Aluminum doped silicon carbide thin films prepared by hot-wire CVD: Influence of the substrate temperature on material properties

Successful p-type doping of mu c-SiC:H with Al introduced from trimethylaluminum has been already demonstrated. In this work we focus on the influence of substrate temperature (T-s =300-390 degrees C) on the Al-doping. As T-s is reduced from 390 degrees C to 300 degrees C, the crystallinity decreases from 75% to 55% and the dark conductivity sigma(D) decreases first by about three orders of magnitude before increasing again at T-s = 300 degrees C. Both microstructure, as determined from Raman spectroscopy, and optical absorption are little affected by the change in T-s. Upon annealing at 450 degrees C in vacuum, sigma(D) increases typically by two orders of magnitude up to 10(-4) S/cm, which is explained by dopant activation as a result of hydrogen desorption. It is concluded that a process temperature >350 degrees C is needed to obtain effective Al-doping for p-type mu c-SiC:H thin films. (C) 2011 Elsevier B.V. All rights reserved.