Modelling the photoresponse of heterojunction bipolar transistors

An analytic model, which solves for the electrical and photogenerated currents in the emitter, base and collector of an HBT, is presented. Self aligned and non self-aligned devices, which have different empirical characteristics, are discussed. In the case of abrupt junctions, the model provides a correction term for the boundary conditions that account for band discontinuities. Experimental and theoretical results relating to the characteristics of the illuminated device given.