SILICON RADIATION DETECTOR

PURPOSE:To increase an applied voltage and obtain radiation having a good sensitivity and a high reliability, by separately forming an a-Si film having a small dark current conductivity from an a-Si film serving as a functional film of a hetero junction. CONSTITUTION:Two a-Si films 21 and 22 whose lower layer is a second conductive type of a low impurity concentration and whose upper layer is substantially neutral by doping an impurity are coated on a c-Si substrate 1 of a first conductive type. Then, electrodes 4 and 3 respectively in contact with the rear surface of the c-Si substrate 1 and the surface of the upper layer a-Si film 22 are formed. Thus, the lower layer a-Si film 21 in contact with the c-Si substrate 1 is the second conductive type of the low impurity concentration, for example, non-dope and serves as a functional film of a large light conductivity in which a hetero junction is formed. In the other hand, since the upper layer a-Si film 22 is substantially neutral by doping the impurity, a dark conductivity is minimized and a resistance becomes high and a leakage current is reduced. Thus, a good response to radiation is obtained.