Characteristics of hydrogenated amorphous silicon thin-film transistor

Abstract

The effects of N2 plasma interface treatment and atmospheric pressure chemical vapor deposition (APCVD) silicon dioxide (SiO2) gate insulator were investigated for the performance and the stability of hydrogenated amorphous silicon (a-Si:H) thin-film transistors (TFTs). To improve an a-Si:H/SiO2 interface, the N2 plasma treatment was carried out on the SiO2 surface. As a result, both the threshold voltage and subthreshold voltage swing were decreased remarkably. The high performance of a-Si:H TFTs was achieved with a field-effect mobility of 1.27 cm2/V s, threshold voltage of 3.5 V, and subthreshold voltage swing of 0.4 V/decade. For both positive and negative gate bias stresses, the threshold voltage was shifted in the positive direction and was dominated by the defect creation near the a-Si:H/SiO2 interface. There was little charge trapping into the APCVD SiO2 gate insulator. For the positive gate bias and time stress, the threshold voltage shifts were smaller than those of the conventional a-Si:H TFTs with the a-Si:H/SiNX interface.