Study of Ge embedded inside porous silicon for potential MSM photodetector

Purpose - The purpose of this paper is to describe a very low-cost way to prepare Ge nano/microstructures by means of filling the material inside porous silicon (PS) using a conventional and cost effective technique in which thermal evaporator with PS acts as patterned substrate. Also, the potential metal-semiconductor-metal (MSM) photodetector IV characteristics of the structure are demonstrated. Design/methodology/approach - PS was prepared by anodization of Si wafer in ethanoic hydrofluoric acid. The Ge layer was then deposited onto the PS by thermal evaporation. The process was completed by Ni metal deposition using thermal evaporator followed by metal annealing of 400 degrees C for 10 min. Structural analysis of the samples was performed using energy dispersive X-ray analysis (EDX), scanning electron microscope (SEM), X-ray diffraction (XRD) and Raman spectroscopy. Findings - A uniform circular network distribution of pores is observed with sizes estimation of 100 nm to 2.5 mu m by SEM. Also observed are clusters with near spherical shape clinging around the pores believed to be Ge or GeO2. The EDX spectrum suggests the presence of Ge or GeO2 on and inside the pore structure. Raman spectrum showed that good crystalline structure of the Ge can be produced inside the silicon pores. XRD showed the presence of a Ge phase with the diamond structure by (111), (220), and (400) reflections. Finally, current-voltage (I-V) measurement of the Si/Ge/PS MSM photodetector was carried out. It showed lower dark currents compared to control device of Si. The device showed enhanced current gain compared to conventional Si device which can be associated with the presence of Ge nanostructures in the PS. Originality/value - This paper shows that it is possible to grow Ge nano/microstructure on PS by using a simple and low-cost method of thermal evaporation and thermal annealing and demonstrates potential MSM photodetector IV characteristics from the device.