A blue-violet-near-ultraviolet pin-photodiode with small dark current, high reliability and long lifetime. The pin-photodiode has a metallic n-electrode, a n-ZnSe single crystal substrate, an optionally added n-ZnSe buffer layer, an n-Zn1-xMgxSySe1-y layer, an i-Zn1-xMgxSySe1-y layer, a p-Zn1-xMgxSySe1-y layer, a p-(ZnTe/ZnSe)m SLE, a p-ZnTe contact layer, an optionally provided antireflection film and a metallic p-electrode. A blue-violet-near-ultraviolet avalanche photodiode with small dark current, high reliability and long lifetime. The avalanche photodiode has a metallic n-electrode, a n-ZnSe single crystal substrate, an optionally added n-ZnSe buffer layer, an n-Zn1-xMgxSySe1-y layer, an i-Zn1-xMgxSySe1-y layer, a p-Zn1-xMgxSySe1-y layer, a p-(ZnTe/ZnSe)m SLE, a p-ZnTe contact layer, an optionally provided antireflection film and a metallic p-electrode. Upper sides of the layered structure are etched into a mesa-shape and coated with insulating films.