Investigation of void formation mechanism beneath thin AlN layers grown on foreign substrates

采用氢化物气相外延法在1065℃下在蓝宝石和SiC衬底上生长了不同取向的AlN薄膜。然后，在NH_3 + H_2气流中对衬底进行热处理，温度升至1450℃。有人发现，氢通过薄AlN层扩散到界面通过位错和与衬底反应，这产生薄AlN层下面的空隙。在1450℃生长的AlN厚层中，当界面处的空洞占50%左右时，在生长后的冷却过程中发生了自分离

Thin AlN layers were grown on sapphire and SiC substrates with various orientations at 1065℃by hydride vapor phase epitaxy. Then, heat-treatment of the substrates was performed in NH_3 added H_2 flow up to 1450℃. It was found that hydrogen diffuses through the thin AlN layer to the interface via dislocations and reacts with the substrate, which yields voids beneath the thin AlN layer. Self-separation of thick AlN layers, subsequently grown at 1450℃after the void formation, occurred during post-growth cooling when segment ratio of voids at interface was about 50%