Performance evaluation of polycrystalline Si_1−xGe_x thin-film transistors fabricated by continuous-wave laser lateral crystallization on glass substrates

Abstract

This study was aimed at elucidating the performance of continuous-wave laser lateral-crystallized (CLC) polycrystalline Si1-xGex (poly-Si1-xGex) thin-film transistors (TFTs). The transfer characteristics of the n-ch CLC poly-Si1-xGex TFTs (x = 0, 0.05, 0.1, and 0.3) exhibited a positive shift in the threshold voltage (Vth) with increasing Ge content. Furthermore, the off-current in the p-ch CLC poly-Si0.9Ge0.1 TFTs decreased with decreasing film thickness. These properties of the CLC poly-Si1-xGex TFTs can be attributed to the generation of acceptors and increment of gate SiO2/poly-Si1-xGex interface charge state with increasing Ge content. Generation of acceptors was also supported by Hall effect measurements. In addition, the thermal stability of acceptors up to 700 ℃ was elucidated through Hall effect measurements and TFT performance evaluations. Furthermore, we examined the origins of these acceptors. This experiment highlighted the sensitivity of Si1-xGex to Ge incorporation, even in small amounts.