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UID:20260728T154740EDT-7528ki5JAX@132.216.98.100
DTSTAMP:20260728T194740Z
DESCRIPTION:Abstract\n\n \n\nAluminum gallium nitride (AlGaN) ultraviolet (
 UV) laser diodes (LDs) are of great research interest due to their wide ra
 nge of applications and promising future to replace today’s dominant UV la
 sing technologies\, such as gas lasers and solid-state lasers. Nonetheless
 \, the majority studies on AlGaN deep UV lasers are still on optical pumpi
 ng and the development of electrically driven counterparts is relatively s
 low\, mainly rooted in the difficulties in achieving high quality AlGaN ep
 ilayers and insufficient p-type conduction. In addition\, the AlGaN UV las
 er research predominantly relies on the structures grown by metalorganic c
 hemical vapor deposition (MOCVD). In contrast\, the research of AlGaN UV l
 asers by molecular beam epitaxy (MBE) is rare. It is also noted that the r
 ecent progress on electrically injected AlGaN deep UV lasers relies on exp
 ensive AlN substrates.\n\nThis thesis follows the track of MBE-grown AlGaN
  on cost-effective foreign substrates\, such as Si and sapphire\, to addre
 ss the current impediments. This thesis first demonstrates a novel buffer 
 layer technology\, which enables low-cost\, highly reproducible\, high qua
 lity\, and nearly strain-free AlN thin film through exploiting the low Al 
 adatom migration during the coalescence process on a GaN nanowire template
  on Si. This thesis further demonstrates high quality AlGaN epilayers on s
 uch nanowire-assisted AlN templates by MBE. Peak internal quantum efficien
 cy (IQE) of ~50% is derived\, which is significantly improved compared to 
 the previously reported bulk AlGaN epilayers on sapphire.\n\nIn parallel\,
  this thesis also\, for the first time\, reports deep UV lasing from MBE-g
 rown AlGaN on sapphire by optical pumping\, with clear lasing evidence. La
 sing at 298 nm from the AlGaN/AlN double heterostructure (DH) is first obt
 ained\, with a lasing threshold of 950 kW/cm2. This thesis further studies
  the correlation between point defects and lasing threshold\, reduces the 
 lasing threshold to 530 kW/cm2 at 287 nm\, together with an increase in IQ
 E of ~16%. Towards the electrically injected AlGaN UV LDs\, this thesis de
 signs and numerically investigates a unique Al-content engineered superlat
 tice electron blocking layer (AESL-EBL)\, which not only improves charge c
 arrier transport with the assistance of hot hole effects but also minimize
 s optical loss due to doping.\n
DTSTART:20230615T140000Z
DTEND:20230615T160000Z
LOCATION:Room 603\, McConnell Engineering Building\, CA\, QC\, Montreal\, H
 3A 0E9\, 3480 rue University
SUMMARY:PhD defence of Xue (Silvana) Yin – Molecular Beam Epitaxy of AlGaN 
 Epilayers on Foreign Substrates for Semiconductor Deep Ultraviolet Lasers
URL:/ece/channels/event/phd-defence-xue-silvana-yin-mo
 lecular-beam-epitaxy-algan-epilayers-foreign-substrates-semiconductor-3486
 87
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