High-detectivity solar-blind deep UV photodetectors based on cubic/monoclinic mixed-phase (InxGa1−x)2O3 thin films

Mixed-phase (InxGa1−x)2O3 films were fabricated by excessive doping of In in Ga2O3 and by controlling different precursor weight ratios of monoclinic Ga2O3 and cubic In2O3. X-ray diffraction and transmission spectra showed that excessive indium doping over the solubility of In in Ga2O3 causes phase separation and the formation of films in which monoclinic (InxGa1−x)2O3 (β-IGO) and cubic (InxGa1−x)2O3 (c-IGO) coexist. The (InxGa1−x)2O3 photodetector with a ratio of Ga2O3: In2O3 = 10: 1 is highly sensitive to solar-blind radiation with an ultralow dark current of 0.03 pA and a large I254 nm/Idark up to 2.53 × 107 under − 7 V bias. Under a bias of 10 V, the device has a high responsivity and detectivity of 0.97 A/W and 4.62 × 1014 Jones, respectively. The ultralow dark current is attributed to the interface states at the grain boundaries between β-IGO and c-IGO in the mixed-phase films, which can trap electrons and form potential barriers that inhibit carrier transport. Irradiation under 254 nm light generates electron-hole pairs in β-IGO and c-IGO, which are separated by internal electric fields. The holes are captured during migration by potential traps, causing continuous electron injection and sweep-out until the holes escape from the traps, resulting in a device with good performance. The proposed alloying method could be used to fabricate future photoelectric devices.