GaN‐based Schottky barrier ultraviolet photodetector with a 5‐pair AlGaN–GaN intermediate layer

Won

et al. 2017

Sensors

The UV-to-visible rejection ratio is one of the important figure of merits of GaN-based UV photodetectors. For cost-effectiveness and large-scale fabrication of GaN devices, we tried to grow a GaN epitaxial layer on silicon substrate with complicated buffer layers for a stress-release. It is known that the structure of the buffer layers affects the performance of devices fabricated on the GaN epitaxial layers. In this study, we show that the design of a buffer layer structure can make effect on the UV-to-visible rejection ratio of GaN UV photodetectors. The GaN photodetector fabricated on GaN-on-silicon substrate with a step-graded AlxGa−xN buffer layer has a highly-selective photoresponse at 365-nm wavelength. The UV-to-visible rejection ratio of the GaN UV photodetector with the step-graded AlxGa1−xN buffer layer was an order-of-magnitude higher than that of a photodetector with a conventional GaN/AlN multi buffer layer. The maximum photoresponsivity was as high as 5 × 10−2 A/W. This result implies that the design of buffer layer is important for photoresponse characteristics of GaN UV photodetectors as well as the crystal quality of the GaN epitaxial layers.

Section: Introductionmentioning

confidence: 99%

Selectively Enhanced UV-A Photoresponsivity of a GaN MSM UV Photodetector with a Step-Graded AlxGa1−xN Buffer Layer

Won

et al. 2017

Sensors

“…The photoresponse can reach 1350AW −1 at −5V when the incident power density is 5μW cm −2 . This responsibility is three orders of magnitude larger than traditional GaN photodetectors (<0.2A/W) [25,[35][36][37][38]. Such high responsibility can be attributed to high quantum efficiency of ZnO and the sandwiched graphene/h-BN/ZnO structure.…”

Section: Resultsmentioning

confidence: 96%

Graphene/h-BN/ZnO van der Waals tunneling heterostructure based ultraviolet photodetector

Zhong

et al. 2015

Opt. Express

We report a novel ultraviolet photodetector based on graphene/h-BN/ZnO van der Waals heterostructure. Graphene/ZnO heterostructure shows poor rectification behavior and almost no photoresponse. In comparison, graphene/h-BN/ZnO structure shows improved electrical rectified behavior and surprising high UV photoresponse (1350AW(-1)), which is two or three orders magnitude larger than reported GaN UV photodetector (0.2~20AW(-1)). Such high photoresponse mainly originates from the introduction of ultrathin two-dimensional (2D) insulating h-BN layer, which behaves as the tunneling layer for holes produced in ZnO and the blocking layer for holes in graphene. The graphene/h-BN/ZnO heterostructure should be a novel and representative 2D heterostructure for improving the performance of 2D materials/Semiconductor heterostructure based optoelectronic devices.

“…To fabricate the UV photodetector, GaN is one of proper materials because it has a wide bandgap of 3.4 eV corresponding to the UV wavelength region. In the last two decades, various types of GaN-based UV photodetectors or other material-based UV photodetectors were proposed and reported in literatures [ 4 , 5 , 6 , 7 , 8 , 9 , 10 ]. The metal-semiconductor-metal (MSM)-type UV photodetector is the most appropriate device for a development of an optoelectronic integrated circuit compared to those of other-type photodetectors because of its simple fabrication process, low dark current density, and high process compatibility.…”

Section: Introductionmentioning

confidence: 99%

GaN-Based Ultraviolet Passive Pixel Sensor on Silicon (111) Substrate

Won

et al. 2019

Sensors

The fabrication of a single pixel sensor, which is a fundamental element device for the fabrication of an array-type pixel sensor, requires an integration technique of a photodetector and transistor on a wafer. In conventional GaN-based ultraviolet (UV) imaging devices, a hybrid-type integration process is typically utilized, which involves a backside substrate etching and a wafer-to-wafer bonding process. In this work, we developed a GaN-based UV passive pixel sensor (PPS) by integrating a GaN metal-semiconductor-metal (MSM) UV photodetector and a Schottky-barrier (SB) metal-oxide-semiconductor field-effect transistor (MOSFET) on an epitaxially grown GaN layer on silicon substrate. An MSM-type UV sensor had a low dark current density of 3.3 × 10−7 A/cm2 and a high UV/visible rejection ratio of 103. The GaN SB-MOSFET showed a normally-off operation and exhibited a maximum drain current of 0.5 mA/mm and a maximum transconductance of 30 μS/mm with a threshold voltage of 4.5 V. The UV PPS showed good UV response and a high dark-to-photo contrast ratio of 103 under irradiation of 365-nm UV. This integration technique will provide one possible way for a monolithic integration of the GaN-based optoelectronic devices.