Minority carrier properties of GaAs films grown by MOCVD on ZnSe-coated silicon

This paper concerns investigations of MOCVD growth of GaAs on silicon with ZnSe buffer layers and the measurement of the minority carrier diffusion length of the heteroepitaxially grown GaAs films. Work to date has emphasized development of procedures for MOCVD growth of (100) ZnSe onto (100) silicon wafers, and subsequent growth of GaAs films on ZnSe/Si substrates. In order to grow high quality single crystal GaAs with a (100) orientation, which is desirable for solar cells, one must grow single crystal (100) ZnSe onto silicon substrates. A process for growth of (100) ZnSe has been developed involving a two-step growth procedure at 450°C. Single crystal, (100) GaAs films have been grown onto the (100) ZnSe/Si substrates at 620°C that are adherent and specular. Minority carrier diffusion lengths for n-type GaAs films grown on ZnSe/Si substrates have been determined from photoresponse properties of Al/GaAs Schottky barriers. Diffusion lengths are currently on the order of 0.3 μm compared to 2.0 μm for GaAs films grown simultaneously by homoepitaxy on GaAs