Study of elastic properties of semiconductors by surface Brillouin scattering
Date
2010-09-07
Authors
Kotane, Lesias Morake
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Abstract
Surface Brillouin scattering (SBS) has been used to investigate the elastic properties
of two semiconductors.
Boron doped polycrystalline silicon is a widely used material for
microelectromechanical systems (MEMS) devices. SBS measurements were carried
out on samples of boron doped polycrystalline silicon focusing on the 20ºC to 74ºC
temperature range. Rayleigh surface acoustic wave (SAW) and the longitudinal
lateral wave velocities were measured allowing the determination of the effective
elastic constants 11 C and 44 C of the material. The Young’s modulus was found to
change very little from about 150 GPa in the studied temperature range. On the other
hand, the bulk modulus showed a linear decrease from about 124 GPa at 20ºC to
about 112 GPa at 74ºC.
Elastic properties of a (100) oriented single crystal of the ternary semiconductor alloy
InAs0.91Sb0.09 are also reported in this work. This material has become an important
focus in the development of optoelectronic devices which operate in the long
wavelength transmission window of the atmosphere. SBS was used to measure the
angular dependence of the Rayleigh surface acoustic wave (SAW), pseudo surface
acoustic wave (PSAW) and the longitudinal lateral wave speeds as a function of
direction in the (100) surface to determine the room temperature values of the elastic
constants 11 C , 12 C and 44 C . To our knowledge, this is the first time that elastic
constants of InAs0.91Sb0.09 are reported using the SBS or any other technique.