UV photodetectors and field-effect transistors based on $\beta$-Ga$_2$O$_3$ nanomembranes produced by ion-beam-assisted exfoliation

Abstract

$\beta$-Ga$_{2}$O$_{3}$ nanomembranes, obtained by ion-beam-assisted exfoliation, are used in the fabrication of simple metal-semiconductor-metal (MSM) structures, that are tested as photodetectors (PD) and field-effect transistors (FET). Ti/Au contacts to the membrane are found to be rectifying. However, through thermal treatment in a nitrogen atmosphere for one minute at 500 {\deg}C, it is possible to modify this junction to have an ohmic behavior. An MSM PD is studied, reaching a high responsivity of 2.6$\times$10$^{4}$ A/W and a detectivity of 2.4$\times$10$^{14}$ Jones, under 245 nm wavelength illumination, and an applied voltage of 40 V. In order to better understand the behavior of the two junctions, in particular the iono/photocurrent mechanisms, an ion microprobe system is used to assess the response of these PD when excitation is localized in the different regions of the device. Finally, a depletion-mode FET is obtained, with an on/off current ratio of 7.7$\times$10$^{7}$ in the linear regime, at a drain-to-source voltage of 5 V, and with a threshold voltage around $-$3 V. The success in obtaining FET, and most notably, MSM photodetectors, while using a simple device structure, indicates a great potential of the nanomembranes produced by ion-beam-assisted exfoliation for the development of high-performance devices.