ZnGeN2, one of the II–IV–N2 compounds, has been grown directly on r-plane sapphire by remote-plasma enhanced metalorganic vapor phase epitaxy. Single crystalline ZnGeN2 was obtained at growth temperature of 775 °C. Epitaxial relationship is ZnGeN2(010)/α-Al2O3(10–12), ZnGeN2[100] ∥α-Al2O3[11–20], and ZnGeN2[001] ∥α-Al2O3[10–11]. Band structure of ZnGeN2 is direct transition type from absorption spectrum. From photoluminescence measurements, sharp emission peaks related to band-edge, were observed at around 3.3 eV. Band gap energy of ZnGeN2 is 3.3 eV at room temperature by considering absorption and photoluminescence spectrum together. Temperature dependence of band gap was estimated from the photoluminescence peak positions for the first time.