Si-Ga2O3/p-GaN epitaxial heterostructure based self-powered and visible-blind UV photodetectors with fast and electrically tuneable response time
n-Ga2O3/p-GaN heterojunction based photodetector devices are fabricated on Si-doped (-201) \beta-Ga2O3 epitaxial layers grown by pulsed laser deposition (PLD) technique on p-type c-GaN/sapphire templates. These devices demonstrate the ability to act as highly efficient self-powered visible blind UV-photodetectors with fast response time. It has been found that the optimum performance of the detector in terms of its responsivity, detectivity and response time could be achieved by adjusting the Si doping level and the thickness of the Ga2O3 layer. Our best performing device showing the peak responsivity and detectivity of 56.8 mA/W and 3*10^12 Jones, respectively, is achieved for 660 nm thick Ga2O3 layer with Si-concentration of 8*10^18 cm^-3. Moreover, as low as a few nW of optical signal can be sensed by the detector. The response time of the detector is found to be only a few tens of nanoseconds, which highlights their potential for application in ultrafast detection of UV light. These devices also exhibit a slower component of photoresponse with a timescale of a few tens of milliseconds. Interestingly, the time-scale of the slower response can be prolongated by several orders of magnitude through enhancing the applied reverse bias. Such an electrical tuneability of the response time is highly desirable for neuromorphic device applications.