Paper EM+SS-ThM5
Studies of InGaN Growth Morphology and Its Relationship to Multiple Quantum Well Luminescence

Thursday, October 21, 2010, 9:20 am, Room Dona Ana

It has been suggested that InGaN quantum well (QW) thickness fluctuations, acting in conjunction with piezoelectric fields, are sufficient to cause exciton localization and reduce non-radiative recombination at dislocations [1]. Consequently, the study of InGaN step morphology and the control of InGaN/GaN interfaces may be crucial for understanding and improving blue and green LED quantum efficiency. To this end, a variety of InGaN QW and thin film structures have been grown to determine how the surface roughens when GaN is alloyed with InN. Statistical analysis of the step-height distributions from AFM images shows that the nominally single-layer step heights transition to multiple-layer step heights as InGaN is grown on GaN. Further analysis of the surface-roughness power spectral density suggests that the main smoothing mechanism changes from an evaporation/recondensation mechanism to a surface diffusion mechanism as the growth temperature is lowered to incorporate indium into GaN. Exploiting these two smoothing mechanisms allows the construction of otherwise identical MQW structures with smoother or rougher InGaN QW interfaces. Initial studies of the correlations between QW interface roughness and luminescence intensity suggest that some degree of InGaN QW roughness leads to higher luminescence efficiency, lending credibility to theories that propose a structural-based enhancement of exciton localization. [1] D. M. Graham, et al., J. Appl. Phys. 97 103508 (2005).

This research was supported by the U.S. Department of Energy, Office of Basic Energy Sciences. Sandia National Laboratories is a multi-program laboratory operated by Sandia Corporation, a wholly owned subsidiary of Lockheed Martin Company, for the U.S. Department of Energy’s National Nuclear Security Administration under contract DE-AC04-94AL85000.