US Patent 9608075 III-nitride semiconductor device with doped epi structures

A compound semiconductor device includes a first III-nitride buffer layer doped with carbon and/or iron, a second III-nitride buffer layer above the first III-nitride buffer layer and doped with carbon and/or iron, a first III-nitride device layer above the second III-nitride buffer layer, and a second III-nitride device layer above the first III-nitride device layer and having a different band gap than the first III-nitride device layer. A two-dimensional charge carrier gas arises along an interface between the first and second III-nitride device layers. The first III-nitride buffer layer has an average doping concentration of carbon and/or iron which is greater than that of the second III-nitride buffer layer. The second III-nitride buffer layer has an average doping concentration of carbon and/or iron which is comparable to or greater than that of the first III-nitride device layer. A method of manufacturing the compound semiconductor device is described.