Improvements in Light Extraction Efficiency of AlGaInP Light-Emitting Diodes Using Various Chip Processes

• Main Authors: Teng-Hsun Chen, 陳騰勳
• Other Authors: Dong-Sin Wu
• Format: Others
• Language: zh-TW
• Online Access: http://ndltd.ncl.edu.tw/handle/18198286787989412367

碩士 === 國立中興大學 === 精密工程學系所 === 94 === The motivation of this thesis focuses on the enhancement of light extraction efficiency of AlGaInP light-emitting diodes (LEDs) using various chip processes. One approach is to remove the absorbing GaAs substrate, where a etching stop layer, GaInP, should be employed into the LED structure to insure a complete removing process of the GaAs substrate. After the substrate removing process, a gold reflector was deposited on the entire n-GaAs layer as the ohmic contact, and then an electroplating process was proceeded. A thick copper layer was used as a supporting substrate in the present AlGaInP/mirror/Cu LED structure (chip size: 12x12 mil). Under injection currents of 20 and 100 mA, the AlGaInP LEDs with GaAs absorbing substrates showed only 59 and 249 mcd, respectively. An evident improvement in luminous intensity was achieved in the AlGaInP/mirror/Cu LED samples, where 213 and 869 mcd were obtained at 20 and 100 mA, respectively. Another approach in enhancing the light extraction efficiency of AlGaInP LED was accomplished using a surface roughening process. In this process, the Au(170 nm)/AuBe(260 nm)/Au(170 nm) ohmic contact layers were first deposited on the GaP window layer. After the alloy annealing process (480°C for 10 min), the Be atoms will diffuse into the GaP top layer and form non-uniform clusters. The LED samples were then immersed into a mixture 3H3PO4:1H2O2:1H2O solution for 6 min, resulting in a rough GaP surface. The luminous intensity of the AlGaInP LED can increase from 42 to 50 mcd, that is, an 18% enhancement can be achieved via the present non-photolithography surface roughening process. Keywords: LED, AlGaInP, Cu substrate, Reflector, Surface roughening