Highly Sensitive Ultraviolet Photodetector Based on an AlGaN/GaN HEMT with Graphene‐On‐p‐GaN Mesa Structure

Abstract

The advantageous role of 2D electron gas presence at the AlGaN/GaN interface attracts huge interest in the field of GaN‐based ultraviolet photodetector technology. However, the presence of high dark current deteriorates the photodetector performance by diminishing several figures of merit. In this work, enhanced figures of merit are demonstrated by employing interdigitated p‐GaN finger structure on the top of the AlGaN/GaN heterostructure. The commonly present high dark current in p‐GaN/AlGaN/GaN planar photodetector is largely reduced (from ≈µA to few pA) by etching the p‐GaN, excluding the electrode region. Furthermore, by using a graphene transparent electrode along with the p‐GaN interdigitated fingers on AlGaN/GaN heterostructure, ultraviolet photodetectors with superior sensitivity (3.55 × 106) and ultrahigh detectivity (1.91 × 1014 cm Hz1/2 W−1) are realized at 360 nm. A comparison of graphene/p‐GaN and Ni/Au/p‐GaN interdigitated fingers and planar p‐GaN (with interdigitated graphene contacts) all on AlGaN/GaN heterostructure allows to understand the dominant roles of electrode transparency and the heterojunction structure. The simple and high electron mobility transistor‐compatible fabrication process of UV detectors provides a unique application in the field of UV sensing technology.

High-Photosensitivity WSe2 Phototransistor with Electrically Self-Isolated C8-BTBT as a Light Absorption Layer

“…Recently, two-dimensional (2D) transition metal dichalcogenides (TMDs), such as MoS 2 , MoSe 2 , WS 2 , and WSe 2 , have attracted tremendous attention as next-generation semiconductors due to their fascinating electrical and optical properties. − The electrical properties of 2D TMD-based field effect transistors can be effectively and nondestructively tuned by coating various organic molecules on their surface due to surface charge-transfer doping or formation of heterostructures. − However, many previous reports found that this may result in an increase of both ON and OFF current, severely limiting the signal-to-noise ratio (SNR) when applied to photosensing applications (i.e., phototransistors). − An example of such an increase in OFF current after coating organic molecules on a 2D TMD-based transistor is shown in Figure S1. Therefore, the effective application of organic coatings on TMD-based phototransistors dictates that it is necessary to limit potential OFF current increases and act as a light absorption layer to improve the photosensitivity (i.e., SNR) of TMD-based phototransistors.…”

Self-Powered Broadband Photodetector Based on NiO/Si Heterojunction Incorporating Graphene Transparent Conducting Layer

“…Instead of single-band detectors, broadband photodetectors such as UV-visible, visible-infrared, and UV-visible-infrared photodetectors are preferred in order to meet the ever-increasing multifunctional requirements. The formation of heterojunction between two materials is advantageous in terms of the suppression of photocarrier recombination and can benefit from different materials’ properties, thus resulting in excellent stability, fast response/recovery time, high responsivity, and enhanced external quantum efficiency [ 9 , 10 , 11 , 12 ]. Wide-bandgap metal oxides such as TiO 2 , NiO, WO 3 , Ga 2 O 3 , ZnO, InO, In 2 O 3 , SnO 2 , and their heterostructures with existing semiconductors are also promising for such a wide range of photodetection and sensing application [ 11 , 12 , 13 , 14 , 15 , 16 ].…”