부산대학교 도서관

The light output of deep ultraviolet (UV-C) AlGaN light-emitting diodes(LEDs) is limited due to their poor light extraction efficiency (LEE). Toimprove the LEE of AlGaN LEDs, we developed a fabrication technology to processAlGaN LEDs grown on SiC into thin-film flip-chip LEDs (TFFC LEDs) with highLEE. This process transfers the AlGaN LED epi onto a new substrate bywafer-to-wafer bonding, and by removing the absorbing SiC substrate with ahighly selective SF6 plasma etch that stops at the AlN buffer layer. Weoptimized the inductively coupled plasma (ICP) SF6 etch parameters to develop asubstrate-removal process with high reliability and precise epitaxial control,without creating micromasking defects or degrading the health of the plasmaetching system. The SiC etch rate by SF6 plasma was ~46 \mu m/hr at a high RFbias (400 W), and ~7 \mu m/hr at a low RF bias (49 W) with very high etchselectivity between SiC and AlN. The high SF6 etch selectivity between SiC andAlN was essential for removing the SiC substrate and exposing a pristine,smooth AlN surface. We demonstrated the epi-transfer process by fabricatinghigh light extraction TFFC LEDs from AlGaN LEDs grown on SiC. To furtherenhance the light extraction, the exposed N-face AlN was anisotropically etchedin dilute KOH. The LEE of the AlGaN LED improved by ~3X after KOH roughening atroom temperature. This AlGaN TFFC LED process establishes a viable path to highexternal quantum efficiency (EQE) and power conversion efficiency (PCE) UV-CLEDs.