Compensation mechanisms in ZnSe:N and codoped ZnSe:N:Cl

Abstract

Codoping experiments in ZnSe with Cl and N have been performed and the photoluminescence as well as the carrier concentrations have been studied to investigate the reason for compensation in ZnSe:N. Evidence could be given that not crystalline defects but rather potential fluctuations cause the often observed redshifted and broadened donor-acceptor-pair band in compensated layers. In addition, a quantitative study on these potential fluctuations could be performed by varying the chlorine concentration in $p$-type doped ZnSe:N:Cl. It has been shown that a chlorine concentration of $6\ifmmode\times\else\texttimes\fi{}{10}^{17}{\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$ in the codoped layers already causes a shift of the main donor-acceptor-pair band emission energy of about 120 meV. By investigating the photoluminescence spectra of samples with different chlorine concentrations, a relation between the amount of ionized impurities and the redshift in emission energy has been given.