The quantum efficiency of photo-charge generation in a-Se avalanche photodetectors

The quantum efficiency of photo-charge generation and avalanche multiplication in amorphous selenium (a-Se) photodetectors were measured over considerable ranges of photoexcitation wavelengths (420-600 nm) and electric fields (10-112.5 V/μm) for several different a-Se target thicknesses (8-35 μm). An avalanche multiplication factor of 1000 is shown for a 35 μm thick a-Se layer at an electric field of 98 V/μm. The experimental results on quantum efficiency can be explained by the Onsager theory of electron-hole pair dissociation in conjunction with an electric field-induced delocalization of states