Endurable IGZO/SnSx/IGZO Heterojunction Phototransistor Arrays for Image Sensors

Abstract

Optoelectronic devices require stable operation to detect repetitive visual information. In this study, endurable arrays based on heterojunction phototransistors composed of indium–gallium–zinc oxide (IGZO) with a low dark current and tin sulfide (SnS_x) capable of absorbing visible light are developed for image sensors. The tandem structure of IGZO/SnS_x/IGZO (ISI) enables stable operation under repetitive exposure to visible light by improving the transport ability of the photoexcited carriers through mitigated trap sites and their separation into each IGZO layer. Additionally, the structure promotes recombination by confining the holes. Therefore, the optimal ISI phototransistors exhibit a photoresponsivity of 514.50 A/W and a detectivity of 1.31 × 10⁹ Jones under red light (635 nm) of 1 mW/mm² and endurable time-dependent photoresponse characteristics, including a slope value of 1.66 × 10^–11, without the persistent photoconductivity phenomenon under green light (532 nm) at a frequency of 50 mHz for over 4,000 s. Furthermore, image sensing characteristics of the 6 × 6 arrays based on ISI phototransistors for image sensors are demonstrated by sequentially applying “4” and “2” digit numbers. These technologies contribute to the development of endurable oxide-based optoelectronic devices and provide valuable perspectives on the utility of next-generation image sensors.