Abstract

The defect centers responsible for the deep level emission commonly seen in the photoluminescence (PL) spectra of high purity VPE ZnSe have been studied. The ZnSe layers examined were heteroepitaxially deposited on GaAs by chemical vapor deposition, with palladium diffused hydrogen as the carrier gas. Under low excitation conditions, the 1.94, 2.2 and 2.7 eV emissions are usually observed at 77 K. A large dependence of the relative magnitudes of the observed PL bands upon crystal growth conditions was noted. For example, the free to bound emission at 2.7 eV was found to peak in intensity at a substrate growth temperature of 730 °C. For those samples whose free to bound emission at 2.7 eV predominates, hole traps at E_v+0.09 and E_v+0.13 eV have been observed by optical deep level transient spectroscopy (ODLTS). For these centers, concentrations as high as 2x10¹⁵ cm⁻³ have been measured. The origin of the two deeper emissions is not as clear, since the defect center responsible has not been detected by ODLTS. However, a potentially responsible defect level (at E_v+ 0.5 eV) has been observed by steady state photocapacitance at 77 K.

© 1984 Optical Society of America