In this study, GaN/AlN and GaN/GaN layers were grown on Al2O3 substrates by atmospheric pressure MO-HVPE system in which metal organic sources can be used for the growth of AlN and GaN buffer layers. For the AlN and GaN buffer layer growth, trimethylaluminum (TMA), trimethylgallium (TMG) and ammonia (NH3) were used as precursors. After the buffer layer growth, thick GaN layers were grown on the AlN/Al2O3 and GaN/Al2O3 substrates, using metallic Ga on which HCl gas was over flown and NH3 as source materials. Growth temperature of the thick GaN layers was 1050℃. We investigated material properties of the thick GaN layers grown on various buffer layers, namely, GaN and AlN buffer layers grown by the MO-HVPE, GaN template grown by conventional MOCVD and ZnO buffer layer deposited by sputter system, by using of XRD (X-ray diffraction), PL (photoluminescence) and CL (cathodoluminescence) measurements. Through PL and CL measurements, we could confirm that the thick GaN grown on AlN buffer layer has better crystal quality than any other buffer layers used in this experiment.
Also as another study, growth of Mg doped thick GaN layers were performed by using of mixed-source HVPE in which metallic Ga mixed with Mg was used as a group III source material for the growth of GaN:Mg. A luminescence peak which might be from Mg related recombination center could be observed in cathodoluminescence (CL) spectroscopy and Auger electron spectroscopy (AES) measurement. From the above results, we suggest that mixed-source HVPE method could be possibly used in the growth of Mg doped thick GaN growth