Entropy-Driven Metastabilities in Defects in Semiconductors

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Abstract
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.