Jan 13 (Thu) @ 10:00am: "Strain-relaxed InGaN buffer layers for long wavelength nitride devices," Philip Chan, PhD Defense

https://ucsb.zoom.us/j/82652953274?pwd=R0J1bU9kNWZUWE5JQzZTWGpzaGk4Zz09

Abstract

Despite the InGaN material system spanning the visible spectrum into the near infrared, long wavelength InGaN emitters remain challenging. The lower efficiencies seen in green and red emitters and the lack of electrically injected near infrared emitters is largely due to the 10% lattice mismatch between InN and GaN. In conventional devices, this large lattice mismatch leads to a highly strained active region grown coherently to the underlying GaN template. Strain-relaxed InGaN buffer layers reduce the strain in the active region by providing larger in-plane lattice constants on which to grow devices. In this work, we demonstrate a strain-relaxed InGaN pseudo-substrate in a single MOCVD growth by thermally decomposing an InGaN underlayer. The pseudo-substrates are characterized to confirm the strain state of the InGaN buffer layer and multi-quantum wells are regrown, showing a large red-shifting of emission in photoluminescence when compared to a reference sample. Red LEDs and micro-LEDs are then demonstrated on buffer layers relaxed with this technique. Finally, improvements in growth conditions of the buffer layer are explored to produce relaxed InGaN buffers with low surface roughness.

Bio

Philip Chan received his B.S. in Electrical and Computer Engineering from Rutgers University in 2015. He is currently a Ph.D. candidate in the Department of Electrical and Computer Engineering at UCSB under Prof. Shuji Nakamura.

Hosted by: Prof. Shuji Nakamura

Submitted by: Philip Chan <pchan@ucsb.edu>