Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 47: GaN: Devices II
HL 47.1: Vortrag
Donnerstag, 30. März 2006, 15:15–15:30, BEY 118
MOVPE growth of nitride-based green LEDs — •D. Fuhrmann, T. Litte, C. Netzel, H. Bremers, U. Rossow, and A. Hangleiter — TU Braunschweig, Inst. f. Angewandte Physik, Mendelssohnstr. 2, 38106 Braunschweig, Germany
Despite the high efficiencies achieved for blue Ga1−xInxN based light emitting diodes, a significant drop in efficiency occurs towards longer emission wavelengths. This behavior is commonly explained by the diminished crystalline quality of GaInN and increased piezoelectric field due to the higher In content xIn necessary for longer λpeak. By optimizing the MOVPE growth conditions for the active region of green LEDs, we achieved thin quantum wells (QWs) of good material quality with xIn ≥ 25%. The In content was determined by XRD for thicker GaInN layers (≈ 20nm) assuming that xIn is independent of layer thickness. The optical properties of our single QW samples were analyzed using temperature and excitation power dependent PL. It turns out that the PL linewidth, which is due to compositional fluctuations and fluctuations of the QW width, has a strong correlation with the quantum efficiency (QE). We obtained the highest values in terms of the internal QE for quantum wells showing a small PL linewidth. Hence, we find that a homogeneous In composition and smooth GaInN/GaN interfaces are of central importance for the device performance. We processed the QW structures into simple LEDs and performed ”on wafer” measurements. Again, we find the highest optical output power for the structures grown under optimized growth conditions. The internal QE for QWs emitting around 525nm is only 40% lower compared to QWs emitting at 460nm