R.K. Montgomery

Growth of GaAs/AlGaAs HBTs by MOMBE (CBE)

Abstract In this paper, we will discuss how the unique growth chemistry of MOMBE can be used to produce high speed GaAs/AlGaAs heterojunction bipolar transistors (HBTs). The ability to grow heavily doped, well-confined layers with carbon doping from trimethylgallium (TMG) is a significant advantage for this device. However, in addition to high p-type doping, high n-type doping is also required. While elemental Sn can be used to achieve doping levels up to 1.5×10 19 cm -3 , severe segregation limits its use to surface contact layers. With tetraethyltin (TESn), however, segregation does not occur and Sn doping can be used throughout the device. Using these sources along with triethylgallium (TEG), trimethylamine alane (TMAA), and AsH 3 , we have fabricated Npn devices with 2 μm×10 μm emitter stripes which show gains of ≥ 20 with either ƒ t = 55 GHz and ƒ max = 70 GHz or ƒ t = 70 GHz and ƒ max = 50 GHz, depending upon the structure. These are among the best RF values reported for carbon doped HBTs grown by any method, and are the first reported for an all-gas source MOMBE process. In addition, we have fabricated a 70 transistor decision circuit whose performance at 10 Gb/s equals or exceeds that of similar circuits made from other device technologies and growth methods. These are the first integrated circuits reported from MOMBE grown material.

A DC to 20 GHz high gain monolithic InP/InGaAs HBT feedback amplifier

The authors have realized a high-gain, broadband, bipolar feedback amplifier exhibiting an average flatband gain of 30 dB with 6.5-dB/sub p-p/ ripple and a -3-dB bandwidth of 20 GHz. Using InP/InGaAs heterostructure bipolar transistors (HBTs), a gain-bandwidth product of more than 600 GHz was demonstrated for a nondistributed monolithic integrated circuit for the first time. This two-stage transadmittance-transimpedance design has a chip-size of 975 mu m*675 mu m and dissipates 280 mW for a 3-V supply. The input return loss and reverse transmission to 9 GHz were -30 dB and -40 dB, respectively.<<ETX>>

An edge-coupled receiver OEIC using AlInAs/InGaAs HBTs

The authors report on a novel edge-coupled optical receiver optoelectronic integrated circuit (OEIC) fabricated in AlInAs/InGaAs heterostructure bipolar transistor (HBT) technology. The edge coupled geometry is compatible with the multi-fiber array connector technology. The receiver consists of a waveguide pin detector, a transimpedance preamplifier and a second voltage amplifier stage. The pin has been realized in a standard HBT layer structure and requires no additional growth or processing steps.<<ETX>>

The effects of ionizing radiation on GaAs/AlGaAs and InGaAs/AlInAs heterojunction bipolar transistors

Abstract GaAs/AlGaAs and InGaAs/AlInAs Heterojunction Bipolar Transistors (HBTs) have been exposed to 60Co γ-ray doses up to 100 MRad. The d.c. current gain of GaAs/AlGaAs devices showed small increases for doses up to 75 MRad, due to a faster decrease in base current relative to collector current. After 100 MRad, none of the original devices were operational because of failure of the base-collector contact metallization (TiPtAu). Devices with either Be- or C-doped base layers showed the same response to the γ-ray doses. The InGaAs/AlInAs HBTs showed a small decrease ( ) in current gain after a total dose of 88 MRad and appear to be somewhat more resistant to damage from accumulated doses of radiation than comparable GaAs devices. GaAs/AlGaAs devices exposed to transient (120 nsec) pulses of high energy electrons show rapid recovery of both collector and base currents, with no long transient responses observed. Numerical simulations of the recovery of both GaAs- and InP-based HBTs after transient doses of ionizing radiation suggest that both are relatively immune to damage up to dose rates of 1011 Rad s−1 with faster recovery of the GaAs devices because of the shorter recombination times in this material.

High speed InGaAs HBT devices and circuits

An overview of the InGaAs heterostructure bipolar transistor (HBT) technology for applications in high speed electronics is presented. Properties of both Al/sub 0.48/In/sub 0.52/As-In/sub 0.53/Ga/sub 0.47/As and InP-In/sub 0.53/Ga/sub 0.47/As heterostructure systems, important for integrated circuit applications are discussed. Examples of high speed and low power integrated circuits that are relevant for lightwave communication technology are described.<<ETX>>

Ballistic transport effects in InP/GaInAs heterostructure bipolar transistors

The electron transport mechanism in the base (p=5/spl times/10/sup 19/cm/sup -3/) of GaInAs/InP heterojunction bipolar transistor was studied by the Monte Carlo method using the dielectric function response method. The self-consistent treatment included elastic and inelastic electron scattering. The room temperature transport was identified as ballistic for the base width less than 500 /spl Aring/. For the base width in the range of 500-2000 /spl Aring/ there are both ballistic and quasiballistic (hot electron diffusion) transport mechanisms. For the base width greater than 2000 /spl Aring/ we observe transport of thermalized electrons with long transit times. These results correlate well with the experimentally measured base delay times.<<ETX>>

InP/GaInAs composite collector heterostructure bipolar transistors and circuits

The authors investigate an alternative structure of a InP/GaInAs composite collector heterostructure bipolar transistor (CC HBT) which relied on a thin lightly doped quaternary layer of GaInAsP placed between GaInAs and InP regions of the collector instead of the doped interface. In this structure the accurate doping control of GaInAsP layer was not required. The resulting transistor showed high gain, high breakdown voltage BV/sub CEO/, f/sub T/ of 137 GHz and improved scalability characteristics. The usefulness of high speed CC HBTs for circuits was demonstrated by 28 GHz bandwidth, 39 db/spl Omega/ gain monolithic transimpedance amplifiers and 32 Gbit/s hybrid optical receivers.<<ETX>>

Low frequency noise and microwave properties of InP/InGaAs heterojunction bipolar transistors

Recent progress in the growth and processing of InP-based heterostructures has led to the design of heterojunction bipolar transistors (HBTs) with typical cutoff frequencies in excess of 100 GHz and current gains of 50-100. Besides the high frequency performance, the noise properties of the devices are significant for their use in mixers, local oscillators or amplifiers. Extensive studies of noise in AlGaAs/GaAs HBTs have been reported, which suggest that the low frequency noise is often dominated by generation-recombination type of noise due to traps in GaAs. Measurements on InP/InGaAs HBTs have shown lower noise as compared to AlGaAs/GaAs HBTs and evidence for recombination noise due to shallow traps. We present here experimental results on the frequency dependence of noise in InP/InGaAs HBTs from 0.1 Hz to 1 MHz. The purpose of this work is to identify the significant noise sources and to determine their dependence on external biasing conditions.<<ETX>>

Design trade-offs in InP based HBT ICs

The authors describe the current state of the art results and highlight design tradeoffs encountered for applications in analog, digital, and microwave circuits using InP based heterojunction bipolar transistors (HBTs). InP based HBTs are not merely devices for application in optoelectronic integrated circuits (OEICs). While the OEIC efforts continue, interest is increasing in very high performance systems for analog, digital, and power microwave applications. In the last year, significant improvements in device performance have been accomplished by grading the emitter-base junction and modifying the collector to enhance the breakdown performance. Issues of reliability are now getting attention and the technology is being applied more widely.<<ETX>>

Radiation Testing of AlInAs/lnGaAs and GaAs/AlGaAs HBTs

The radiation hardness of small geometry (∼2 × 4 μm 2 ), state of the art AlInAs/lnGaAs and GaAs/AlGaAs HBTs to 60 Co γ-ray has been investigated up to a dose of 100 MRad. The former devices showed a small change in I c and gain for 20 MRad, with essentially no change in I B . At 40 MRad, the gain of the devices had decreased to unity. By contrast, for GaAs/AlGaAs HBTs, the current gain actually increased up to a dose of 75 MRad. At 100 MRad, none of our devices were still operational. This was ascribed to degradation of the base-collector contact metallization (TiPtAu) and in particular to the presence of Au. Carbon-and beryllium-doped base devices showed the same response to 60 Co γ-ray doses. No long transient responses in either base or collector currents were observed during irradiation of the GaAs/AlGaAs devices with 120 nsec pulses of 10 MeV electrons at rates up to 2.7 × 10 10 Rad · sec −1 . Results of a 2-dimensional modelling study suggest that both GaAs and InP based HBTs are relatively immune to damage by transient radiation effects up to a dose rate of 10 11 Rad · sec −1 , with GaAs based devices being more resistant to radiation than InP due to their shorter recombination times.