A novel germanium doping method for fabrication of high-performance p-channel poly-Si/sub 1x/Ge/sub x/ TFT by excimer laser crystallization

In this letter, 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 (mu)m/2 (mu)m, 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 (mu)m/2 (mu)m. The poly-Si/sub 0.91/Ge/sub 0.09/ TFT exhibited a high-hole mobility of 112 cm/sup 2//V-s, while the hole mobility of the poly-Si counterpart was 73 cm/sup 2//V-s.