Improved Process Stability and Light Detection in Phototransistors via Inverted MoS₂/a‐IGZO Heterojunction Integration

The integration of molybdenum disulfide (MoS 2 ) with other semiconductors to form heterojunction phototransistors demonstrates potential for optoelectronic applications due to their strong interaction with light and tunable bandgaps. Conventionally, bottom‐gate phototransistors based on MoS 2 and amorphous indium–gallium–zinc oxide (a‐IGZO) are fabricated by deposition of the a‐IGZO film on the gate dielectric, followed by deposition of the MoS 2 film, resulting in a MoS 2 /a‐IGZO heterojunction. In this study, an inverted MoS 2 /a‐IGZO (or denoted as a‐IGZO/MoS 2 ) heterojunction integration for bottom‐gate phototransistors, where the MoS 2 film is deposited on the gate dielectric first, followed by the deposition of the a‐IGZO film, is presented. This configuration is designed to enhance the processability and electrical properties of the phototransistor. Under visible light exposure with a low optical power density of 5.3 μW cm −2 , the a‐IGZO/MoS 2 heterojunction phototransistor demonstrates significantly improved photoresponsivity (1.6, 2.8, and 17 A W −1 at 635, 520, and 405 nm wavelengths, respectively) compared to the MoS 2 single‐channel phototransistor. Time‐dependent photoresponse measurements reveal that the a‐IGZO/MoS 2 heterojunction phototransistor responds more quickly to light changes and generates a tenfold‐greater photocurrent than that of the MoS 2 single‐channel phototransistor.