Improvement of Thick a-Si Radiation Detectors by Field Profile Tailoring

Application of thick ({approximately}50 {mu}m) a-Si p-i-n diodes as a direct radiation detector for minimum ionizing particles is hampered by the need to apply large bias voltages in order fully to deplete the detecting intrinsic layer, which typically contains 5 {minus} 10 {times} 10{sup 14} ionizable dangling bonds per CM{sup 3}. By insertion of thin p-type layers at intervals within the intrinsic layer, the required depletion voltage can be reduced by a factor of at least 1/(n+l) where n is the number of layers inserted. This principle is demonstrated for devices approximately 12{mu}m in thickness. It is shown that electron losses within the p type layer can be kept to minimum by choice of a low doping concentration for the introduced players.