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https://hdl.handle.net/2142/23948
Description
Title
Photo-hall studies of compound semiconductors
Author(s)
Kim, Matthew Hidong
Issue Date
1989
Doctoral Committee Chair(s)
Stillman, Gregory E.
Department of Study
Physics
Discipline
Physics
Degree Name
Ph.D.
Degree Level
Dissertation
Keyword(s)
III-V compound semiconductor
photo-Hall effect
GaAs
InP
epitaxial semiconductor
Language
en
Abstract
The III-V compound semiconductor materials are used in a wide variety of
electronic, optoelectronic and m1crowave device applications. Temperature
dependent photo-Hall effect measurements have been made on the high purity
compound semiconductors GaAs, InP and a ternary alloy In0 . 53Ga0 . 47As. The
major emphasis of this work involves the phenomenon of persistent photoconductivity.
This phenomenon has been used to facilitate the electrical
characterization of homogeneous and inhomogeneous thin epitaxial semiconductor
1 ayers. This effect 1s associated with a reduction 1n the surface and
substrate interface depletion that occurs upon illumination of the sample with
above band gap light at cryogen1c temperatures. After illumination, the
effects of a photoinduced charge neutral region persists, until at higher
temperatures, the sample relaxes back to its original state. For homogeneous
layers, the mobility , which is a measure of the microscopic quality of the
crystal, rema1ns unchanged after illumination. The persistent photoeffec t
strictly results from the increase 1.n the ef fee tive electrical thickness of
the layer. By utilizing the persistent photoeffect, electrical measurements
have been made on thin high purity GaAs, which was semi-insulating in the dark
because of surface and interface depletion.
The effects of illumination of inhomogeneous materials has also been
studied. Hall measurements on inhomogeneous GaAs and InP layers in the dark
show no unusual features. When these layers are illuminated with above band
gap light at low temperatures, anomalous values for the mobility and carrier
concentration have been measured. In one metalorganic chemical vapor
deposition (MOCVD) grown GaAs sample, the low temperature mobility was
decreased by two orders of magnitude after illumination. These particular
results have their origin in the occurrence of a accumulation of impurities at
the epilayer-substrate interface. The presence of this doping spike ~s not
detected when electrical measurements are made ~n the dark because of the
interface depletion.
These results clearly show that the persistent photo-Hall (i.e., Hall
data taken with momentary illumination of the sample with above band gap light
at low temperatures) H a powerful method for looking at the electrical
properties of thin high purity semiconductors.
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