Luminescence Associated with Shallow Acceptor Centers in ZnTe

Abstract

The luminescence centers in ZnTe(Li) and ZnTe(P) have been studied from 2 to 300\ifmmode^\circ\else\textdegree\fi{}K, using photoexcitation and electron beam excitation. As-grown crystals of ZnTe(P) and ZnTe(Li) of comparable electrical properties exhibit similar luminescence spectra. An emission series starting at 2.33 eV (2\ifmmode^\circ\else\textdegree\fi{}K) present in both materials can be attributed to transitions from the conduction band to the un-ionized acceptor level. The response of ZnTe(Li) and ZnTe(P) to thermal treatments is different. Li can be removed from ZnTe(Li) by low-temperature (250\ifmmode^\circ\else\textdegree\fi{}C) firings for extended periods of time (8 days), and the associated emission peaks markedly diminish in intensity. The emission of ZnTe(P) is stable under this treatment. High-temperature, short-term firings (850\ifmmode^\circ\else\textdegree\fi{}C, 2 h) under maximum Zn overpressure produce different changes in the emission spectra and in the electrical properties of ZnTe(P) and ZnTe(Li). ZnTe(Li,Al) crystals exhibit a luminescence spectrum which indicates that interaction between Li and Al occurs.