The neutron and electron radiation effects in Ill-V compound semiconductor
heterostructure devices are studied in this thesis. Three types of devices
investigated are AlGaAs/GaAs high electron mobility transistors (HEMTs),
AlGaAs/InGaAs/GaAs heterostructure insulated gate field effect transistors
(HIGFETs), and InP/InCaAs/InGaAs single heterojunction bipolar transistors
(SHBTs). HEMTs and HIGFETs are primarily investigated for neutron
irradiation effects. Detailed optimized processing of HEMT devices is introduced.
Numerical as well as analytical models that incorporate radiation
induced degradation effects in HEMTs and HIGFETs are developed.
The most prominent radiation effects appearing on both HEMT and HIGFET
devices are increase of threshold voltage (V[subscript T]) and decrease of transconductance
(g[subscript m]) as radiation dose increases. These effects are responsible for drain current
degradation under given bias conditions after irradiation. From our experimental
neutron irradiation study and our theoretical models, we concluded that
threshold voltage increase is due to the radiation-induced acceptor-like (negatively
charged) traps in the GaAs channel region removing carriers. The mobility
degradation in the channel is responsible for g[subscript m] decrease. Series resistance
increase is also related to carrier removal and mobility degradation. Traps introduced
in the GaAs region affect the device performance more than the traps
in the AlGaAs doped region. V[subscript T] and g[subscript m] of HIGFET devices are less affected
by neutron radiation than they are in HEMTs. This difference is attributed to
different shapes of the quantum well in the two devices.
The main effects of electron and neutron irradiation of SHBTs are decrease
of collector current (I[subscript c]), decrease of common-emitter DC gain, increase of the
collector output conductance (��I[subscript c]/��V[subscript CE]), and increase of collector-collector
offset voltage. The decrease of breakdown voltage of reverse biased base-emitter
junction diode is responsible for increasing the output conductance after irradiation.
Base-collector junction degradation also induces collector-emitter offset
voltage increase. / Graduation date: 2003
| Identifer | oai:union.ndltd.org:ORGSU/oai:ir.library.oregonstate.edu:1957/32545 |
| Date | 01 July 2002 |
| Creators | Jun, Bongim |
| Contributors | Subramanian, S. |
| Source Sets | Oregon State University |
| Language | en_US |
| Detected Language | English |
| Type | Thesis/Dissertation |
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