Article ID | Journal | Published Year | Pages | File Type |
---|---|---|---|---|
8151426 | Journal of Crystal Growth | 2014 | 31 Pages |
Abstract
We present an epitaxial overgrowth process for reducing threading dislocations in AlxGa1âxN over the entire compositional range. This process avoids the use of UV-absorbing GaN layers and results in a spatially uniform defect reduction which eliminates the need for precise alignment of devices to low-defect areas of the wafer. Using the described overgrowth process, we demonstrate Al0.3Ga0.7N and Al0.6Ga0.4N epilayers with a dislocation density of 2Ã108 cmâ2 and 5Ã108 cmâ2 respectively, rendering them suitable as templates for deep-UV bottom-emitting LEDs and laser diodes. The process involves patterning of submicron-wide-stripes, less than 1 μm in height, into an AlGaN/AlN/sapphire template and subsequent regrowth of a 5-10 μm thick AlGaN epilayer. The sub-micron width of the mesa allows for bending of threading dislocations that would continue to thread vertically through wider mesas. Utilizing 1.3 mm-thick sapphire substrates (3à thicker than commonly used), epilayer cracking from regrowth is eliminated and wafer bow over a 2-in. diameter substrate is reduced to less than 15 μm. We observed a 7à increase in photoluminescence intensity from GaN-AlGaN multi-quantum well structures emitting at 340 nm and a 15à increase in electroluminescence from laser diode heterostructures when grown on patterned Al0.3Ga0.7N templates.
Related Topics
Physical Sciences and Engineering
Physics and Astronomy
Condensed Matter Physics
Authors
A.A. Allerman, M.H. Crawford, S.R. Lee, B.G. Clark,