Below band‐gap photoresponse of In1−xGaxP‐GaAs heterojunctions

Below band‐gap photovoltaic response with a half‐power point at 1.31 eV is observed in p‐type In1−xGaxP on n‐type GaAs heterojunctions with {111} interfaces. This response is apparently due to photon‐assisted tunneling of carriers across the interfacial energy gap, which is smaller than the energy gaps of the constituent materials. The same mechanism can be employed in other heterojunctions with appropriate energy‐band lineups to obtain longer wavelength infrared response.