Comparison of the AlN and GaN crystalline quality on 2-inch silicon substrate via two growth methods

Abstract

Abstract The crystalline quality of aluminum nitride (AlN) and gallium nitride (GaN) has been investigated through two growth methods on 350 μm [1 1 1]-orientation 2-inch silicon substrates. One method employs nitridation with ammonia prior to the growth of a medium temperature AlN layer. The other method is to preflow trimethyl aluminum (TMAl) prior to the growth of a low temperature AlN layer. The growth parameters are the optimized ones under each growth conditions. The thickness of the GaN layer is adjusted to keep the total thickness of the epilayers unchanged. According to the X-ray diffraction (XRD) rocking curves, with preflow TMAl, both the AlN and GaN present fewer dislocation densities. Reciprocal space maps show that with preflow TMAl treatment, the tensile stress is alleviated both in the AlN and GaN layers. With three layers of indium gallium nitride (InGaN) quantum dots separated by GaN barriers added on the as-grown GaN layer, the sample undergone preflow TMAl has more superb photoluminescence performances of both GaN and InGaN than those of the other one. The root-mean-square surface roughness value obtained by atomic force microscopy is larger in the sample with preflow TMAl treatment. It was due to the a little overlong preflow TMAl time. The transmission electron microscopy (TEM) shows the sample undergone preflow TMAl treatment has fewer defects and abrupt interface between AlN and silicon substrate.