Regensburg 2013 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 72: Focus Session: Extended defects in semi- and nonpolar GaN I

HL 72.5: Topical Talk

Thursday, March 14, 2013, 11:30–12:00, H13

Strain and Relaxation in Nonpolar and Semipolar GaN-based LEDs and Laser Diodes — •Kathryn Kelchner, Shuji Nakamura, Steven DenBaars, and James Speck — Materials Department, University of California, Santa Barbara, USA

Due the noncentrosymmetric nature of the hexagonal wurtzite crystal structure, heterostructures employing InN and AlN alloys on the (0001) basal plane of GaN experience large internal electric fields due to discontinuities in spontaneous and piezoelectric polarizations. Alternative crystal orientations that are nonpolar or semipolar in nature may offer improved device performance, however are also subject to anisotropic in-plane strain of lattice mismatched layers which may impact device design due to limits in critical thickness. In this talk, we will overview some of the basic mechanisms of strain relaxation of InGaN and AlGaN layers on nonpolar and semipolar GaN, including dislocation glide along the basal plane, prismatic slip, and crack formation. Measurement techniques for determining onset and degree of strain relaxation in addition to other materials and growth issues for LED and laser diodes on intentionally strain-relaxed buffers will also be covered.