Patent ID: 11721752

Abstract:
A semiconductor device includes a doped substrate and a seed layer in direct contact with the substrate. The seed layer includes a first seed sublayer having a first lattice structure. The first seed layer is doped with carbon. The seed layer further includes a second seed sublayer over the first see layer, wherein the second seed layer has a second lattice structure. The semiconductor device further includes a graded layer in direct contact with the seed layer. The graded layer includes a first graded sublayer including AlGaN having a first Al:Ga ratio; a second graded sublayer including AlGaN having a second Al:Ga ratio different from the first Al:Ga ratio; and a third graded sublayer over including AlGaN having a third Al:Ga ratio different from the second Al:Ga ratio. The semiconductor device includes a channel layer over the graded layer. The semiconductor device includes an active layer over the channel layer.