N-TYPE DOPING IN PECVD A-SI1-XCX-H OBTAINED UNDER STARVING PLASMA CONDITION

In this work, we study the n-type doping, by ion implantation, of a-Si 1-xCx:H which is obtained by standard r.f. plasma enhanced chemical va por deposition (PECVD) in the so-called 'silane starving plasma' condi tion from silane (SIH4) and methane (CH4) gaseous mixtures. In previou s work, we have shown the importance of this condition to obtain, in a morphous films, a chemical and structural order similar to crystalline (c) SiC, which suggests that material obtained in this condition is a promising candidate to obtain efficient substitutional doping. So, in this work, we utilize the ion implantation of phosphorus and nitrogen to obtain n-type doping in PECVD a-Si1-xCx:H grown in and out of the 'silane starving plasma' condition. The results show that in fact, the 'silane starving plasma' condition improves the n-type doping efficie ncy of the films to levels close to those obtained in device quality a -Si:H, the lowest activation energy being 0.12 eV for a nitrogen doped sample which presents a dark conductivity of 2.10(-3) (Omega cm)(-1) at room temperature. Another important observation has been that for a ll samples, nitrogen doping is more efficient than phosphorus doping, specially for carbon rich samples. (C) 1998 Elsevier Science B.V. All rights reserved.