Influence of high-k La2O3 interfacial oxide layer on the performance of GaN based Schottky barrier ultraviolet-B and A photodetection sensors

Abstract

GaN based metal-semiconductor-metal (MSM) type Schottky heterojunction-based ultraviolet (UV) photodetectors (PDs) have already proven as an efficient candidate for photodetection applications. However, in real time applications, GaN based MSM type UV PD device display higher dark current, weak signal detection and required external bias are seriously limiting their usage. Therefore, self-powered interdigitated electrode type Cr/Cu/La₂O₃/GaN: MIS (metal-insulator-semiconductor) heterojunction visible blind UV PD has been fabricated and studied in UV-B and A region. The structure, morphology, chemical and optical parameters of La₂O₃ films were evaluated using GIXRD, AFM, XPS and UV–Vis techniques, respectively. The reported interdigitated Cr/Cu/La₂O₃/GaN: MIS UV PD device yielded a higher Schottky barrier height (SBH) of 0.95 eV (dark) and 0.89 eV (360 nm) indicating the formation of higher potential barrier. At an applied bias of 0 V, the fabricated GaN MIS PD yielded an UV to visible rejection ratio (R₃₆₀/R₄₀₀) of 1.62 × 10². In UV-A region (at 0 V of 360 nm), the fabricated Cr/Cu/La₂O₃/GaN: MIS UV PD device exhibited a peak responsivity of 28.9 mAW⁻¹, D∗ of 3.57 × 10¹² Jones and EQE of 19.2 %. On the other hand, in UV-B region (at 0 V of 310 nm) the MIS UV PD device exhibited a peak responsivity of 34.4 mAW⁻¹, D∗ of 4.2 × 10¹² Jones and EQE of 22.7 %. During 360 nm illumination (at 0 V), the temporal response measurements of GaN UV PD device yielded the best rise/fall times of 70 ms/141 ms. This work validates the fact that the high-k La₂O₃ thin film as an interfacial oxide layer at the metal/GaN interface provides a novel solution for the photo detection field in the self-powered mode i.e., without any external bias.