Selenium-related luminescent centers in metalorganic chemical-vapor-phase deposition grown ZnSe epilayers on GaAs

ZnSe epilayers were grown on a (001) GaAs substrate by metalorganic chemica l-vapor-phase deposition. An interruption of the Zn source (i.e., Se passiv ation) was purposely introduced during the growth. The optical properties o f the epilayers grown were studied by photoluminescence (PL) spectroscopy. We show that Se passivation during the growth interruption introduces lumin escent centers in the epilayers. Evidence of this assignment comes from the characteristic temperature and excitation wavelength dependence of the PL spectra, which are distinctly different from those of commonly observed dee p-level emissions associated with the so-called self-activated centers. Mor eover, the PL peak energy of the centers depends strongly on the coverage o f Se: the longer the time or the higher the flow rate of the Se precursor u sed for the passivation, the lower the energy of its PL peak. The possible origin of this luminescence is discussed. (C) 2001 American Institute of Ph ysics.