The electron, gamma and neutron radiation degradation of III-V semiconductors
and heterojunction bipolar transistors (HBTs) is investigated in this thesis.
Particular attention is paid to InP and InGaAs materials and InP/InGaAs
abrupt single HBTs (SHBTs). Complete process sequences for fabrication of
InP/InGaAs HBTs are developed and subsequently employed to produce the
devices, which are then electrically characterized and irradiated with the different
types of radiation. A comprehensive analytical HBT model is developed and radiation
damage calculations are performed to model the observed radiation-induced
degradation of SHBTs.
The most pronounced radiation effects found in SHBTs include reduction
of the common-emitter DC current gain, shift of the collector-emitter (CE) offset
voltage and increase of the emitter, base and collector parasitic resistances. Quantitative
analysis performed using the developed model demonstrates that increase
of the neutral bulk and base-emitter (BE) space charge region (SCR) components
of the base current are responsible for the observed current gain degradation. The
rise of the neutral bulk recombination is attributed to decrease in a Shockley-Read-Hall (SRH) carrier lifetime, while the SCR current increase is caused by rising SCR
SRH recombination and activation of a tunneling-recombination mechanism. On
the material level these effects are explained by displacement defects produced
in a semiconductor by the incident radiation. The second primary change of the
SHBT characteristics, CE offset voltage shift, is induced by degradation of the
base-collector (BC) junction. The observed rise of the BC current is brought on
by diffusion and recombination currents which increase as more defects are introduced
in a semiconductor. Finally, the resistance degradation is attributed to
deterioration of low-doped layers of a transistor, and to degradation of the device
metal contacts. / Graduation date: 2001
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/33262 |
| Date | 21 July 2000 |
| Creators | Shatalov, Alexei |
| Contributors | Sivaramakrishnan, Subramanian |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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