Ultrasensitive self-powered large area planar GaN UV-photodetector using reduced graphene oxide electrodes

Abstract

A simplistic design of a self-powered UV-photodetector device based on hybrid r-GO/GaN is demonstrated.Under zero bias, the fabricated hybrid photodetector shows a photosensivity of ∼ 85% while ohmic contact GaN photodetector with identical device structure exhibits only ∼5.3% photosensivity at 350 nm illumination (18 µW/cm 2 ). The responsivity and detectivity of the hybrid device were found to be 1.54 mA/W and 1.45×10 10 Jones (cm Hz ½ W −1 ), respectively at zero bias with fast response (60 ms), recovery time (267 ms) and excellent repeatability. Power density-dependent responsivity & detectivity revealed ultrasensitive behaviour under low light conditions. The source of observed self-powered effect in hybrid photodetector is attributed to the depletion region formed at the r-GO and GaN quasi-ohmic interface.The tremendous progress in gallium nitride (GaN) based light emitting diodes (LEDs), 1 laser diodes 2 , and other GaN based devices, namely, UV photodetector (PD) has attracted a great deal of interest from research community. 3 Being chemically inert and thermally stable, they are the most suitable for applications such as flame detection, secure space communication and ozone layer monitoring. 4,5 To match the requirements for such applications in remote and extreme environment, it is highly desirable for the UV devices to be ultrasensitive, with fast response and operate in self-powered mode. However, inherent high defect density associated with as-grown epitaxial GaN films limits its performance. 6The various schemes of metal-semiconductor (M-S) interfaces have been used to improve the UV-PDs device performance. The use of two different metal electrodes on n-GaN with modulating Schottky barrier height leads to a fast response speed but limited reverse saturation current density. 7 Earlier study has shown Schottky contact photodiode of Ni/GaN/Au with asymmetric interdigitated finger electrodes having a responsivity of 5 mA/W in self-powered mode at UV illumination. 8 Recently, Sun et al. have reported a high responsivity of 104 mA/W at zero bias voltage of interdigitated Schottky contact photodiode of Ni (80 nm) /GaN/Ti (20 nm) /Al (60 nm) device. 9 On the other hand, the use of highly transparent conductive electrodes (TCE) such as indium-tin-19 W. S. Hummers and R. E. Offeman, J. Am. Chem. Soc. 80, 1339 (1958).

Solution‐Processed Visible‐Blind Ultraviolet Photodetectors with Nanosecond Response Time and High Detectivity

“…Ultrafast, high‐sensitivity, visible‐blind UV photodetectors have broad applications in optical communications, environmental ozone hole monitoring, and combustion and radical detection . Compared to the mature UV photodetectors based on silicon, solid‐state UV photodetectors based on wide bandgap semiconductors, such as gallium nitride (GaN), silicon carbide (SiC), strontium titanate (SrTiO 3 ), etc., open new possibilities for UV radiation detection, as these semiconductor materials can be produced and used as “visible‐blind” or “solar‐blind” detectors that are not affected by visible light, which avoids the requirement of high‐cost filters as well as complicated optical system design and integration. However, these traditional inorganic semiconductors are generally deposited by slow, expensive, and high‐temperature processes .…”

Role of ZrO2 Passivation Layer Thickness in the Fabrication of High‐Responsivity GaN Ultraviolet Photodetectors

“…Under such circumstances, a viable solution for enhancing D * can be obtained by maximizing the value of responsivity via a controlled passivation of surface states in the GaN layer, as shown in Figure a. In Figure b, recently reported values of D * for several state‐of‐the‐art visible blind GaN UV PDs are plotted as a function of dark current along with our results. Note that the value of D * measured for sample B is higher or comparable to the values reported in the literature irrespective of its large dark current.…”

“…Another important figure of merit of PDs is the specific detectivity ( D *), which corresponds to their ability to detect the weakest signal. Recently, a few methods have been proposed by researchers for enhancing the value of D *, which is actually estimated by following the procedure given by Gong et al. To compare the values of D * of our devices with the recently reported state‐of‐the‐art values, we also followed the same procedure, and the estimated values of D * are plotted in Figure a.…”

Long‐Term, High‐Voltage, and High‐Temperature Stable Dual‐Mode, Low Dark Current Broadband Ultraviolet Photodetector Based on Solution‐Cast r‐GO on MBE‐Grown Highly Resistive GaN

“…The 2D material‐based devices can have a revolutionizing impact on technology covering from vacuum photodetection and photovoltaics to optical modulators and high speed data communication . Predominantly through vertical transport of photogenerated carriers, the hybrid structures allow us to overcome the inherent persistent photoconductivity (PPC), where photocurrent of the host material generally persists for a long duration even after the illumination is removed, generally observed in the compound III‐nitride semiconductor materials . Usually PPC occurs due to the presence of donor and acceptor states closer to the conduction band minimum (CBM) and valence band maximum (VBM), which provides a large number of electron and hole trap states in the host material, respectively.…”

“…In particular, GaN integrated with reduced‐graphene oxide (r‐GO) is a promising heterostructure for achieving improved device characteristics such as low dark current, high spectral responsivity, and high response speed . 2D r‐GO makes an optically active heterojunction with GaN.…”