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

Present work reports light sensing property of metal–semiconductor–metal device based on nanostructured CdS-PS:p-Si hetero-structure. PS with thickness of ~ 1500 nm is prepared on p-Si (100) oriented wafer using electrochemical anodization method. Thin nanostructured n-CdS layer of ~ 170 nm 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 eV. Reflectance measurement of CdS-PS:p-Si hetero-structure shows multiple interference pattern within the spectral range of 200–800 nm, 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 ~ 450, 460, 468, 482, 560, and 590 nm. Dark current (I_d) analysis shows low leakage current ~ 32 nA at − 2 V with ideality factor (n) and reverse saturation current (I_s) values of 1.57 and 0.2 nA respectively. Spectral response of the hetero-structure at a bias voltage of − 2 V and irradiation wavelength of 400 nm shows maximum responsivity (R_λ) value of ~ 0.6 AW⁻¹ and external quantum efficiency of ~ 180%. Response and recovery times of the device are ~ 160 and ~ 350 ms respectively. The prepared hetero-structure has been compared with other silicon based optoelectronic switching devices to find suitability of an alternate choice.