Understanding the charge carrier transport characteristics at the graphene-GaN interface is of significant importance for the fabrication of efficient photoresponsive devices. Here, we report on the temperature dependent diode and photovoltaic characteristics of a graphene/n-GaN heterostructure based Schottky junction. The graphene/n-GaN heterojunction showed rectifying diode characteristics and photovoltaic action with photoresponsivity in the ultra-violet wavelength. The current-voltage characteristics of the graphene/n-GaN heterojunction device were investigated under dark and light illumination with changes in temperature. Under dark conditions, an increase in the forward bias current as well as saturation current was observed, and a decrease in the device ideality factor was obtained with an increase in temperature. Under illumination of light, a decrease in the open circuit voltage (Voc) and an increase in the short circuit current density (Jsc) was obtained with an increase in temperature. The increase in saturation current and carrier recombination with the increase in temperature leads to a reduction in Voc, while the photo-generated carrier increases in the heterojunction interface at higher temperatures contributing to the increase in Jsc. The observed temperature dependent device characteristics of the graphene/n-GaN heterojunction can be significant to understand the junction behavior and photovoltaic action.

We demonstrate the fabrication of a monolayer graphene/β-Ga 2 O 3 heterostructure and its interesting prospect of producing a suitable Schottky barrier potential for deep-ultraviolet (DUV) responsive photovoltaic device. The transient response behavior shows a faster response time for photovoltaic mode operation of the photodiode. The fast response at a zero bias is due to generation of photocurrent under an internal built-in field in the graphene/Ga 2 O 3 interface without any contribution from the trapped carriers. The fabricated device also shows an excellent photoresponsivity of 6.1 A W À1 with a slower response time at a low reverse bias voltage (À1.5 V). The high photoresponsivity at a bias voltage can be related to carrier multiplication due to carriers trapping/release process. Our findings show that the graphene/β-Ga 2 O 3 heterostructure can be significant for selfpowered/low power consuming DUV detector applications.

Here, we report on the large-area synthesis of hBN layer at a comparatively lower temperature using ammonia borane as precursor by microwave assisted surface wave plasma (MW-SWP) chemical vapour deposition (CVD). The solid precursor was sublimed inside the CVD chamber and decomposed to form plasma radicals, which allowed the growth of hBN layer at a lower temperature (∼500 °C). The growth of hBN on Cu catalyst and Si wafer was confirmed by X-ray photoelectron spectroscopy, ultraviolet absorption spectroscopy, Fourier-transform infrared spectroscopy and transmission electron microscopy analysis. The hBN film synthesized on Cu catalyst showed a sharp absorption peak at 276 nm wavelength corresponding to an optical band gap of ∼4.1 eV, owing to the incorporation of carbon and oxygen doping impurities. The reduction of optical band gap of the hBN film with impurity doping can be significant to tune its optoelectronic properties. Thus, the demonstrated MW-SWP-CVD process can be significant to synthesize hBN layers independent of the catalytic behaviour of the substrate, thereby opening enormous possibilities of transfer-free application for device fabrication and as transparent coating on various surfaces.

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Metal‐insulator‐semiconductor (MIS) based Schottky barrier diode (SBD) has significant importance for optoelectronics and other device applications. Here, we demonstrate the fabrication of a highly rectifying Schottky barrier diode (SBD) using a thin hexagonal boron nitride (hBN) interfacial layer in graphene and n‐type gallium nitride (n‐GaN) heterojunction. Significant reduction of reverse saturation current is obtained with the introduction of hBN layer in graphene/n‐GaN interface. The MIS based SBD shows excellent ultraviolet (UV) photoresponsivity with a light/dark ratio of ≈105 at a low reverse bias voltage (−1.5V). Temperature dependent current density‐voltage (J–V) characteristics of the graphene/hBN/n‐GaN heterojunction is investigated to elucidate the current transport behavior. The Schottky barrier height increased with increase in temperature from 0.77 to 0.98 eV in the temperature range of 298–373 K, respectively. The series resistance (RS) is also found to be temperature dependent, where RS decreased with increase in temperature. The understanding of graphene/hBN/n‐GaN heterojunction device characteristics can be significant for photodiode and switching device applications.