Spectroscopy of the phosphorus impurity in ZnSe epitaxial layers grown by molecular-beam epitaxy

Abstract

Phosphorus-implanted and plasma-doped ZnSe epitaxial layers grown by molecular-beam epitaxy are studied through photoluminescence (PL), selective PL, and PL-excitation spectroscopies. We show that with an activation energy of $85\ifmmode\pm\else\textpm\fi{}1\mathrm{meV},$ the P-related shallow-acceptor level is the shallowest acceptor ever detected in ZnSe. The series of excited states of this acceptor reveals that it behaves like all substitutional acceptors. We thus identify it as being the simple ${\mathrm{P}}_{\mathrm{Se}}$ substitutional impurity. Its excitonic emission definitely occurs at 2.791 eV. Negligible P-related deep levels can be detected by PL. However, a line which is relatively strongly coupled to phonons is detected at 2.796 eV. This line arises from P-related defects involving P incorporated on other-than-Se-substitutional sites. Finally, the lack of conductivity of our ZnSe:P samples, which does not stem from deep defects, could be explained by an AX-like behavior of the P impurity.