PROCEEDINGS ARTICLE | February 14, 2008
Proc. SPIE. 6910, Light-Emitting Diodes: Research, Manufacturing, and Applications XII
KEYWORDS: Polishing, Quantum wells, Light emitting diodes, Crystals, Indium, Manufacturing, Gallium nitride, Indium gallium nitride, Semiconducting wafers, Surface finishing
Violet and blue Laser diodes, as well as highly efficient high-power Light Emitting Diodes (including any UV
emitters) can be constructed using low-dislocation-density freestanding GaN substrates, either produced as thick
HVPE layers on foreign substrates, or using direct methods of crystallization as ammonothermal one or high
pressure growth from the nitrogen solution in gallium. This paper shows some of the most most important issues
concerning application of such substrates. The first issue is the choice of the substrate thickness influencing the
accommodation of strain, cracking and bowing of the samples. In this point, a new way of prestressing the
substrate by lateral patterning will be presented. The second issue is the surface preparation either by mechanical
polishing and reactive ion etching, or mechano-chemical polishing, in particular, a distribution of defects
revealed by chemical etching will be discussed. Finally, the problem of substrate misorientation influencing the
further morphology and indium incorporation into InGaN quantum wells will be shown. For higher
misorientation of the substrates, the incorporation of indium decreases , but at the same time, the fluctuations of
indium increase giving blue-shifted, weaker and broader photoluminescence peaks.
