Electrical properties of in-situ phosphorus and boron doped polycrystalline SiGeC films

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Description/Abstract

The sheet resistance, effective carrier concentration and Hall mobility of in-situ boron and phosphorus doped polycrystalline SiGeC films are presented for carbon contents between 0 and 4%. Phosphorus and boron doping levels of 4E19 and 2E20 cm-3 were achieved for the n- and p-type layers respectively and remained largely unaffected by carbon content. The phosphorus doped films showed a dramatic increase in sheet resistivity and a corresponding drop in effective concentration and Hall mobility. In contrast, the boron doped layers showed only a minor increase in resistivity. This is attributed to interstitial carbon increasing the defect density and also shifting the defect energy levels at the grain boundaries towards the valence band. This causes an increase in the grain boundary energy barrier in n-type layers, but leaves the p-type layers largely unaffected.