Ultraviolet-C Photodetector Fabricated Using Si-Doped n-AlGaN Nanorods Grown by MOCVD

Abstract

Aluminum gallium nitride (Al x Ga 1−x N) alloy films and nanostructures have attracted extensive research attention for ultraviolet (UV) and deep ultraviolet optoelectronic applications. However, the morphology-controlled growth of high-quality Al x Ga 1−x N quasi one-dimensional nanostructures has been limited by the complex multicomponent phase diagram and inhomogeneous composition distribution. Here, we demonstrated the growth of Si-doped ntype compositionally uniform Al 0.45 Ga 0.55 N nanorods employing a metal organic chemical vapor deposition (MOCVD) technique for the application in UV-C photodetectors. A two-step growth process, namely, growth of undoped GaN seeds and subsequent growth of n-AlGaN nanorods over GaN seeds, has been developed. Various characterization techniques have been used to study the crystalline quality, orientation, and optical properties of the realized nanorods. Field emission scanning electron microscopy revealed a uniform distribution of vertically aligned n-AlGaN nanorods over the GaN seeds. X-ray diffraction studies showed that the grown nanorods are preferentially (0002) oriented with hexagonal crystal structure. High-resolution transmission electron microscopy images indicated the nanorods are single crystalline in nature, without any significant crystalline defects and dislocations. Cathodoluminescence spectra of AlGaN nanorods displayed a strong band edge excitonic emission peak at 276 nm at 77 K and shifted to lower energy as the temperature increased to 300 K. The photocurrent current (I p ) of the fabricated photoconductive device was significantly higher in the UV region (250−276 nm) compared to the corresponding dark current. The photocurrent displayed a nonlinear power density (P)-dependent characteristics (I p ∝ P 0.64 ). The photoresponsivity and sensitivity of the fabricated photodetector were estimated to be ∼115 mA/W and ∼64%, respectively, in the UV-C region.

Unleashing the potential of molecular beam epitaxy grown AlGaN-based ultraviolet-spectrum nanowires devices

“…At −4 V, S has a value of 3.81 × 10 2 . The responsivity value, however, is still lower than previously reported AlGaN nanostructures 208,209 and AlGaN thin film photodetectors. 193,211 We emphasize that the device optimization has not been conducted and a relatively lower voltage was applied compared with that of AlGaN-based planar photodetectors.…”

Current advances in solar-blind photodetection technology: using Ga2O3 and AlGaN

“…In comparison to thin film/bulk devices, nanostructures have a high surface to volume ratio, which results in the higher generation of electron–hole pairs, leading to an increased photocurrent, and thus enhanced performances in the devices. Besides thin films, absorbing layers in the form of nanostructures, such as nanowires (NWs), 41,42,54 nanocolumns (NCs), 39 nanorods (NRs), 55–57 nanocones 40 and nanoflowers (NFs), 58 have been extensively studied for SB PDs. For instance, Kang et al 56 demonstrated the fabrication of a UV-C PD using Si-doped Al 0.45 Ga 0.55 N NRs having a length and diameter of 2.0 μm and 0.2 μm, respectively, grown on an undoped-GaN seeded Si substrate, as shown in Fig.…”

Deep-ultraviolet integrated photonic and optoelectronic devices: A prospect of the hybridization of group III–nitrides, III–oxides, and two-dimensional materials

“…Other than planar structures, Al x Ga 1−x N-based PDs constructed using lower-dimensional structures, such as nanowires and nanorods, have also received significant attention [518] . In 2017, Kang et al reported on a two-step growth process for single-crystalline silicon-doped Al 0.45 Ga 0.55 N nanorods as a solar-blind PD [519] .…”