掺In对反型AlGaAs/GaAs异质界面质量的改善及其应用

研究了AlGaAs层掺1%的In对AlGaAs/GaAs量子阱光致发光谱的半峰宽的影响.25K的光致发光结果表明,In作为表面活化剂能有效改善AlGaAs/GaAs异质界面的粗糙度.将此方法应用到反型AlGaAs/GaAs高电子迁移率晶体管(HEMT)材料结构中,Hall测量表明该方法能有效提高反型HEMT的电学性能.     

微空气桥隔离的自对准AlGaAs/GaAs异质结双极晶体管

利用微空气桥隔离和自对准技术成功地研制出了自对准结构的AlGaAs/GaAs异质结双极晶体管.器件展现出良好的直流和高频特性.对于发射极面积为2μm×15μm的器件,直流电流增益大于10,失调电压(Offsetvoltage)200mV;电流增益截止频率f_T大于30GHz,最高振荡频率f_max约为50GHz.     

高功率密度自对准结构AlGaAs/GaAs 异质结双极晶体管

利用各向异性的湿法刻蚀和侧墙隔离技术实现了发射极金属和基极金属的自对准,采用该自对准技术成功地研制出了自对准结构的AlGaAs/GaAs异质结双极晶体管,器件直流电流增益大于20,电流增益截止频率fT大于30GHz,最高振荡频率fmax大于50GHz,连续波功率测量表明：在1dB增益压缩时,单指HBT可以提供100mW输出功率,对应的功率密度为6.67W/mm,功率饱和时最大输出功率112mW,对应功率密度为7.48W/mm,功率附加效率为67%．     

AlGaAs/GaAs/AlGaAs渐变异质结光致发光仿真研究

分析了AlGaAs/GaAs/AlGaAs渐变异质结的光致发光特性。根据理论及仿真结果,确定了GaAs发光的最优能带结构为双异质结P-AlGaAs/P-GaAs/P-AlGaAs或者N-AlGaAs/N-GaAs/ N-AlGaAs,并且异质结两边能带渐变。基于所选结构,研究了能带渐变及层宽对发光效率的影响。研究结果表明,外体区吸收层的能带渐变,且外体区激发层的能带不变,发光区域的载流子最多,发光能量值最大。激励光源的波长不同,各层有不同的最优宽度,为器件的整体优化提供了依据。AlGaAs/GaAs/AlGaAs渐变异质结的光致发光研究为高效率器件如太阳电池、发光二极管等的实用化设计、研制提供了有价值的参考。     

RHEED优化MBE异质材料生长工艺

利用高能电子衍射振荡研究MBE异质材料生长工艺。优化了AlGaAs/InGaAs/GaAs材料生长工艺。通过霍耳测量、X射线双晶衍射及二次离子质谱研究了利用该工艺生长的AlGaAs/InGaAs/GaAs双δ掺杂PHEMT结构材料,获得了较好的材料参数。利用该材料研制器件也有较好的结果。     

微波、毫米波收发用的异质结双极晶体管

<正> 据日刊《电视学会志》1988年第7期报道,日本电气公司制成采用新结构的AlGaAs/GaAs异质结双极晶体管(HBT)的15GHz振荡器。用于卫星通信的收发系统,雷达装置等的微波、毫米波电路中带有振荡器的集成化很困难。在使用GaAs FET的时候,影响频率稳定度的相位噪声特性变坏,为使频率稳定,必须外接介质谐振器。该公司采用新结构的异质结晶体管解决了这个问题,为微波、毫米波电路全单片集成电路化奠定了基础。 新异质结双极晶体管用一块掩膜形成1μm以下微细结构的发射极、基极、收集极,并采用全对准技术。     

高截止频率异质结双极晶体管的研制

本文介绍了研制异质结双极晶体管(HBT)的工艺过程。使用MOCVD生长的GaAlAs/GaAs多层结构外延材料,采用离子注入隔离和湿法腐蚀技术,实现基极与发射极台面自对准工艺,研制出截止频率为22GHz的HBT。     

实用化AlGaAs/GaAs双异质结激光器

AlGaAs/GaAs双异质结激光器是光纤通信系统中的主要光源之一,它的万小时工作寿命的可信度是其主要关键指标。为此,国家科委和中国科学院给上海光机所下达了“实用化AlGaAs/GaAs双异质结激光器”的攻关任务,其中主要指标为万小时器件寿命的可信度达到85～90％。     

InGaAs／AlGaAs单量子阱激光器低阈值激射

研制了InGaAs/AlGaAs SQW激光器,对其工作特性如阈值电流密度、激射波长、特征温度、远场分布等进行了研究. 用MOCVD方法生长制备了InGaAs/AlGaAs分别限制单量子阱结构材料,得出其各层组分和能带分布.首先在GaAs衬底上生长GaAs缓冲层和AlGaAs波导层,然后生长窄能带的AlGaAs量子阱势垒层,再继续生长InGaAs量子阱有源区.其后继续生长AlGaAs势垒层、高Al组分AlGaAs波导层和GaAs高掺杂欧姆接触层.我们发现在低温范围里(160 K～220 K)阈值电流密度随温度升高而减小,与普通量子阱激光器正相反,表现出负的特征温度.随着温度进一步提高,阈值电流密度表现出指数式增大.300 K下腔长2000 μm的激光器最低的阈值电流密度约为200 A/cm2.(OD7)     

超低噪声毫米波PHEMT

以AlGaAs/InGaAs/GaAs为基础的十分之一微米栅长PHEMT器件在43GHz下提供了最优良的低噪声性能。测量的室温器件噪声系数为1.32dB(噪声温度=103K),相关增益6.7dB,在17K物理温度下,噪声系数为0.36dB(噪声温度=25K),相关增益为6.9dB,这是目前报道的43GHz下GaAs基器件的最低噪声系数。     

Etching behavior of GaAs/AlGaAs multilayer structure during laser beam scanning

The thermochemical etching behavior of GaAs/AlGaAs multilayer structure during laser beam scanning has been studied. The etch rate changes between GaAs and AlGaAs epilayers as the etching process proceeds through the layered sample. The phenomenon can be explained by the difference of thermal parameters of the heterojunction interface. The local temperature rise from laser irradiation has been calculated to investigate etching characteristics for GaAs and AlGaAs. It is concluded that the good thermal confinement at GaAs/AlGaAs interface produces the wider etch width of GaAs layer than that of AlGaAs layer in GaAs/AlGaAs multilayer. The maximum etch rate of the GaAs/AlGaAs multilayer was 32.5 μm/sec and the maximum etched width ratio of GaAs to AlGaAs was 1.7.     

Trap studies in GaInP/GaAs and AlGaAs/GaAs HEMT's by means oflow-frequency noise and transconductance dispersion characterizations

The presence of traps in GaInP/GaAs and AlGaAs/GaAs HEMT's was investigated by means of low frequency noise and frequency dispersion measurements. Low frequency noise measurements showed two deep traps (E _a1=0.58 eV, E_a2=0.27 eV) in AlGaAs/GaAs HEMT's. One of them (E_a2) is responsible for the channel current collapse at low temperature. A deep trap (E_a1'=0.52 eV) was observed in GaInP/GaAs HEMT's only at a much higher temperature (~350 K). These devices showed a transconductance dispersion of ~16% at 300 K which reduced to only ~2% at 200 K. The dispersion characteristics of AlGaAs/GaAs HEMT's were very similar at 300 K (~12%) but degraded at 200 K (~20%). The low frequency noise and the transconductance dispersion are enhanced at certain temperatures corresponding to trap level crossing by the Fermi-level. The transition frequency of 1/f noise is estimated at 180 MHz for GaInP/GaAs HEMT's and resembles that of AlGaAs/GaAs devices     

Ga0.51In0.49P/GaAs HEMT's exhibiting goodelectrical performance at cryogenic temperatures

The DC and microwave characteristics of Ga_0.51In_0.49P/GaAs HEMTs grown by metalorganic chemical vapor deposition (MOCVD) are presented. Devices with 1-μm-long gates show transconductances of 163 and 213 mS/mm at 300 and 77 K, respectively. Their maximum cutoff frequency is 17.8 GHz. Deep traps in the doped layer are evaluated at low temperature by the threshold voltage shift and current collapse phenomena. GaInP/GaAs HEMTs show no current collapse and have almost zero threshold voltage shift compared to AlGaAs/GaAs and InAlAs/InGaAs where the corresponding values are 0.5 and 0.25 V, respectively     

An 18-34-GHz dynamic frequency divider based on 0.2-μmAlGaAs/GaAs/AlGaAs quantum-well transistors

The design and performance of a dynamic frequency divider was presented. This digital IC demonstrates the ability of the authors' AlGaAs/GaAs/AlGaAs quantum-well FETs with gate lengths of 0.2 μm. Stable operation was achieved in the frequency range from 18 GHz up to 34 GHz with a power consumption of 250 mW. To the authors' knowledge, this is the best result ever reported for HEMT circuits, and is similar to the frequency limit achieved by use of AlGaAs/GaAs HBTs     

空间生长GaAs单晶做衬底的GaAs/AlGaAs DH激光器

我们首次用在中国返地卫星上生长的Si-GaAs单晶做衬底,成功地研制出室温CW工作的GaAs/AlGaAs质子轰击条形DH激光器,DH外延片是用LPE法生长的。激光器的最低阈电流20mA,激射波长857nm,输出功率可达30mW。     

A high-speed frequency divider using n+-Ge Gate AlGaAs/GaAs MISFET's

A high-speed divide-by-four static frequency divider is fabricated using n+ -Ge gate AlGaAs/GaAs heterostructure MISFET's. The divider circuit consists of two master-slave T-type flip-flops (T-FF's) and an output buffer based on source-coupled FET logic (SCFL). A maximum toggle frequency of 11.3 GHz with a power dissipation of 219 mW per T-F/F is obtained at 300 K using 1.0-µm gate FET's.     

Characterization of InGaAs/AlGaAs pseudomorphic modulation-doped field-effect transistors

High-performance pseudomorphic InyGa1-yAs/Al0.15- Ga0.85As (0.05 le y le 0.2) MODFET's grown by MBE have been characterized at dc (300 and 77 K) and RF frequencies. Transconductances as high as 310 and 380 mS/mm and drain currents as high as 290 and 310 mA/mm were obtained at 300 and 77 K, respectively, for 1-µm gate lengths and 3-µm source-drain spacing devices. Lack of persistent trapping effects,I-Vcollapse, and threshold voltage shifts observed with these devices are attributed to the use of low mole fraction AlxGa1-xAs while still maintaining 2DEG concentrations of about 1.3 × 10¹²cm^-2. Detailed microwave S-parameter measurements indicate a current gain cut-off frequency Of 24.5 GHz Wheny = 0.20, which is as much as 100 percent better than similar GaAs/AlGaAs MODFET structures, and a maximum frequency of oscillation of 40 GHz. These superior results are in part due to the higher electron velocity of InGaAs as compared with GaAs. Velocity field measurement performed up to 3 kV/cm using the magnetoresistance method indicates an electron saturation velocity of greater than 1.7 × 10⁷cm/s at 77 K fory = 0.15, which is 20 percent higher than GaAs/AlGaAs MODFET's of similar structure.     

Enhanced microwave performance of ion-implanted MESFET with graded GaAs/AlGaAs heterojunctions

Ion-implanted MESFETs have been fabricated on an inverted GaAs/AlGaAs heterostructure. The aluminium concentration in the AlGaAs is graded from 0% at the substrate to 30% at the heterointerface. A maximum extrinsic transconductance of 410 mS/mm is achieved with 0.5 mu m gate devices. This heterojunction ion-implanted FET (HIFET) also exhibits enhanced microwave performance, especially at low drain current, when compared to conventional ion-implanted GaAs MESFETs. At 20% of I/sub dss/, the current gain cutoff frequency f/sub t/ is 40 GHz, which increases up to a maximum value of 47 GHz as the drain current rises. These characteristics of high f/sub t/ and high gain at low current are advantageous for low-noise applications.<>     

Properties of MODFET's grown on Si substrates at DC and microwave frequencies

We report the first microwave characterization of 1-µm gate GaAs/AlGaAs modulation-doped field-effect transistors (MODFET's) grown on Si substrates by MBE. Maximum transconductances of 170 mS/mm at room temperature were obtained in structures on Si, which compares to values of 200-250 mS/mm for this type of structure on GaAs. At 77 K, no collapse was observed in these structures, and transconductances of 270 mS/mm were obtained. From microwave S-parameter measurements at room temperature, current gain cutoff frequencies of 15 GHz were obtained from these GaAs/AlGaAs MOD FET's on Si, which compares with 12-15 GHz obtained on GaAs substrates. From high-frequency equivalent circuit modeling, very little difference was observed in any of the parameters between growth on Si and on GaAs. This is significant in that it demonstrates the suitability of GaAs on Si for device applications.