Extraction Technique for Flat Band Voltage Using Multi-Frequency C – V Characteristics in Amorphous InGaZnO Thin-Film-Transistors

An extraction technique for flat band voltage (V
_FB
) in an amorphous InGaZnO (a-IGZO) thin-film transistor (TFT) using the frequency-independent C - V relationship which is taken from the measured multi-frequency C - V characteristics, is proposed. The proposed method comprises the consideration of multiple physical parameters for accurate VFB extraction, including the sub-gap density of states, doping concentration, gate oxide capacitance, and series resistance. The method was verified by comparing both the measured current-voltage characteristics and the extracted V
_FB
value with the technology computer-aided design simulation results. Moreover, we confirmed the versatility of the method by extracting VFB from devices with different oxygen contents. The proposed physical-based technique showed better accuracy and compatibility with amorphous oxide semiconductor (AOS) TFTs compared with classical empirically based methods. We believe that our technique is useful for the experimental design and optimization of the gate metal-dielectric-AOS stack for highperformance AOS TFTs.