GaInP/GaAs HBTs
Graduate Students:
Apostolos Samelis,
Saeed Mohammadi
Professor
D. Pavlidis
U.S.Army Research Office DAAL03-92-G-0109, Thomson-CSF, Bell Northern Research
GaInP/GaAs has recently emerged as an alternative to AlGaAs/GaAs material
system for HBT power applications. The GaInP/GaAs system
has a larger valence band discontinuity than AlGaAs/GaAs. This results in
higher emitter injection efficiency and higher device gain.
Furthermore, due to the smaller conduction band discontinuity of
GaInP/GaAs, transport can be improved at higher current levels since,
injected electrons from the emitter to the base at these levels are less likely to
transfer to the L-valley of the GaAs base. Other
distinct advantages of GaInP/GaAs over AlGaAs/GaAs are the absence of
donor-related traps (DX centers) and the etching selectivity
of GaInP with respect to GaAs. Studies regarding the operation of
GaInP/GaAs HBTs are currently performed by use of Monte Carlo
and Drift-Diffusion simulation techniques. GaInP/GaAs HBT technology was
also recently developed in our laboratory. Devices are
fabricated using MOCVD and CBE grown wafers.
The suitability of Chemical Beam Epitaxy (CBE) for the growth of
GaInP/GaAs HBTs using an all organometallic approach is investigated. Reduced toxicity
tertiarybutylarsine (TBP) were used for group V sources. DC results
showed good base and collector current ideality factor of 1.23 and
1.05 respectively. The maximum dc current of 50 was obtained. A comparison of
these results with HBT characteristics obtained using AsH(3)/PH(3) of
TBA/PH(3) demonstrates the feasibility of replacing the toxic
AsH(3) and PH(3) by less toxic TBA and TBP sources in the growth of GaInP/GaAs
HBTs.
DC current gain as a function of base sheet resistance for AlGaAs/Gas and
GaInP/GaAs HBTs grown at different laboratories using different growth techniques.
Teh results show that HBTs fabricated using CBE and TBA, TBP precursors offer
for similar base sheet resistance values comparable gain Beta to that obtained
using other growth techniques and group V sources.
Bias dependence fT characteristic of a 3x50 um^2 self-aligned GaInP/GaAs HBT
fabricated using CBE grown layers with TBA, TBP precursors. Compared to
AlGaAs/GaAs HBTs made with similar geometries, these devices show very similar
characteristics.
[GaN]
[InP]
[GaAs]
[MOCVD]
[Mixer]
[Gunn (NDR)]
[PIN]
[HBTs]
[HEMTs]
[MMICs]
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Solid State Electronics Laboratory,
Department of Electrical Engineering and Computer Science,
University of Michigan
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