Amplification of Total-Reflection-Mode Surface Phonons in n-Type InSb Films

Abstract

Acoustic waves can be propagated along the boundary of an elastic half-space [1]. The surface phonons are the quanta of elastic waves that satisfy the proper boundary condition on solid surfaces. In an elastic medium with a stress-free plane boundary, the waves are reflected on the boundary and the electrons localized in the surface region can be affected by the reflection of waves. The total-reflection (TR) mode due to the localized nature of wave functions in the vicinity of the solid surface becomes important when the sound velocity of propagation c lies between the transverse sound velocity ct and the longitudinal sound velocity cℓ [1]. It has been shown that the effect of nonparabolicity on amplification of surface phonons in n-type InSb becomes considerably important for the Rayleigh waves [2]. In this paper, we investigate the amplification characteristics of TR-mode surface phonons in n-type InSb films using the quantum mechanical treatment in the GHz region such that qℓ > 1, where q is the wave number of surface phonons and ℓ is the mean free path of electrons. The energy band structure of semiconductors is assumed to be nonparabolic. Both deformation-potential and piezoelectric couplings are considered in our numerical calculations.