It has been said that when manufacturing negative charge photoreceptor drum using high frequency plasma CVD, doping V-group element to carrier blocking layer has been considered necessary. However, by investigating the influence of impurity-doping on the characteristics of a photoreceptor drum, we found that it is possible to manufacture a negative charge a-Si photoreceptor drum without doping. We've confirmed that the electric potential characteristics and reliability of a negative charge a-Si photoreceptor drum are almost the same as a existing positive charge a-Si photoreceptor drum.In addition, the fact that potential drop by erase light of longer wavelength is smaller at a negative charge a-Si photoreceptor drum shows the possibility for developing a high charge type a-Si drum for use with near infrared light.