Metalorganic molecular-beam epitaxy of ZnSe and ZnS

Abstract

The metalorganic molecular‐beam epitaxial growth of ZnSe and ZnS on (100) GaAs has been demonstrated and characterized. Diethylzinc and diethylselenide were used for the ZnSe growth, while for the ZnS growth both hydrogen sulfide and diethylsulfide (DES) were tested as sulfur sources. The dependence of the growth rate on various growth conditions was investigated to clarify the growth mechanism. When group VI alkyls were used as sources, pyrolysis in a cracking cell was required, unlike metalorganic chemical vapor deposition. Interesting differences in growth kinetics and in crystallinity between H₂S‐based and DES‐based ZnS have been found. Photoluminescence spectra of ZnSe layers measured at 4.2 K showed resolved exciton emissions. However, donor‐acceptor pair emission lines attributed to a Li acceptor (Li_Zn) were also observed. Smooth, monocrystalline ZnS layers could be grown at substrate temperatures above 250 °C by using cracked H₂S and DES, and above 150 °C by using uncracked H₂S. Photoluminescence spectra of ZnS layers at 74 K were dominated by unidentified blue emissions. These good results reflect the complete absence of a premature reaction.