Characterization and Optimization of Transparent and Conductive ITO Films Deposited on n and p-types Silicon Substrates

Abstract

The characteristics of enhanced transparent and conductive indium tin oxide (ITO) films on n-type and p-type Si substrates grown by radio frequency (RF) magnetron sputtering were investigated.  The structural, optical and electrical properties of the films after annealing at different temperatures ranging from 300°C to 600°C in air were studied. X-ray diffraction (XRD) analysis reveals an amorphous structure for the as-deposited films of both the n-type and p-type Si. The annealed films exhibited a polycrystalline nature with preferential peaks orientation along (222) and (400) crystalline directions. Atomic force microscope (AFM) results indicate smooth surface morphology with increasing roughness as the annealing temperature increases. The surface roughness of the ITO films on the  p-type Si was high (6.65 nm) at 500°C and very good microstructures on both Si types were obtained at 500°C. Optical transmittance is enhanced from 89.1 % for the as-deposited film to 95.7 % for film annealed at 500°C in the visible range. ITO films on n-type and p-type Si demonstrate a substantial reduction in their electrical resistivity and sheet resistance with increasing annealing temperature. The ITO/p-Si structure exhibits a low resistivity of 2.45 × 10-5 ?-cm compared to 7.46 × 10-5 ?-cm for ITO/n-Si structure. The films performance showed a figure of merit of 14.68 × 10-3 ?-1 for ITO/n-type Si and 44.74 × 10-3 ?-1 for ITO/p-type at 500°C indicating that the optimized ITO films on p-type Si can be a promising ITO/p-Si heterojunction for silicon solar cells.