Photoelectrical properties of nonuniform semiconductor under infrared laser radiation

Photoelectrical properties of nonuniform semiconductor under infrared laser radiation has been investigated theoretically and experimentally. It is shown that photoemission of hot carriers across the potential barrier and the crystal lattice heating are dominant mechanisms of the photovoltage formation in p-n and l-h junction when laser photon energy less than the semiconductor energy gap. Influence of aluminum arsenide mole fraction in GaAs/AlxGa1-xAs p-n heterojunction on CO2 laser radiation detection has been studied. It has been established that the photoresponse originating from the free carrier heating depends on the energy band discontinuities in heterojunction. GaAs/AlxGa1-xAs heterojunction with x less than or equal to0.2 is found to be more suitable for infrared detection compared to GaAs homojunction. In metal-semiconductor Schottky contact photoresponse demonstrates strongly nonlinear (superlinear) dependence on excitation intensity when photon energy is less than Schottky barrier height. We suppose that in this case the photosignal is caused by the multiphoton and multistep electron photoemission across the Schottky barrier.