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HL: Halbleiterphysik

HL 27: GaN: Pr
äparation und Charakterisierung

HL 27.11: Vortrag

Mittwoch, 10. März 2004, 17:45–18:00, H15

MOVPE growth of GaN/AlGaN quantum well structures and its impact on the optical properties — •D. Fuhrmann¹, M. Greve¹, N. Riedel¹, U. Rossow¹, G. Ade², P. Hinze², J. Bläsing³, A. Krost³, and A. Hangleiter¹ — ¹TU Braunschweig, Inst. f. Techn. Phys., 38106 Braunschweig; d.fuhrmann@tu-bs.de — ²Physikalisch Technische Bundesanstalt, 38116 Braunschweig — ³Otto-von-Guericke-Univ., Inst. f. Exp. Phys., 39016 Magdeburg

GaN/Al_xGa_1−xN (x≥20%) quantum well (QW) structures were grown by MOVPE on sapphire and SiC substrates in order to realize efficient UV light emitters. It will be shown how growth parameters (substrate, III-V-ratio, Si-doping, pressure) affect the optical properties, determined by photoluminescence (PL) spectroscopy. TEM and XRD measurements reveal smooth surfaces for the upper and lower GaN/Al_xGa_1−xN-interface. AFM pictures of GaN QW-structures on sapphire show microholes, which can be correlated to defects inside the AlGaN buffer layer. In addition, a PL emission around 3.65 eV arising from these defects is observed, whereas for structures on SiC both AFM and PL do not show these features. Varying QW-thickness for QWs on SiC or sapphire yields a nearly linear shift for the PL peak position with different slopes. It is found that for short growth times a nucleation phase takes place for QWs on sapphire which is not seen in the case of SiC substrates. In order to increase the potential barrier, AlN/GaN MQW structures have been grown for comparison. Differences between Al_xGa_1−xN barriers and AlN barriers arising from a different morphology and structural quality as well as different electric fields inside the quantum well will be discussed.