Highly doped p-type nanocrystalline silicon thin films fabricated by low-frequency inductively coupled plasma without H2 dilution

Abstract

p-type nanocrystalline silicon thin films with a series of thicknesses were deposited on both glass and n-type (100) silicon wafer substrates through a low-frequency inductively coupled plasma. No H2 dilution was employed in the growth process. The structural and electric properties of nanocrystalline silicon films were investigated by XRD, Raman spectra, and a Hall effect measurement system. The XRD patterns show an obvious enhancement of the peak intensity with increasing thickness. The crystalline volume fraction of the films ranges from 83% to 87%, depending on the film thickness. The carrier concentration of the films is in the range of 8.1×1019/cm3 – 8.6×1019/cm3. The realization of high doping concentration of p-type nanocrystalline silicon films is related with high electron density (the order of 1011cm-3–1012cm-3) in the chamber. On the basis of these studies, simple structured solar cells, consisting of ZnO: Al thin film (80 nm)/highly doped p-type nanocrystalline silicon films with a series of thickness/n-type (100) silicon wafer substrates, were fabricated and used to assess the performance of p-type nanocrystalline silicon films. The conversion efficiency increases with decreasing the film thickness of p-type nanocrystalline silicon thin films and achieves the largest value of 8.2% when the thin film thickness is near 90 nm.