High quantum efficiency II–VI photodetectors for the blue and blue-violet spectral range

We have fabricated II–VI wide gap hetero PIN photodiodes made of ZnMgSSe with excellent structural and interface quality and with a high external quantum efficiency of about 60%, which is close to the theoretical limit. The internal quantum efficiency reaches peak values of more than 80%. The onset of the sensitivity is very sharp, leading to a quantum efficiency less than 10−4 at wavelength 60 nm below the band gap. Using the wide range of energy gaps from 2.68 to 3.1 eV, it is possible to fabricate wavelength selective detectors if the energy gap of the top p-type layer is chosen slightly higher than that of the intrinsic zone. The dark current is below 0.1 pA/mm2. In the low signal limit, the noise equivalent power can be estimated to be below 10−15 WHz/mm2 at the peak external quantum efficiency, surpassing ultraviolet optimized Si detectors.