Dresden 2014 – wissenschaftliches Programm

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HL: Fachverband Halbleiterphysik

HL 89: Metamorphic structures: Bringing together incompatible materials I (Focus session with DF)

HL 89.6: Topical Talk

Donnerstag, 3. April 2014, 11:30–12:00, POT 251

Development of High Performance Semipolar GaN-based Blue and Green Lasers: Control of Stress Relaxation — •James Speck — UCSB Materials Department, Santa Barbara, CA USA

Nonpolar and semipolar GaN-based emitters have demonstrated low droop for LEDs and high performance for laser diodes. In this talk, we present two approaches to high performance blue and green laser diodes: the first using intentionally relaxed InGaN buffer layers for (11-22) oriented laser diodes and the second using selective area growth for (20-21) laser diodes.

For the relaxed (11-22) lasers we used strain compensated AlGaN/InGaN superlattice electron/hole blocking layers on intentionally relaxed InGaN buffer layers. Using this design, lasing at 447 nm was achieved with a threshold currentdensity of 7.2 kA/cm2, which is remarkably lower than previous results. Furthermore, wedemonstrate a 497 nm aquamarine-emitting semipolar (11-22)laser diode under pulsed operation.

For the coherent (20-21) lasers we used limited area epitaxy to minimize the misfit dislocation (MD) formation by preventing pre-existing TDs from entering a patterned mesa. Significant MD formation was suppressed by at least a factor of four for Al0.1Ga0.9N/GaN superlattices, enabling AlGaN-clad structures similar to those used in c-plane LDs. We then demonstrate AlGaN-clad blue (456 nm) LDs with threshold current density (Jth) of 4.5 kA/cm2 and GaN-clad true green (523 nm) LDs with Jth of 12 kA/cm2.