Aluminum-doped, n-type ZnSe layers ranging in thickness from several thousand Angstroms to several microns were grown epitaxially on differently oriented p-type Ge substrates by a low temperature, low pressure organometallic chemical vapor deposition process. The surface morphology and photoluminescence spectra reveal differences between the ZnSe films grown on (100)Ge substrates and those grown on (111)Ge substrates. Photoluminescence spectra of the former films show strong band gap luminescence, whereas the latter films are characterized by a reduced band gap luminescence intensity and an enhanced intensity in the self-activated region.