Study of elastic properties of semiconductors by surface Brillouin scattering

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.