Highly sensitive porous silicon based photodiode structures

Al/PS/c-Si photodiode structures were fabricated with a porous silicon (PS) layer of high porosity. Photosensitivity spectra, current–voltage (I–V) dependences at different temperatures, and electron beam induced current profiles were analyzed. Effects of annealing on the device characteristics were studied. The photosensitivity spectrum of the Al/PS/c-Si structures was found to be analogous to that of Al/c-Si structures. The photosensitivity value of as-prepared Al/PS/c-Si structures is 1.3 times that of an Al/c-Si Schottky diode in the wavelength range of 0.5–1.0 μm. The photosensitivity of the annealed structure strongly depends on the reverse bias; it increases by more than two orders of magnitude (up to 10 A/W) when the reverse bias increases from 0 to 5 V. The I–V dependences indicate that band bending on the sides of the PS/c-Si heterointerface are in opposite directions.