Ageing mediated silicon suboxide interlayer growth in porous silicon: p-Si heterostructured metal-semiconductor-metal device for enhanced UV-visible photodetection

Abstract

Present work reports development of silicon oxide within metal-semiconductor-metal Schottky contact photodiode from Al: porous silicon (PS):p-Si heterojunction mediated by ageing to investigate its effect on its light sensing property. Oxide layer formation is achieved by auto-ageing. Formation of silicon suboxide (SiOx, x≤2) layers on PS:p-Si surface in aged heterostructure is confirmed from elemental energy dispersive X-ray analyses. X-ray diffraction patterns of as-prepared and aged heterostructure show broadening of strong (400) reflection peak compared to that of bare p-Si one due to nanocrystallite formation. PS crystallite size is found to be ∼45 nm. Raman spectra of as-prepared and aged heterostructure for an excitation wavelength of 633 nm show intense, broad and asymmetric peak at 519 cm−1 along with c-Si related peak at 522 cm−1. Photoluminescence spectra of as-prepared heterostructure shows red shift of ∼15 nm of the strong characteristic emission peak from 590 to 605 nm for increasing excitation wavelengths in the range of 275–400 nm. Aged heterostructure for fixed excitation wavelength of 275 nm shows strong characteristic emission peak at 590 nm along with weak emission peaks at 470 and 500 nm related to defect levels present in SiOx layers developed on PS surface. Ideality factor and Schottky barrier height for the aged device show enhancement of 12.4 and 0.15 eV respectively over the as-prepared one. The enhancement in maximum photo to dark current ratio of the aged device is 4.8, whereas maximum values of responsivity and external quantum efficiency improves up to 0.47 AW−1 and 145 % respectively for illumination wavelength of 400 nm for bias of -3 V. In contrast, however, the response and recovery times remain unchanged at 0.16 and 0.24 s respectively. These results suggest application potential of the device in the optoelectronic field particularly as an efficient ultraviolet-visible photo-detector.