Amorphous InSnZnO Thin-Film Transistor Voltage-Mode Active Pixel Sensor Circuits for X-Ray Imagers
Mao-Hsun Cheng, Chumin Zhao, Hyunsoo Kim, and Jerzy Kanicki
Amorphous indium-tin-zinc oxide thin-film transistor (a-ITZO TFTs) has exhibited superior device characteristics such as sa high mobility (μ > 30 cm22/V?s), steep subthrehold slop (SS < 200 mV/dec), low off current (IOFF < 10-14 A), and less threshold voltage shift (ΔVTH < 0.5 V), so it is expected to be capable of fulfilling high-end active-matrix flat-panel displays (AMFPDs) and imagers (APFPIs).
For x-ray imagers, we investigate the performance of the a-ITZO TFT-based voltage-mode active pixel sensor (V-APS). First, we compare the characteristics of an organic photodiode (OPD) and an amorphous silicon p-i-n photodiode (a-Si p-i-n PD) which are employed as photodetectors for V-APS. Next, source follower (SF) and common source (CS) types V-APS are studied. Then, we evaluate the impact of applying different PDs on a-ITZO TFT SF V-APS whose voltage gain and charge-to-voltage conversion are calculated as well. Finally, ΔVTH of the a-ITZO TFT is also taken into consideration to observe the performance variation of the a-ITZO TFT SF V-APS.
