A light-emitting device with a protection layer for Zn inter-diffusion and a process to form the device are described. The device of the invention provides an active layer containing aluminum (Al) as a group III element, typically AlGaInAs, and protection layers containing silicon (Si) to prevent the inter-diffusion of zing (Zn) atoms contained in p-type layers surrounding the active layer. One of protection layers is put between the active layer and the p-type cladding layer, while, the other of protection layers is disposed between the active layer and the p-type burying layer.