Dresden 2006 – wissenschaftliches Programm
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HL: Halbleiterphysik
HL 50: Poster II
HL 50.21: Poster
Donnerstag, 30. März 2006, 16:30–19:00, P3
Electro- and photoluminescence investigations of nitride-based blue and green LEDs — •T. Litte, D. Fuhrmann, C. Netzel, H. Bremers, U. Rossow, and A. Hangleiter — TU Braunschweig, Inst. f. Angew. Phys., Mendelssohnstr.2, 38106 Braunschweig, Germany
In recent years very high values of 70% and 40% for the internal quantum efficiency (IQE) of GaInN/GaN based LEDs emitting in the blue and green spectral region, respectively, have been achieved. But still all devices suffer so far from a decrease of the efficiency with increasing drive current. This effect becomes even more pronounced for larger emission wavelengths λpeak. In order to understand the mechanisms limiting the quantum efficiency we present here a detailed analysis of photoluminesence (PL) and electroluminesence (EL) data for blue and green emitting LEDs. The structures were grown by low pressure MOVPE and further processed into simple LEDs. The active region consisted of single and double Ga1−xInxN quantum wells (QWs) with xIn=0.15...0.26 and dQW=1.5nm...3nm and GaN barriers. We used temperature and excitation power dependent PL to determine the IQE. For both blue and green LEDs we find a good aggrement between PL and EL spectra in terms of the linewidth. We observe a very similar shift of the PL and EL peak position with increasing excitation power. As expected the wavelength shift is more pronounced for green LEDs and becomes larger for QWs with larger dQW and smaller xIn compared to QWs emitting at the same λpeak but have smaller dQW and larger xIn. In addition we find that the drop in efficiency at higher current is smallest for LEDs that show the smallest shift of the peak position (i.e. small dQW, large xIn).