Publications

Results 51–75 of 117

Search results

Jump to search filters

Semi-polar GaN Materials Technology for High IQE Green LEDs

Koleske, Daniel; Lee, Stephen R.; Crawford, Mary H.; Coltrin, Michael E.

The goal of this NETL funded program was to improve the IQE in green (and longer wavelength) nitride- based LEDs structures by using semi-polar GaN planar orientations for InGaN multiple quantum well (MQW) growth. These semi-polar orientations have the advantage of significantly reducing the piezoelectric fields that distort the QW band structure and decrease electron-hole overlap. In addition, semipolar surfaces potentially provide a more open surface bonding environment for indium incorporation, thus enabling higher indium concentrations in the InGaN MQW. The goal of the proposed work was to select the optimal semi-polar orientation and explore wafer miscuts around this orientation that produced the highest quantum efficiency LEDs. At the end of this program we had hoped to have MQWs active regions at 540 nm with an IQE of 50% and an EQE of 40%, which would be approximately twice the estimated current state-of-the-art.

More Details
TYPE SAND Report YEAR 2013
DOIOSTI

Science-based Solutions to Achieve High-performance Deep-UV Laser Diodes (Final LDRD Report)

Crawford, Mary H.; Allerman, A.A.; Armstrong, Andrew A.; Miller, Mary A.; Smith, Michael L.; Cross, Karen C.; Lee, Stephen R.; Henry, Tania A.; Alessi, Leonard J.

We present the results of a three year LDRD project that has focused on overcoming major materials roadblocks to achieving AlGaN-based deep-UV laser diodes. We describe our growth approach to achieving AlGaN templates with greater than ten times reduction of threading dislocations which resulted in greater than seven times enhancement of AlGaN quantum well photoluminescence and 15 times increase in electroluminescence from LED test structures. We describe the application of deep-level optical spectroscopy to AlGaN epilayers to quantify deep level energies and densities and further correlate defect properties with AlGaN luminescence efficiency. We further review our development of p-type short period superlattice structures as an approach to mitigate the high acceptor activation energies in AlGaN alloys. Finally, we describe our laser diode fabrication process, highlighting the development of highly vertical and smooth etched laser facets, as well as characterization of resulting laser heterostructures.

More Details
TYPE SAND Report YEAR 2011
DOIOSTI
Results 51–75 of 117
Results 51–75 of 117