THE EFFECT OF GAN AND ALN BUFFER LAYERS ON GAN FILM PROPERTIES GROWN ON BOTH C-PLANE AND A-PLANE SAPPHIRE

This paper presents a comparative study of the properties of GaN grown by organometallic vapor phase epitaxy, using both a GaN and AlN buffe r layer, as a function of sapphire orientation (c-plane vs a-plane). R esults are presented for varying the thickness of the buffer layer, va rying the growth temperature of the GaN film, and also varying the amm onia/trimethylgallium mass flow ratio. The electron Hall mobilities of GaN films grown on an AlN buffer layer were, in general, higher compa red to films grown using a GaN buffer layer. In addition, growth on a- plane sapphire resulted in higher quality films (over a wider range of buffer thicknesses) than growth on c-plane sapphire. The room tempera ture electron mobilities were also found to be dependent on, not only the growth temperature, but also the ammonia/trimethylgallium mass flo w ratio.