Growth of highly relaxed InGaN pseudo-substrates over full 2-in. wafers

A highly relaxed InGaN buffer layer was demonstrated over a full two-inch c-plane sapphire substrate by metalorganic chemical vapor deposition. The InGaN buffer layer was grown on a 100nm GaN decomposition stop layer with a 3nm thick high indium composition InGaN underlayer. After thermal decomposition of the underlayer at 1000 degrees C, a 200nm thick In0.04Ga0.96N buffer showed 85% biaxial relaxation measured by a high resolution x-ray diffraction reciprocal space map. When used as a pseudo-substrate for the regrowth of InGaN/InGaN multi-quantum wells, the sample showed a 75nm red-shift in room temperature photoluminescence when compared to a co-loaded GaN template reference. The longer emission wavelength is associated with higher indium incorporation in the InGaN layers from the lessening of the compositional pulling effect caused by compressive strain. Using this technique, a simple red light emitting diode was demonstrated with an active layer growth temperature of 825 degrees C and a peak wavelength of 622nm at a current density of 20 Acm(-2). This work represents a unique method to relax a III-nitride based layer over a full substrate. Published under an exclusive license by AIP Publishing.