2018/12/03 by Burhan K. SaifAddin, Abdullah Almogbel, SaifAddin, Burhan K. +17
Engineering · Materials Science · Physics and Astronomy · #Applied Physics (physics.app-ph) #FOS: Physical sciences #Ga2O3 and related materials #GaN-based semiconductor devices and materials #Instrumentation and Detectors (physics.ins-det) #Materials Science (cond-mat.mtrl-sci) #Optics (physics.optics) #Plasma Diagnostics and Applications
paper · pdf · doi:10.48550/arxiv.1812.01125
openalex publication_date 2018/12/03 · openalex created_date 2022/08/01 · openalex updated_date 2026/07/28
The light output of deep ultraviolet (UV-C) AlGaN light-emitting diodes\n(LEDs) is limited due to their poor light extraction efficiency (LEE). To\nimprove the LEE of AlGaN LEDs, we developed a fabrication technology to process\nAlGaN LEDs grown on SiC into thin-film flip-chip LEDs (TFFC LEDs) with high\nLEE. This process transfers the AlGaN LED epi onto a new substrate by\nwafer-to-wafer bonding, and by removing the absorbing SiC substrate with a\nhighly selective SF6 plasma etch that stops at the AlN buffer layer. We\noptimized the inductively coupled plasma (ICP) SF6 etch parameters to develop a\nsubstrate-removal process with high reliability and precise epitaxial control,\nwithout creating micromasking defects or degrading the health of the plasma\netching system. The SiC etch rate by SF6 plasma was ~46 \μ m/hr at a high RF\nbias (400 W), and ~7 \μ m/hr at a low RF bias (49 W) with very high etch\nselectivity between SiC and AlN. The high SF6 etch selectivity between SiC and\nAlN was essential for removing the SiC substrate and exposing a pristine,\nsmooth AlN surface. We demonstrated the epi-transfer process by fabricating\nhigh light extraction TFFC LEDs from AlGaN LEDs grown on SiC. To further\nenhance the light extraction, the exposed N-face AlN was anisotropically etched\nin dilute KOH. The LEE of the AlGaN LED improved by ~3X after KOH roughening at\nroom temperature. This AlGaN TFFC LED process establishes a viable path to high\nexternal quantum efficiency (EQE) and power conversion efficiency (PCE) UV-C\nLEDs.\n