Optical Modulation of Current in GeSi n—n Heterojunctions

The I – V , characteristics, the C — V characteristics and the photocurrent spectra of GeSi n—n heterojunctions are consistent with a model in which a depletion region exists in each material. The depleted electrons reside in interface states which result from the mis‐match in lattice constants of the two materials. In this model, a notch exists in the valence band edge profile. Optically generated holes are trapped in the notch and the trapped holes modulate the device. The quantum efficiency of such a device compares favorably with that of a Si p—n homojunction.