The Study of Pretreated Sapphire Substrate

Sapphire is known as the most commonly used substrate, and it is widely used as the substrate for the growth of GaN films. In this paper, Sapphire substrate is pretreated by melted KOH solution, in which the triangle patterned etched pits are formed, and the interpretation is theoretically given about the triangle shape. In additional, compared the results which are obtained when the etched temperature and time varied. The dislocation is displayed very clearly and accurately, and adapted to the followed lateral epitaxial overgrowth, when the sapphire substrate is pretreated at 280° C for about 60 minutes. The crystal quality is analyzed by high-resolution double crystal X-ray diffraction (DCXRD). The result indicated that the pretreatment of sapphire substrate has less effect on the crystal quality. So the patterned sapphire can serve as lateral epitaxial substrate to decrease the dislocation density of GaN films. High quality GaN films with low dislocation density have been grown by LP MOCVD on the sapphire substrate which is pretreated by a new and simple method in order to overcome those problems existing in the conventional ELO technique.