UV Photoconductivity of Lateral p+-PSi-n+ Diode

In this work, a diode of lateral p$^+$-PSi-n$^+$ structure is fabricated in order to remove the strong photoresponse of silicon substrate to incident light with the existing structure, {\it i.e}. metal-PSi-Si structure, and then the UV photoconductivity of porous silicon(PSi) itself is investigated. The silicon diaphragm is formed on n-type silicon wafer by bulk micromachining technology, and the PSi is grown on the silicon diaphragm by photoelectrochemical etching with an constant applied voltage. The intensity change of photon flux is carried out by variation of distance between UV source and fabricated device. In the current-voltage characteristics curve, two linear regions appear and the slopes of each region are varied with various photon fluxes of UV. As intensity of photon flux increases, the current density increases under UV illumination. The sensitivity of the lateral p$^+$-PSi-n$^+$ diode is 0.144 mA/$\mu$W. A simple physical model of the fabricated diode is presented, based on deep traps and double injection. The photoionization of the negatively charged traps by UV illumination is responsible for the photocurrent of the device. The energy band diagram for lateral p$^+$-PSi-n$^+$ diode is also presented. KCI Citation Count: 0