Deep donors in Cd1-xZnxTe:Cl.

Abstract

Measurements of the persistent photoconductivity (PPC) and Hall effect in Cl-doped ${\mathrm{Cd}}_{1\mathrm{\ensuremath{-}}\mathit{x}}$${\mathrm{Zn}}_{\mathit{x}}$Te indicate that the Cl donors form several distinct deep DX states, consistent with recent calculations. For x=0.20 only one DX state is evident, with a deep binding energy ${\mathit{E}}_{\mathit{d}}$=0.22 eV; the PPC has a single annealing transition at ${\mathit{T}}_{\mathit{a}}$=130 K. For x=0.28 the PPC has two distinct transitions, at ${\mathit{T}}_{\mathit{b}}$=100 K and ${\mathit{T}}_{\mathit{a}}$=190 K. We propose a model in which the presence of a second metastable state ${\mathit{DX}}^{\ensuremath{'}}$ boosts ${\mathit{T}}_{\mathit{a}}$ significantly. For x=0.28 the ${\mathit{DX}}^{\ensuremath{'}}$ lies 0.23 eV below the conduction band, whereas the deepest binding energy is ${\mathit{E}}_{\mathit{d}}$=0.40 eV. The rapid increase of ${\mathit{E}}_{\mathit{d}}$ with x explains the difficulty of obtaining n-type ZnTe using Cl dopants. Nevertheless, these materials are interesting because DX centers with large ${\mathit{E}}_{\mathit{d}}$ and high ${\mathit{T}}_{\mathit{a}}$ are potentially useful in optoelectronic applications. \textcopyright{} 1996 The American Physical Society.