Crystal growth and properties of LiAlO_2 and nonpolar GaN on LiAlO_2 substrate

摘要

In this study, the growth and properties of LiAlO_2 material and a nonpolar GaN-based light-emitting-diode (LED) structure on LiAlO_2 have been investigated. The LiAlO_2 material is grown by the Czochralski pulling technique and is used as a substrate for nonpolar nitride growth. An improved surface roughness can be obtained by a four-step polishing process. With subsequent nitridation treatment, a pure M-plane (1010) GaN can be obtained. An electron microscope shows an abundance of cracks that are oriented parallel to the (001) and (100) planes of the LiAlO_2 substrate on the rear surface of GaN. The absence of the polarization-induced electric field of a GaN-based LED structure on LiAlO_2 was shown by using photoluminescence measurements. Therefore, this approach is promising to further increase the luminescence performance of GaN-based LEDs.