积的方法在GaAs衬底上生长了GaInAsP外延层及GaAsP/(Al)GaInP激光器外延层。生长的GaInAsP外延层与GaAs晶格匹配,并且带隙处于Ga_0.5In_0.5P与GaAs中间。在GaInP/GaAs异质结界面插入此结构的GaInAsP过渡层,可以有效的降低异质结的带阶,尤其是价带带阶。相比于突变GaInP/GaAs异质结的808 nm GaAsP/(Al)GaInP半导体激光器,含有GaInAsP过渡层的半导体激光器具有更低的工作电压。因此,在350 mW输出功率下,半导体激光器的功率转换效率由52%提高至60%。并且在大电流注入下,含有GaInAsP过渡层的半导体激光器由于产生的焦耳热减少,具有更高的输出功率。     

High temperature characteristics of strained InGaAs/lnGaAsP quantumwell lasers lattice matched to GaAs

The effect of high temperature on the threshold current density and the gain of In_xGa_1-xAs/InGaAsP (E_g=1.6 eV) QW lasers lattice matched to GaAs is investigated theoretically. These results are also compared with those of In_x Ga_1-xAs/GaAs QW lasers. It is found that better performance can be achieved in InGaAs/InGaAsP lasers compared to InGaAs/GaAs lasers at high temperature. This is due to the fact that the temperature dependence of the threshold carrier density for InGaAs/InGaAsP lasers is weaker than that for InGaAs/GaAs lasers. The calculated characteristic temperature is in good agreement with reported experimental results     

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/.<>     

In0.5(AlxGa1-x)0.5HEMTs for high-efficiency low-voltage power amplifiers: design,fabrication, and device results

In_0.5(Al_xGa_1-x)_0.5 high electron-mobility transistors (HEMTs) are expected to have higher two-dimensional electron gas density and larger current drive capability than both Al_0.23Ga_0.77As and In_0.5Ga _0.5P HEMTs due to the improved conduction-band offsets. In this paper, we performed a systematic investigation of the electrical properties of In_0.5(Al_xGa_1-x)_0.5 P (0⩽x⩽1) material system lattice matched to GaAs. By considering the conduction-band offset, direct-to-indirect-band electron transfer, donor-related deep levels, and Schottky barrier height, a relatively narrow range of the Al content 0.2⩽x⩽0.3 was found to be the optimum for the design of In_0.5(Al_xGa_1-x)_0.5 HEMTs. Under 1.2-V operation, power transistors with the optimum aluminum composition show high drain current density, high transconductance, and excellent power-added efficiency (65.2% at 850 MHz). These results demonstrate that InAlGaP HEMTs are promising candidates for high-efficiency low-voltage power applications     

一种新材料结构的RTD器件的设计及实现

设计了一种带有Al0.22Ga0.78As/In0.15Ga0.85As/GaAs发射极空间层和GaAs/In0.15Ga0.85As/GaAs量子阱的共振隧穿二极管(RTD)材料结构,并且成功地制作了相应的RTD器件.在室温下,测试了RTD器件的直流特性,计算了RTD器件的峰谷电流比和可资电流密度.在分析器件特性的基础上,指出调整材料结构和优化工艺参数将进一步提高RTD器件的性能.     

Design and Realization of Resonant Tunneling Diodes with New Material Structure

A new material structure with Al0.22Ga0.78As/In0.15Ga0.85As/GaAs emitter spacer layer and GaAs/In0.15Ga0.85As/GaAs well for resonant tunneling diodes is designed and the corresponding device is fabricated.RTDs DC characteristics are measured at room temperature. Peak to valley current ratio and the available current density for RTDs at room temperature are computed.Analysis on these results suggests that adjusting material structure and optimizing fabrication processes will be an effective means to improve the quality of RTDs.     

Effects of impact ionization on I-Vcharacteristics of GaAs n-i-n structures including hole trap

Numerical simulations of GaAs n-i-n structures with Cr deep acceptors (hole trap) in the i-layer are performed by considering the impact ionization of carriers. At low voltages, I-V curves show sublinear or saturated features, because the voltage is entirely applied along the reverse-biased n-i junction. When the deep-acceptor density is low, a steep rise of current occurs due to trap filling, whereas when the deep-acceptor density becomes high, the steep current rise occurs due to impact ionization of carriers at the reverse-biased n-i junction. In this case, the voltage for current rise becomes lower as the acceptor density becomes higher     

GaAs MOSFET using InAlP native oxide as gate dielectric

GaAs metal-oxide-semiconductor field-effect transistors (MOSFETs) using wet thermally oxidized InAlP as the gate insulator are reported for the first time. Leakage current measurements show that the 11-nm-thick native oxide grown from an In/sub 0.49/Al/sub 0.51/P layer lattice-matched to GaAs has good insulating properties, with a measured leakage current density of 1.39/spl times/10/sup -7/ mA//spl mu/m/sup 2/ at 1 V bias. GaAs MOSFETs with InAlP native gate oxide have been fabricated with gate lengths from 7 to 2 /spl mu/m. Devices with 2-/spl mu/m-long gates exhibit a peak extrinsic transconductance of 24.2 mS/mm, an intrinsic transconductance of 63.8 mS/mm, a threshold voltage of 0.15 V, and an off-state gate-drain breakdown voltage of 21.2 V. Numerical Poisson's equation solutions provide close agreement with the measured sheet resistance and threshold voltage.     

60-GHz high power performance In/sub 0.35/Al/sub 0.65/As-In/sub 0-35/Ga/sub 0.65/As metamorphic HEMTs on GaAs

We report on a double-pulse doped, double recess In/sub 0.35/Al/sub 0.65/As-In/sub 0.35/Ga/sub 0.65/As metamorphic high electron mobility transistor (MHEMT) on GaAs substrate. This 0.15-/spl mu/m gate MHEMT exhibits excellent de characteristics, high current density of 750 mA/mm, extrinsic transconductance of 700 mS/mm. The on and off state breakdown are respectively of 5 and 13 V and defined It gate current density of 1 mA/mm. Power measurements at 60 GHz were performed on these devices. Biased between 2 and 5 V, they demonstrated a maximum output power of 390 mW/mm at 3.1 V of drain voltage with 2.8 dB power gain and a power added efficiency (PAE) of 18%. The output power at 1 dB gain compression is still of 300 mW/mm. Moreover, the linear power gain is of 5.2 dB. This is to our knowledge the best output power density of any MHEMT reported at this frequency.     

High peak-to-valley current ratio AlGaAs/AlAs/GaAs double barrier resonant tunnelling diodes

A double barrier resonant tunnelling diode with the highest room temperature peak-to-valley current ratio using Al/sub x/Ga/sub 1-x/As/GaAs quantum wells is reported. Room temperature peak-to-valley ratios of 6.3 were obtained using an Al/sub 0.2/Ga/sub 0.8/As 'chair' barrier. Peak current density for these diodes was typically 30 kA/cm/sup 2/.<>     

Al/SiC carriers for microwave integrated circuits by a new technique of pressureless infiltration

Materials with high thermal conductivity and thermal expansion coefficient matching with that of Si or GaAs are being used for packaging high density microcircuits due to their ability of faster heat dissipation. Al/SiC is gaining wide acceptance as electronic packaging material due to the fact that its thermal expansion coefficient can be tailored to match with that of Si or GaAs by varying the Al:SiC ratio while maintaining the thermal conductivity more or less the same. In the present work, Al/SiC microwave integrated circuit (MIC) carriers have been fabricated by pressureless infiltration of Al-alloy into porous SiC preforms in air. This new technique provides a cheaper alternative to pressure infiltration or pressureless infiltration in nitrogen in producing Al/SiC composites for electronic packaging applications. Al-alloy/65vol% SiC composite exhibited a coefficient of thermal expansion of 7/spl times/10/sup -6/ K/sup -1/ (25/spl deg/C-100/spl deg/C) and a thermal conductivity of 147 Wm/sup -1/K/sup -1/ at 30/spl deg/C. The hysteresis observed in thermal expansion coefficient of the composite in the temperature range 100/spl deg/C-400/spl deg/C has been attributed to the presence of thermal residual stresses in the composite. Thermal diffusivity of the composite measured over the temperature range from 30/spl deg/C to 400/spl deg/C showed a 55% decrease in thermal diffusivity with temperature. Such a large decrease in thermal diffusivity with temperature could be due to the presence of micropores, microcracks, and decohesion of the Al/SiC interfaces in the microstructure (all formed during cooling from the processing temperature). The carrier showed satisfactory performance after integrating it into a MIC.     

共振隧穿二极管电流密度-电压曲线的计算与分析

用紧束缚能带方法计算双势垒结构 Ga As/ Ga1-x Alx As/ Ga As和 In As/ Ga Sb/ Al Sb的电子、空穴电流密度 ,对计算结果进行分析 ,并对其结果在工艺设计中的应用进行讨论     

Modification of GaAs Schottky barriers using a-Si:H interfaciallayers

The electrical characteristics of metal/a-Si:H/n-GaAs diode structures were studied in order to investigate the role of the a-Si:H and the claim of no barrier at the GaAs/a-Si:H interface. Diodes were fabricated using a-Si:H layers between 30 and 1920 Å thick, with Al and Mg metallization, and the current-voltage and capacitance-voltage characteristics were examined. Rectifying Schottky barriers were formed at Al/a-Si:H junctions, while good ohmic contacts were formed at Mg/a-Si:H junctions, enabling effects due to the metal/a-Si:H and a-Si:H/GaAs interface to be isolated. A dramatic increase in the forward turn-on voltage was observed as the thickness of the a-Si:H layer increased. The diode behavior can be explained by considering three effects in series: (1) an a-Si:H/GaAs barrier of about 0.6 eV, consistent with Fermi-level pinning in GaAs; (2) a metal/a-Si:H barrier, dependent on the metallization; and (3) space-charge-limited current (SCLC) in the bulk a-Si:H. The SCLC effectively gives rise to a voltage-dependent resistance and causes the increased turn-on voltages     

Investigation of indium doping and incorporation in AlGaAs/GaAs double-barrier resonant tunnelling structures

In doping and incorporation in the barrier layers of AlGaAs/GaAs double-barrier resonant tunnelling structures (DBRTSs) have been studied. It was found that the peak-to-valley current ratio (PVCR) can be improved by the proper amount of In doping. This is attributed to the improvement in the quality of the AlGaAs barrier layers due to the high surface migration rate of In atoms that reduces group III vacancies. Also pseudomorphic In/sub x/(Al/sub 0.5/Ga/sub 0.5/)/sub 1-x/As/GaAs (x=0.12) strained-layer DBRTSs have been fabricated by incorporating a sufficient amount of In into the AlGaAs barrier layers. PVCRs as high as 27.5 at 77 K have been obtained. This is the first realisation of such DBRTSs with lattice-mismatched quaternary barrier layers.<>     

Analysis of Optically Controlled Microwave/Millimeter-Wave Device Structures

Light-induced voltage and the change in the source-to-drain channel current under optical illumination higher than the semiconductor band gap for GaAs MESFET, InP MESFET, Al/sub 0.3/Ga/sub 0.7/As/GaAs high electron mobility transistor (HEMT), and GaAs permeable base transistor (PBT) are analytically obtained. The GaAs PBT and GaAs MESFET have higher sensitivity than the InP MESFET. However, the Al/sub 0.3/Ga/sub 0.7/As/ GaAs HEMT is observed to have the highest sensitivity. Variations in the small-signal parameters, such as channel conductance, gate-to-source capacitance, and transconductance, as well as transient parameters, such as switching time and power-delay product, of GaAs MESFET with illumination are computed. The computed capacitance and transconductance are compared with the experimentally obtained values and are found to be in fair agreement. Based on these results, the design considerations for an optically controlled MESFET switch are discussed. Finally, variation in device parameter due to optical illumination and its effect on the cutoff frequencies f/sub T/ and f/sub max/ are also investigated.     

Heterojunction bipolar transistor using a (Ga,In)P emitter on a GaAs base, grown by molecular beam epitaxy

We report the first N-p-n heterojunction bipolar transistor (HBT) using a (Ga,In)P/GaAs heterojunction emitter on a GaAs base. This combination is of interest as a potential alternate to (Al,Ga)As/GaAs, because of theoretical predictions of a larger valence band discontinuity and a smaller conduction band discontinuity, thus eliminating the need for grading of the emitter/base junction. The structure was grown by molecular beam epitaxy, with the base doping (∼10¹⁹cm^-3) far exceeding the n-type doping ∼5¹⁷cm^-3) of the (Ga,In)P wide gap emitter (Eg= 1.88 eV). Common-emitter current gains of 30 were attained at a current density of 3000 A/cm², the highest current density achieved without burnout.