Influence of Carbon Addition on the Electrical and Structural Properties of Phosphorus and Boron Doped Silicon Layers

Abstract

Phosphorus and boron doped polycrystalline silicon layers grown by chemical vapor deposition were additionally doped with carbon via the introduction of in the gas phase. Addition of carbon to n‐type and p‐type polycrystalline silicon gives rise to characteristic differences in resistivity vs. input pressures, at least at small input pressures of . The difference in resistivity can be explained by a donor activity of carbon or silicon‐carbon complexes or by an asymmetrical energy distribution of grain boundary traps, both at the grain boundaries. It is also shown that the addition of carbon has a strong influence on the morphology of the growing silicon layer. With increasing values of , the size of the grains in the layer decreases, under certain circumstances even amorphous silicon is formed, and this effect is stronger at the lowest temperatures. The decomposition kinetics of has also been discussed. It is concluded that at high input pressures of the deposition rate of carbon is gas phase diffusion controlled. At lower values and temperatures above 850°C, the formation of Si‐C nuclei is rate‐limiting as far as the introduction of carbon is concerned.