Patent ID: 8669467

Claim:
A photovoltaic device, comprising: a heterojunction comprising a n-doped GaAs layer directly adjacent to a p + -doped AlGaAs layer; and an interface layer comprising a Group III-V compound semiconductor above the p + -doped AlGaAs layer, wherein recesses are formed in the p + -doped AlGaAs layer, wherein the p + -doped AlGaAs layer forms an absorber layer having a thickness less than 800 nm such that electric energy is created when photons are absorbed, wherein the doping density in the n-doped GaAs layer is lower than in the p + -doped AlGaAs layer such that electrons in the n-doped GaAs layer have a higher mobility than the mobility of holes in the p + -doped AlGaAs layer, and wherein the p + -doped AlGaAs layer comprises a plurality of p + -doped AlGaAs layers wherein each of the plurality of p + -doped AlGaAs layer comprises a different percentage of aluminum.