Regensburg 2019 – wissenschaftliches Programm
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DS: Fachverband Dünne Schichten
DS 25: Thin Film Properties: Structure, Morphology and Composition (XRD, TEM, XPS, SIMS, RBS, AFM, ...) Part II
DS 25.1: Vortrag
Freitag, 5. April 2019, 09:30–09:45, H32
Reducing residual stress and dislocation density in AlN films grown on SiC by MOCVD for UV-C LED applications — •Christian J. Zollner1, Abdullah Almogbel1, Burhan Saif Addin1, Michael Iza1, Steven P. DenBaars1,2, James S. Speck1, and Shuji Nakamura1,2 — 1Materials Department, UC Santa Barbara, CA, USA — 2Department of Electrical and Computer Engineering, UC Santa Barbara, CA, USA
In nitride optoelectronics, the most important figures of merit for buffer layers grown on foreign substrates are threading dislocation density (TDD) and residual stress. Residual stress can lead to polarization fields in GaN and AlN, as well as wafer bowing and film cracking. Threading dislocations are detrimental to optical emission efficiencies, laser lifetimes, and carrier mobilities, but growing low TDD nitride buffers has proven more challenging than in conventional semiconductors. I will discuss the tradeoff between low TDD and low stress in MOCVD grown AlN films, and how this tradeoff can be mitigated. As a result, TDD (measured by x-ray diffraction and TEM) has been reduced from 1010 cm−2 to 4× 108 cm−2, and stress (measured with the x-ray radius of curvature method) has been reduced from nearly 2 GPa to below 500 MPa. The mechanisms of TDD and stress reduction are explored using TEM and secondary-ion mass spectroscopy, and theoretical contributions of different sources of stress are calculated and compared with experiment. Significant reductions in both TDD and stress yield higher performance in UV-C LED devices grown on improved AlN/SiC buffers.