Crystal growth and properties of LiAlO2 and nonpolar GaN on LiAlO2 substrate

In this study, the growth and properties of LiAlO2 material and a nonpolar GaN-based light-emitting-diode (LED) structure on LiAlO2 have been investigated. The LiAlO2 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 (101̱0) GaN can be obtained. An electron microscope shows an abundance of cracks that are oriented parallel to the (001) and (100) planes of the LiAlO2 substrate on the rear surface of GaN. The absence of the polarization-induced electric field of a GaN-based LED structure on LiAlO2 was shown by using photoluminescence measurements. Therefore, this approach is promising to further increase the luminescence performance of GaN-based LEDs.