Investigation and Fabrication of GaN-based Blue Light Emitting Diode with High Light Extraction and Quantum Efficiency

Abstract

This dissertation is about the investigation and fabrication of GaN-based LED with high light extraction and quantum efficiency It can be divided into three parts Fist by inserting the 5-nm-thick p-In0 01Ga0 99N layer to MQWs and p-AlGaN we could enhance the electron carrier confinement in the MQW region and hole injection efficiency It was found that we could enhance the output power by 27% It was also found that we could reduce the 20 mA forward voltage from 3 34 V to 2 99 V and the efficiency droop from 36 7% to 23 8% In the second part we demonstrated the GaN-based blue LED with ZnO:Al and AZO:Y transparent conducting layer (TCL) The AZO film forms good ohmic contact with p-GaN without any inserted contact layer after 500℃ RTA annealing The specific contact resistance of annealed AZO and p-GaN is 2 19 × 10-2 Ω‧cm2 It was found that the 20mA forward voltage and output power for LED with AZO on p-GaN upper contacts was almost same with that for LED with AZO on n+-SPS upper contacts Otherwise by adding some ytterbium into the AZO film (i e AZO:Y) we can enhance thermal stability of GaN-based LEDs after high temperature RTA annealing In the third part we demonstrated the GaN-based LEDs with micro-pillars and nano-pillars around the mesa region It was found that output power enhancement of LED with micro-pillars and nano-pillars were about 11% and 48% respectively Otherwise we also report the fabrication of GaN-based LEDs with mesh ITO p-contact and nano-pillars We successfully formed vertical GaN nano-pillars inside the mesh regions and on the mesa-etched regions It was found that we could reach the more than 80% of 20mA-output power improvements of LEDs by combining the PSS mesh ITO p-contact and nano-pillars

Date of Award	2015 Aug 25
Original language	English
Supervisor	Wei-Chi Lai (Supervisor)