Entropy-driven metastabilities in defects in semiconductors

Several defects are known to have metastable configurations that can be accessed by charge-state change, optical excitation, or heating followed by rapid cooling. Typically, each configuration is stable over a broad temperature range and can be studied by spectroscopic techniques. In this Letter, we report the observation of a novel metastability: A configuration change occurs spontaneously and abruptly at a critical temperature, giving rise to a discontinuous, deep-level transient spectrum. We propose that this phenomenon is a manifestation of entropy variations in the configurational space. © 1988 The American Physical Society.