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We demonstrate a high figure-of-merit UV–C solar-blind photodetectors fabricated from polycrystalline beta-gallium oxide (β-Ga2O3) grown on n-Si substrates by plasma assisted molecular beam epitaxy (PAMBE). We developed film growth sequences for nucleation of Ga2O3 on (100) and (111) oriented Si substrates, and systematically investigate the influence of crucial growth parameters, namely substrate temperature, oxygen flow rate and plasma power on the functional properties of the photodetectors. The photodetectors show ultra-high responsivity of 837 A/W and fast ON/OFF time below 4ms observed under 248 nm illumination at –5V. In addition, they display strong rectifying properties and sharp cut-off below 280 nm with average responsivities between 10-80 A/W, detectivity on the order of 1010 Jones, and rise/fall times between 4 to 500 ms at –5V. High photoconductive gain is shown to likely be due to the mid-bandgap donor/acceptor defect levels, including oxygen vacancies in the form of self-trapped holes. We demonstrate that these defect levels can be modified by controlling the growth conditions, thereby, allowing for tailoring of the photodetector characteristics for specific applications. Our methodology represents a cost-effective solution over homoepitaxial approaches, with characteristics that meet or exceed those reported previously, offering new possibilities for on-wafer integration with Si electronics.

We are now all familiar with the bright blue, green and white LEDs that light up our electronic appliances; decorate our streets and buildings and illuminate airport runways. However, the ultimate performance of these nitride semiconductor based LEDs is limited by extended defects such as threading dislocations (TDs), partial dislocations (PDs) and stacking faults (SFs). If we want to develop LEDs to be an effective replacement for the light bulb, or have sufficient power to purify water; we need to eliminate these defects as they act as scattering centres for light and charge carriers and give rise to nonradiative recombination and to leakage currents, severely limiting device performance. The capability to rapidly detect and analyze TDs, PDs and SFs, with negligible sample preparation, represents a real step forward in the development of more efficient nitride-based semiconductor devices