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

• Published in: Sensors (Basel, Switzerland) Vol. 19; no. 5; p. 1051
• Main Authors: Lee, Chang-Ju, Won, Chul-Ho, Lee, Jung-Hee, Hahm, Sung-Ho, Park, Hongsik
• Format: Journal Article
• Language: English
• Published: Switzerland MDPI 01.03.2019; MDPI AG
• Subjects: gallium nitride (GaN); passive pixel sensor (PPS); photodetector; Schottky-barrier (SB) metal-oxide-semiconductor field-effect transistor (MOSFET); ultraviolet (UV); UV image sensor; ultraviolet (UV); UV image sensor; passive pixel sensor (PPS); gallium nitride (GaN); Schottky-barrier (SB) metal-oxide-semiconductor field-effect transistor (MOSFET); photodetector
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s19051051

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 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.