Influence of substrate off-cut angle on the performance of 310 nm light emitting diodes
J. Cryst. Growth, vol. 526, pp. 125241 (2019).
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The influence of the sapphire substrate off-cut angle from c-plane orientation on the surface morphology of AlN/AlGaN layers and the performance of 310 nm light emitting diode structures has been investigated. Increasing the off-cut angle from 0.1° to 10° towards the m-plane leads to a change of the (Al,Ga)N growth mode, threading dislocation density, and emission characteristics of ultraviolet light emitting diodes (LEDs). The growth mode changed from step-flow with bilayer steps to step-bunching and finally to rough 3D growth. The lowest threading dislocation density has been observed for structures deposited on sapphire with an off-cut angle of 0.65°, whereas the emission power is the highest for structures grown on substrates with an off-cut of 0.48°. Electroluminescence measurements display single peaks for structures on substrates with off-cut angles of up to 0.65°. The emission peak full width at half maximum remains nearly constant (∼9.5 nm) for structures with off-cut angels up to 0.21° and increases to 11.7 nm and 21.0 nm for 0.48° and 0.65°, respectively. The emission wavelength is almost unchanged by the use of off-cut angles up to 0.48° (311 nm) and increases to 319 nm for 0.65°. Larger off-cut angles cause multiple emission peaks indicating compositional inhomogeneity of the InAlGaN quantum wells.
a Ferdinand-Braun-Institut, Leibniz-Institut für Höchstfrequenztechnik, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
b UVphotonics NT GmbH, Gustav-Kirchhoff-Straße 4, 12489 Berlin, Germany
c Technische Universität Berlin, Institute of Solid State Physics, Hardenbergstraße 36, 10623 Berlin, Germany
d Humboldt University of Berlin, Institute of Physics, Newtonstraße 15, 12489 Berlin, Germany
Off-cut, Sapphire substrate, Metal organic vapor phase epitaxy, Ultraviolet, Light emitting diode.