Ultrasonic Study of Dynamic Behavior of Jahn-Teller Distorted Cr²⁺ Centers in GaAs

Abstract

The relaxation time, τ, for the reorientation of the ⟨100⟩-tetragonal Jahn-Teller distorted Cr²⁺ centers in GaAs was measured by ultrasonic method as a function of temperature. The center yielding the ultrasonic attenuation was identified to be Cr²⁺, based on the observed selection rule for the acoustic modes. The temperature dependence of 1⁄τ indicates that the relaxation in the temperature range below 20 K is ascribed not to the thermal activation process over the Jahn-Teller barrier but to the phonon-assisted tunnelings.