Reduction of dark current under reverse bias in a-Si:H p-i-n photodetectors

This paper presents the development of low dark current amorphous silicon (a-Si:H) based heterojunction photodiodes. A series of p-i-n and n-i-p structures have been deposited by plasma-enhanced chemical vapor deposition (PECVD). Junction properties and carrier transport are investigated in terms of dark and light current-voltage characteristics, time dependence of the dark current, and spectral photoresponse measurements. It is demonstrated that a thin (similar to4 nm) undoped a-SiC:H buffer layer introduced between the p and i layers reduces the leakage current and improves the diode ideality factor. A dark current density of similar to10 pA/cm(2) at reverse bias of I V was achieved for the n-i-p structure. Optimization of device design for further improvement of dark current and photoresponse is discussed.