Journal of Semiconductors, Volume. 43, Issue 6, 062804(2022)

Vertical Schottky ultraviolet photodetector based on graphene and top–down fabricated GaN nanorod arrays

Xuemin Zhang1,2, Changling Yan1, Jinghang Yang1, Chao Pang1, Yunzhen Yue1, Chunhong Zeng1,2, and Baoshun Zhang2
Author Affiliations
  • 1State Key Laboratory on High Power Semiconductor Lasers, Changchun University of Science and Technology, Changchun 130022, China
  • 2Nanofabrication Facility, Suzhou Institute of Nano-Tech and Nano-Bionics, Chinese Academy of Sciences, Suzhou 215123, China
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    GaN has been widely used in the fabrication of ultraviolet photodetectors because of its outstanding properties. In this paper, we report a graphene–GaN nanorod heterostructure photodetector with fast photoresponse in the UV range. GaN nanorods were fabricated by a combination mode of dry etching and wet etching. Furthermore, a graphene–GaN nanorod heterostructure ultraviolet detector was fabricated and its photoelectric properties were measured. The device exhibits a fast photoresponse in the UV range. The rising time and falling time of the transient response were 13 and 8 ms, respectively. A high photovoltaic responsivity up to 13.9 A/W and external quantum efficiency up to 479% were realized at the UV range. The specific detectivity D* = 1.44 × 1010 Jones was obtained at –1 V bias in ambient conditions. The spectral response was measured and the highest response was observed at the 360 nm band.

    1. Introduction

    GaN has been widely used in the fabrication of ultraviolet photodetectors (UV PDs) because of its direct wide bandgap of 3.4 eV and excellent thermochemical stability[14]. Typical GaN PD is based on photoconductivity, p–n junction, and Schottky barrier[57]. A metal layer of about 5 nm is commonly used as the transparent conductive layer in GaN PD[8]. However, this translucent metal has a low transmittance (10% absorption per nanometer), which blocks large amounts of light and reduces photoresponsivity. Moreover, because of low carrier mobility and short carrier lifetime, the photosensitive area of GaN photodetectors is usually limited to about 0.1 mm2, which is detrimental to imaging applications[9]. Graphene has excellent electrical conductivity (extremely high carrier mobility) and outstanding photopermeability from UV to infrared (2.3% per layer of absorption)[1012]. Furthermore, graphene is a kind of semi–metal that can form a Schottky junction with GaN[13]. So it is expected to be a substitute for metal electrodes on GaN PD devices[14, 15]. In addition to the function of transparent conductive electrodes, graphene can be used as an effective current transmission channel[16]. At the graphene/GaN interface, the photo–generated carriers can be separated due to the built-in electric field. This type of carrier can migrate into graphene to produce a photocurrent[17]. Due to the high defect density and low conductivity, the performance of conventional GaN-based photodetectors has been partially limited by the efficiency of photocarrier collection. GaN nanowire (NW) arrays can provide larger average current densities of vertical devices[18, 19]. A high-quality GaN nonpolar surface can be obtained without substrate lattice mismatch restriction and the stress release problem of GaN devices can be solved[20]. At present, GaN or other nanowires are commonly grown directly from the substrate with the down–top mode by molecular beam epitaxy (MBE) or metal–organic chemical vapor deposition (MOCVD)[21, 22]. However, this method is not only expensive but it is also difficult to control the morphology of nanowires. Another way to overcome these drawbacks is a top–down fabrication, using standard photolithography and etching to compose nanowires on a homogeneous film[23, 24]. Vertically aligned semiconductor nanorods (NRs) have been demonstrated in this top–down approach. However, until now, there have been few studies involving graphene and GaN nanorods in photodetectors.

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    Xuemin Zhang, Changling Yan, Jinghang Yang, Chao Pang, Yunzhen Yue, Chunhong Zeng, Baoshun Zhang. Vertical Schottky ultraviolet photodetector based on graphene and top–down fabricated GaN nanorod arrays[J]. Journal of Semiconductors, 2022, 43(6): 062804

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    Paper Information

    Category: Articles

    Received: Nov. 9, 2021

    Accepted: --

    Published Online: Jun. 10, 2022

    The Author Email:

    DOI:10.1088/1674-4926/43/6/062804

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