Gallium(III) selenide (Ga2Se3) is a chemical compound. It has a defect sphalerite (cubic form of ZnS) structure. It is a p-type semiconductor 
It can be formed by union of the elements. It hydrolyses slowly in water and quickly in mineral acids to form toxic hydrogen selenide gas. The reducing capabilities of the selenide ion make it vulnerable to oxidizing agents. Keep it away from bases.