Dresden 2020 – scientific programme
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HL: Fachverband Halbleiterphysik
HL 58: Nitrides: Preparation and characterization I
HL 58.1: Talk
Thursday, March 19, 2020, 09:30–09:45, POT 112
MOVPE growth of (11-22) AlGaN/AlN on m-plane sapphire — •Humberto Foronda1,2, Sarina Graupeter1, Valeria Bonito-Oliva2, Mike Pietsch2, Priti Gupta1, Norman Susilo1, Frank Mehnke1, Johannes Enslin1, Tobias Schulz2, Tim Wernicke1, Klaus Irmscher2, Martin Albrecht2, and Michael Kneissl1 — 1Institut für Festkörperphysik, Technische Universität Berlin, Berlin — 2Leibniz-Institut für Kristallzüchtung,Berlin
The efficiency of UVC-LEDs emitting below 240 nm drops with decreasing wavelength on (0001) grown AlxGa1−xN. One reason is a change in the optical polarization of the emitted light leading to a reduced light extraction efficiency (LEE). LEDs on semipolar planes, i.e. (11-22), overcome poor LEE due to a rotation of the wurtzite unit cell while decreasing the polarization fields. (11-22) AlxGa1−xN/AlN by metalorganic vapor phase epitaxy (MOVPE) was investigated for realizing UVC-LEDs on this orientation. When growing AlxGa1−xN on (10-10) sapphire, layers with (11-22) orientation were achieved, but a deterioration of the surface morphology due to misoriented grains was observed. The protrusion and density of these grains was reduced by tailoring growth and nitridation conditions on sapphire such that a grain-free planar (11-22) surface was achieved. A reduced growth rate suppressed grains at the surface as well as increasing the pressure during nitridation. (11-22) Al0.65Ga1−0.65N:Si layers with different silicon concentrations were grown, where a minimum resistivity of 0.024 Ω cm was achieved, comparable to results on (0001). AlGaN multiquantum wells revealed 240 nm photoluminescence emission.