A novel germanium doping method for fabrication of high-performance p-channel poly-Si1-xGex TFT by excimer laser crystallization

A novel process for fabricating p-channel poly-Si/sub 1-x/Ge/sub x/ thin-film transistors (TFTs) with high-hole mobility was demonstrated. Germanium (Ge) atoms were incorporated into poly-Si by excimer laser irradiation of a-Si/sub 1-x/Ge/sub x//poly-Si double layer. For small size TFTs, especially when channel width/length (W/L) was less than 2 μm/2 μm, the hole mobility of poly-Si/sub 1-x/Ge/sub x/ TFTs was superior to that of poly-Si TFTs. It was inferred that the degree of mobility enhancement by Ge incorporation was beyond that of mobility degradation by defect trap generation when TFT size was shrunk to 2 μm/2 μm. The poly-Si/sub 0.91/Ge/sub 0.09/ TFT exhibited a high-hole mobility of 112 cm
²
/V-s, while the hole mobility of the poly-Si counterpart was 73 cm
²
/V-s.