Effects of optical absorption on the quasi-Fermi level splitting at the emitter-base junction in npn heterojunction bipolar phototransistors

The effects of optical absorption in the quasi-neutral base region of npn heterojunction bipolar phototransistors on the extent of electron quasi-Fermi level splitting at the emitter-base heterojunction interface were studied. The increase in minority carrier concentration produced by optical generation in the base led to a decrease in the quasi-Fermi level splitting at the heterojunction interface which reduces the net electron injection into the base and emitter injection efficiency.