Ultraviolet light induced electrical hysteresis effect in graphene-GaN heterojunction

Abstract

Fabrication of a two- and three-dimensional (2D/3D) heterojunction device has attracted significant attention for developing high performance photodiodes, light emitting diodes, solar cells, and other electronic devices. Here, we reveal the effect of ultraviolet (UV) illumination on electrical hysteresis in a graphene/gallium nitride (GaN) vertical heterojunction Schottky device. A chemical vapor deposited graphene film was transferred onto a free-standing n-type GaN substrate for Schottky diode fabrication, where the interfacial states play a significant role in the occurrence of electrical hysteresis in diode characteristics. A fabricated graphene/GaN Schottky device free from electrical hysteresis under no illumination condition showed the appearance of hysteresis with the illumination of UV light. The residual impurities of graphene and the surface defects of the GaN act as trap sites for the photocarriers; as a result, interface dependent photoresponsivity was observed. Capacitance-voltage analysis also showed the effect of residual impurities on the space charge dependent capacitance and the occurrence of hysteresis due to interface traps of the graphene/GaN heterojunction. Our findings can be significant in understanding the highly sensitive graphene/GaN and other 2D/3D heterojunction interfaces by the UV illumination process for developing high performance devices.