Heterojunction Devices Fabricated from Sprayed n -Type Ga 2 O 3 , Combined with Sputtered p -Type NiO and Cu 2 O.

This work reports on the properties of heterojunctions consisting of n -type Ga 2 O 3 layers, deposited using ultrasonic spray pyrolysis at high temperature from water-based solution, combined with p -type NiO and Cu 2 O counterparts, deposited by radio frequency and reactive, direct-current magnetron sputtering, respectively. After a comprehensive investigation of the properties of the single layers, the fabricated junctions on indium tin oxide (ITO)-coated glass showed high rectification, with an open circuit voltage of 940 mV for Ga 2 O 3 /Cu 2 O and 220 mV for Ga 2 O 3 /NiO under simulated solar illumination. This demonstrates in praxis the favorable band alignment between the sprayed Ga 2 O 3 and Cu 2 O, with small conduction band offset, and the large offsets anticipated for both energy bands in the case of Ga 2 O 3 /NiO. Large differences in the ideality factors between the two types of heterojunctions were observed, suggestive of distinctive properties of the heterointerface. Further, it is shown that the interface between the high-temperature-deposited Ga 2 O 3 and the ITO contact does not impede electron transport, opening new possibilities for the design of solar cell and optoelectronic device architectures.