A Schottky-Type Metal-Semiconductor-Metal Al0.24Ga0.76N UV Sensor Prepared by Using Selective Annealing

• Published in: Sensors (Basel, Switzerland) Vol. 21; no. 12; p. 4243
• Main Authors: Park, Byeong-Jun, Seol, Jeong-Hoon, Hahm, Sung-Ho
• Format: Journal Article
• Language: English
• Published: Basel MDPI AG 21.06.2021; MDPI
• Subjects: Aluminum; aluminum gallium nitride (AlGaN); Aluminum gallium nitrides; Annealing; Bias; Communication; Current density; Current leakage; Dark current; Electrodes; Gallium nitrides; Gold; Interdiffusion; local breakdown; Organic chemicals; Photoelectrons; Sensors; Spectrum analysis; Transmission electron microscopy; UV-to-visible rejection ratio (UVRR)
• ISSN: 1424-8220; 1424-8220
• DOI: 10.3390/s21124243

Asymmetric metal-semiconductor-metal (MSM) aluminum gallium nitride (AlGaN) UV sensors with 24% Al were fabricated using a selective annealing technique that dramatically reduced the dark current density and improved the ohmic behavior and performance compared to a non-annealed sensor. Its dark current density at a bias of −2.0 V and UV-to-visible rejection ratio (UVRR) at a bias of −7.0 V were 8.5 × 10−10 A/cm2 and 672, respectively, which are significant improvements over a non-annealed sensor with a dark current density of 1.3 × 10−7 A/cm2 and UVRR of 84, respectively. The results of a transmission electron microscopy analysis demonstrate that the annealing process caused interdiffusion between the metal layers; the contact behavior between Ti/Al/Ni/Au and AlGaN changed from rectifying to ohmic behavior. The findings from an X-ray photoelectron spectroscopy analysis revealed that the O 1s binding energy peak intensity associated with Ga oxide, which causes current leakage from the AlGaN surface, decreased from around 846 to 598 counts/s after selective annealing.