Patent ID: 7902571

Claim:
A III-V group compound semiconductor device, comprising: a semi-insulating substrate; and a buffer layer, an active layer, and a contact layer sequentially formed on the semi-insulating substrate, wherein the buffer layer comprises a plurality of layers, comprising: a p-type buffer layer comprising Al x Ga 1-x As (0.3≦x≦1, where x represents a mix crystal ratio of Al) as a bottom layer; and a layered part comprising a plurality of undoped GaAs/Al y Ga 1-y As hetero structures (0≦y≦0.3, where y represents a mix crystal ratio of Al) formed directly on the p-type Al x Ga 1-x As buffer layer, the p-type Al x Ga 1-x As buffer layer being formed between the semi-insulating substrate and the layered part, wherein an Nd product defined as a product of a film thickness of the p-type buffer layer and a p-type carrier concentration of the p-type buffer layer is within a range from 1×10 10 to 1×10 12 /cm 2 , wherein the p-type carrier concentration comprises a concentration of at least one of oxygen and a transition metal selected from the group consisting of Ti, Cr, Fe, Co, Ni, and Cu, and wherein the film thickness of the p-type buffer layer comprising Al x Ga 1-x As is 2 to 50 nm.