Interfacial Structure and Defects in GaN/AlGaN Heterojunction Epitaxially Grown on LiGa02 Substrate by Molecular Beam Epitaxy

Abstract

The performance of III-Nitride based Light Emitting Diodes (LEDs), LASERs, GaN/AlGaN MODFETs (Modulation-doped Field Effect Transistors) and HEMTs (High Electron Mobility Transistors) have been improved dramatically over the past few years [1,2], despite the relatively poor material quality of GaN, as compared to GaAs, for example. The intrinsic properties of the materials system make it extremely well suited to both optoelectronic and microwave power transistor applications. Typically, GaN is grown on substrates such as GaAs, Al2O3 (sapphire) or SiC with large lattice mismatch. This has usually resulted in an extremely high defect density in the GaN layer. The growth of GaN on lithium gallate LiGaO2 (LGO) affords many advantages compared to all other available substrates. LGO offers the smallest average lattice mismatch of any available substrate for the Ill-nitrides. This facilitates the growth of high quality GaN directly on Lithium Gallate without the need for a defective buffer to decouple the strain associated with the large lattice mismatch of other substrates [3].