Oxygen vacancy tuned Ohmic-Schottky conversion for enhanced performance in β-Ga2O3 solar-blind ultraviolet photodetectors

Abstract

β-Ga2O3 epitaxial thin films were deposited using laser molecular beam epitaxy technique and oxygen atmosphere in situ annealed in order to reduce the oxygen vacancy. Metal/semiconductor/metal structured photodetectors were fabricated using as-grown film and annealed film separately. Au/Ti electrodes were Ohmic contact with the as-grown films and Schottky contact with the annealed films. In compare with the Ohmic-type photodetector, the Schottky-type photodetector takes on lower dark current, higher photoresponse, and shorter switching time, which benefit from Schottky barrier controlling electron transport and the quantity of photogenerated carriers trapped by oxygen vacancy significant decreasing.

Self-powered hybrid humidity sensor and dual-band UV photodetector fabricated on back-contact photovoltaic cell

“…The constant 1 is related to the rapid change of the carrier concentration when the UV light is turned on/off, and 2 is related to carrier trapping and release due to the oxygen vacancy defects in the thin film [18]. [23]. The lower responsivity and longer response time of our Ga 2 O 3 PD should be mainly due to the number of oxygen vacancies defects.…”

“…Compared with the XRD spectra in Refs. [23,24], our Ga 2 O 3 film shows amorphous structure (Fig. 3b), and thus, it has more oxygen vacancies defects [25].…”

“…Previous reports indicate that the absence of oxygen vacancies leads to a high photocurrent/dark current ratio and a fast response while the photogenerated electrons and holes separate rapidly and then transfer toward the electrodes. Also, the slow decay is attributed to the oxygen-related hole-trap states at the surface to prevent charge-carrier recombination [23,24]. In addition, the measured responsivity can be increased by increasing the applied bias voltage.…”

“…To discuss the response time of the PDs, the curve in Fig. 7 was fitted by the following equation [22,23]:…”

Toward the understanding of annealing effects on (GaIn)2O3 films

“…As oxygen vacancy often introduces another component beyond the lattice oxygen component in the O 1s peak, we used two components that are fit to confirm the oxygen vacancy [15]. It is clear that the O 1s peak can be consistently fitted by two near components, centered at 529.6 (O I ) and 530.6 eV (O II ) which is related to O 2− on the lattice structure and oxygen vacancy, respectively [15]. The energy difference between O I and O II peaks for all films is about 1.0 eV.…”