Photo sensing property of nanostructured CdS-porous silicon (PS):p-Si based MSM hetero-structure

Abstract

Present work reports light sensing property of metal–semiconductor–metal device based on nanostructured CdS-PS:p-Si hetero-structure. PS with thickness of\u2009~\u20091500\xa0nm is prepared on p-Si (100) oriented wafer using electrochemical anodization method. Thin nanostructured n-CdS layer of\u2009~\u2009170\xa0nm is deposited on PS:p-Si substrate by vacuum evaporation. FESEM observation confirms growth of hierarchical flower like CdS nanostructure on PS:p-Si substrate. UV–Vis absorption spectrum gives bandgap of CdS nanostructure to be 2.6\xa0eV. Reflectance measurement of CdS-PS:p-Si hetero-structure shows multiple interference pattern within the spectral range of 200–800\xa0nm, with remarkable blue shift of the pattern compared to that of PS:p-Si structure. Photoluminescence study of the hetero-structure reveals presence of various luminescence bands peaked at\u2009~\u2009450, 460, 468, 482, 560, and 590\xa0nm. Dark current (Id) analysis shows low leakage current\u2009~\u200932 nA at −\u20092\xa0V with ideality factor (n) and reverse saturation current (Is) values of 1.57 and 0.2 nA respectively. Spectral response of the hetero-structure at a bias voltage of −\u20092\xa0V and irradiation wavelength of 400\xa0nm shows maximum responsivity (Rλ) value of\u2009~\u20090.6 AW−1 and external quantum efficiency of\u2009~\u2009180%. Response and recovery times of the device are\u2009~\u2009160 and\u2009~\u2009350\xa0ms respectively. The prepared hetero-structure has been compared with other silicon based optoelectronic switching devices to find suitability of an alternate choice.