Berlin 2012 – scientific programme

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HL: Fachverband Halbleiterphysik

HL 64: GaN: Preparation and Characterization III

HL 64.6: Talk

Wednesday, March 28, 2012, 17:45–18:00, EW 202

STEM and XRD investigations of ultra thin GaInN/GaN quantum wells with high indium content — •Lars Hoffmann¹, Heiko Bremers¹, Holger Jönen¹, Uwe Rossow¹, Thorsten Mehrtens², Marco Schowalter², Andreas Rosenauer², and Andreas Hangleiter¹ — ¹TU Braunschweig, Institute of Applied Physics, Braunschweig, Germany — ²Universität Bremen, Institute of Solid State Physics, Bremen, Germany

While GaN-based blue light emitting devices exhibit exceptionally large internal quantum efficiencies (up to 90% at room temperature) their green counterparts quickly become less efficient at longer wavelength ("green gap"). Using Transmission Electron Microscopy (TEM) and X-ray diffraction (XRD) we have studied ultrathin (< 2nm) quantum well (QW) structures with high indium content suitable for blue-green laser and light emitting diodes. We investigate the homogeneity of indium incorporation into the quantum well and its interface roughness. In order to obtain high indium content quantum wells we need to decrease the growth temperature, leading to poorer optical and structural quality of the GaN barriers. In our XRD and TEM measurements we observe in some cases that indium is also incorporated into the barriers. Depending on growth conditions, we observe an indium tail or even step-like structures in the barriers, caused by excess indium supplied during quantum well growth. Therefore the temperature profile and the gallium/indium ratio during growth need to be optimized to avoid indium segregation and unwanted incorporation into the barriers.