Base-emitter diffusion capacitance in GaAlAs/GaAs HBTs

The voltage dependence of the base-emitter diffusion capacitance in a single heterojunction GaAlAs/GaAs HBT is discussed. It is found that conventional transistor capacitance models are not accurate for these devices. An empirical expression is given which may be used to model this diffusion capacitance.<>     

An introduction to GaAs/GaAlAs HBTs for power applications

This paper presents a brief introduction to GaAs/GaAlAs heterojunction bipolar transistors (HBTs) for microwave and millimetre-wave power applications. The theoretical advantages of the heterojunction are outlined and the benefits of its incorporation in DC, RF and power devices are discussed. The problems inherent in the realization of HBTs in terms of device design, epitaxial material growth and device fabrication are discussed and the performance characteristics for practical devices presented. The paper concludes with a look at state-of-the-art GaAs/GaAlAs HBT performance and its standing with respect to the competing technologies of the metal semiconductor field effect transistor (MESFET) and the high electron mobility transistor (HEMT).     

GaAlAs／GaAsHBT的现状和应用展望

本文评述了GaAlAs/GaAs HBT的研究现状,着重讨论了制造HBT的重要技术和应用前景;对HBT的进一步发展也进行了探讨。     

A study of L-band GaAlAs/GaAs HBTs for high-voltage RF-power

The feasibility of GaAlAs/GaAs heterojunction bipolar transistors as power output transistors for 24–28V cellular base station applications was studied. A 1W, 25V test vehicle was fabricated, with predictable and uniform electrical parameters. Maximum output power was 1.02W with 9.1dB gain at 2GHz and 18V supply voltage. Characterization at more than 22V destroyed all devices, even if emitter ballasting resistors were used for thermal balance. Analysis indicated that the failures were caused by too wide emitters in combination with the high supply voltage, causing current crowding and large temperature spikes. Small (<2-3µm) horizontal emitter dimensions are required even with low base sheet resistivity, otherwise leading to destructive temperature non-uniformities, unless special arrangements to drastically reduce the thermal resistance can be applied.     

GaAs/GaAlAs active-passive-interference laser

A GaAs/GaAlAs interference laser with an active and a passive section is reported. A very clean single longitudinal mode is obtained and maintained without mode hopping over about 10°C, which results from the combined effect of interference and real index waveguiding in the lateral direction.     

Luminescence of stepped quantum wells in GaAs/GaAlAs and InGaAs/GaAs/GaAlAs structures

Luminescence spectra of doped and undoped GaAs/GaAlAs and InGaAs/GaAs/GaAlAs structures containing several tens of stepped quantum wells (QW) are investigated. The emission bands related to free and bound excitons and impurity states are observed in QW spectra. The luminescence excitation spectra indicate that the relaxation of free excitons to the e1hh1 state proceeds via the exciton mechanism, whereas an independent relaxation of electrons and holes is specific to bound excitons and impurity states. The energy levels for electrons and holes in stepped QWs, calculated in terms of Kane’s model, are compared with the data obtained from the luminescence excitation spectra. The analysis of the relative intensities of emission bands related to e1hh1 excitons and exciton states of higher energy shows that, as the optical excitation intensity increases, the e1hh1 transition is more readily saturated at higher temperature, because the lifetime of excitons increases. Under stronger excitation, the emission band of electron-hole plasma arises and increases in intensity superlinearly. At an excitation level of ～10⁵ W/cm², excitons are screened and the plasma emission band dominates in the QW emission. Nonequilibrium luminescence spectra obtained in a picosecond excitation and recording mode show that the e1hh1 and e2hh2 radiative transitions are 100% polarized in the plane of QWs.     

非对称大光腔GaAlAs／GaAs激光器分析与实验

本文分析了非对称大光腔结构在提高ＧａＡｌＡｓ／ＧａＡｓ激光器输出光功率方面的优越性。计算了为获得最大功率和基模工作所应选用的有关参数。在上述分析的基础上，研制了非对称大光腔（Ａ－ＬＯＣ）ＧａＡｌＡｓ／ＧａＡｓ激光器，其未涂覆输出光功率达８５ｍＷ以上，这一结果与理论计算基本符合。     

Electron space-charge effects on high-frequency performance ofAlGaAs/GaAs HBTs under high-current-density operation

The high-frequency characteristics of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) under high-current-density biasing condition are investigated in conjunction with the electron space charge in the collector depletion layer. A significant increase in cutoff frequency f_t and maximum oscillation frequency f_max at the early stage of the base push-out was observed in HBTs with a lightly doped n-type collector structure, and is attributed to the collector depletion layer widening and the enhancement of the velocity overshoot effect caused by the increasing electron density     

GaAs/GaAlAs curved rib waveguides

Curved dielectric optical waveguides suffer from radiation loss due to bending. To minimize the bending loss and reduce the radius of curvature, it is necessary to fabricate guides which provide strong optical confinement. This paper gives a brief review of curved waveguide analysis and presents some experimentally measured loss values for GaAs/GaAlAs curved rib waveguides. The rib waveguides, fabricated using ion beam milling, have a large rib height and are tightly guided structures. When corrected for reflection losses and input coupling efficiency, a minimum loss of approximately 3 dB has been achieved for a multimode 90° curved guide with a radius of curvature of 300 μm, and 8.5 dB for a single-mode curved guide with a radius of curvature of 400 μm. It is believed that most of this residual loss is not radiation loss due to bending, but rather scattering loss due to rib wall imperfections.     

AlGaAs/GaAs HBT的设计研究

利用BIPOLE计算机程序,评价了具有不同版图、不同掺杂分布和不同层厚的AlGaAs/GaAs HBT的频率性能,研究了HBT的最佳化设计,并比较了HBT和多晶硅发射极晶体管的大电流性能。研究表明,对发射极条宽S_E<3μm的HBT来说,在电流密度小于1×10~5A/cm~2时,并未发现电流集聚效应,由最高f_T确定的HBT电流处理容量要比多晶硅发射极晶体管的大两倍多。对基区掺杂为1×10~(19)cm~(-3)的典型工艺n-p-n型AlGaAs/GaAs HBT,已获得了一个最佳化的最高振荡频率f_(mos(?))的方程式:f_(mosc)=337(W_(Bop)/S_E)~(1/2)GHz,式中,W_(Bop)是最佳基区宽度,S_E是发射极条宽,二者都以微米为单位。     

Breakdown behavior of GaAs/AlGaAs HBTs

Avalanche breakdown behavior at the collector junction of the GaAs/AlGaAs HBT (heterojunction bipolar transistor) has been studied. Junction breakdown characteristics displaying hard breakdown, soft breakdown, and negative resistance breakdown behavior were observed and are interpreted by analysis of localized microplasma effects, uniform microplasma-free behavior, and associated current gain measurements. Light emission from the collector-base junction of the GaAs/AlGaAs HBT was observed and used to investigate breakdown uniformity. Using a simple punchthrough breakdown model, the theoretical breakdown curves at different collector doping concentrations and thicknesses were computed and found to be in agreement with maximum breakdown voltages measured from devices displaying the most uniform junction breakdown. The serious current gain degradation of GaAs/AlGaAs HBTs at low current densities was analyzed in connection with the measurement of a large collector-emitter breakdown voltage. The unexpected functional relationship between the collector-emitter breakdown voltage and collector-base breakdown voltage is explained by the absence of a hole-feedback effect for devices not exhibiting transistor action     

Design study of AlGaAs/GaAs HBTs

The frequency performance of AlGaAs/GaAs heterojunction bipolar transistors (HBTs) having different layouts, doping profiles, and layer thicknesses was assessed using the BIPOLE computer program. The optimized design of HBTs was studied, and the high current performances of HBTs and polysilicon emitter transistors were compared. It is shown that no current crowding effect occurs at current densities less than 1×10⁵ A/cm² for the HBT with emitter stripe width S_E<3 μm, and the HBT current-handling capability determined by the peak current-gain cutoff frequency is more than twice as large as that of the polysilicon emitter transistor. An optimized maximum oscillation frequency formula has been obtained for a typical process n-p-n AlGaAs/GaAs HBT having base doping of 1×10 ¹⁹ cm^-3     

4GHz300mW InGaP/GaAs HBT功率管研制

通过采用发射极-基极金属自对准、发射极镇流电阻,电镀空气桥等工艺改善了器件的高频特性,提高了器件热稳定性与功率特性.当器件工作在AB类,工作频率为4 GHz,集电极偏置电压为3.5 V时,尺寸为16×(3 μm×15 μm)的功率管获得了最大输出功率为24.9 dBm(309.0 mW)、功率增益为8.1dB的良好性能.     

Mach-Zehnder型GaAs／GaAlAs行波光调制器的微波特性分析

提出利用n+重掺杂层的慢波效应研制Mach-Zehnder干涉型行波光调制器,并通过在相对介电常数εr中引入与电导率有关的虚部σ／ωε0,拓展了直线法对介质损耗的计算。文中指出在这种共面微带线中奇模和偶模的不同作用,重点分析和研究了器件行波电极的微波特性．从而设计出理论上可达46GHz带宽的高速光波导调制器。     

GaAlAs/GaAs heterojunction microwave bipolar transistor

A GaAlAs/GaAs heterojunction bipolar transistor has been developed and tested. A double base structure was adopted to facilitate critical selective etching problems. An emitter-collector breakdown voltage VCEO as high as 80 V was achieved. Maximum frequency of oscillationfmax of 850 MHz and a cutoff frequency fT of 1.6 GHz were realised. The current-gain/temperature curve shows that the transistor can be operated at temperatures up to 350°C.     

透射窗口型GaAs/GaAlAs掩埋异质结构激光器

本文通过耦合速率方程组,从原理上分析了扩展半导体激光器调制带宽的三个根本途径,在理论计算的基础上给出本结构激光器的具体设计方案。最后介绍了器件的制作工艺和工作特性。     

高功率GaAlAs／GaAs量子阱SCH半导体激光器

利用分子束外延生长装置生长出了ＧａＡｌＡｓ／ＧａＡｓ梯度折射分别限制（ＧＲＩＮ－ＳＣＨ）单量子阱结构材料。样品的测试结果表明,样品质量达到了设计要求。利用该材料制作的激光二极管,室温连续工作,功率为１Ｗ,斜率效率达到１．０４Ｗ／Ａ。     

High-efficiency millimeter-wave GaAs/GaAlAs power HEMT's

The power, gain, and efficiency of 0.5-µm gate-length, 75- and 50-µm gate-width multiple heterojunction high electron mobility transistors (HEMT's) have been evaluated from 10 to 60 GHz. At 10 GHz, with a source-to-drain voltage as low as 2.4 V, the device delivers a power density of 0.37 W/mm with 13.4-dB gain and 60.8-percent efficiency. At 60 GHz, a 50-µm device gave 0.4 W/mm with 3.6-dB gain and 14-percent efficiency. The power density and efficiency of these 0.5- µm gate-length HEMT's above 40 GHz are the best reported for a three-terminal device. Fundamental frequency oscillations up to 104 GHz were observed when a device was bonded as a free-running oscillator.     

Proton-bombardment isolated GaAlAs/GaAs charge-coupled devices

Proton bombardment is used for the first time as a channel isolation technique to fabricate buried channel homojunction charge-coupled devices (c.c.d.s) of n-GaAs channel on GaAs substrate and heterojunction c.c.d.s of n-Ga1?xAlxAs on GaAs. The c.c.d. structure is a Schottky-barrier gate buried channel 3-phase device with 30 transfer gates. The channel-stop bombardment was carried out at room temperature with an energy of 200 keV and a total dose of 1015/cm2. The c.c.d.s were tested with electrical charge injection and direct readout. The charge transfer efficiency was found to be greater than 0.999 per transfer for both GaAs and GaAlAs. The proton-bombardment isolated devices were compared with similar devices using mesa isolation and were found to perform similarly.     

Analysis of the electrical characteristics of GaInP/GaAs HBTs including the recombination effect

An analytical model is used to predict the effects of surface recombination current on the gain and transit time of GaInP/GaAs heterojunction bipolar transistors (HBTs). The present analysis shows that consideration of the recombination current gives current gain values that are comparable to those of the experimental results. The dependence of current gain on temperature, base doping and emitter area are also analyzed, and the variation in collector current with emitter-base voltage, temperature and doping is considered.