Intensity-dependent energy and line shape variation of donor–acceptor-pair bands in ZnSe:N at different compensation levels

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Abstract
We show that energy position and line shape of donor–acceptor‐pair luminescence bands in ZnSe:N/GaAs epilayers depend very sensitively on excitation density and compensation. A continuous development from structureless red‐shifted broad to well structured donor–acceptor‐pair (DAP) bands is observed for increasing excitation density. The red shift is explained by the fluctuating potential affecting the bands and impurity levels and is caused by random distribution of charged impurities in highly compensated samples. The shift is reduced when these charge fluctuations are diminished due to an increasing number of impurities being neutralized via light‐induced carrier excitation. These effects have not been taken into account in previous work concerning doped II‐VI materials; however, they have to be considered when evaluating the frequently used hypothesis of a deep donor in ZnSe:N as an explanation of low‐energy broadband DAP emission. The influence of band fluctuations on the behavior of the DAP luminescence and excitation spectra is qualitatively discussed.

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