Electrical and structural characterization of $AlxGa1−xN/GaN$ heterostructures grown on $LiGaO2$ substrates

In this letter, we report on the properties of a $AlxGa1−xN/GaN$ heterostructure grown on $LiGaO2.$ A two-dimensional electron gas (2DEG) is observed with mobility of 731 cm²/V s at room temperature and 2166 cm²/V s at 77 K. A comparison of the structural quality of the heterostructure as determined by x-ray diffraction shows significant improvement in comparison to a similar structure grown on a sapphire substrate. Secondary ion mass spectroscopy analysis indicates that lithium diffuses into the GaN during growth. The concentration decreases by two orders of magnitude from the substrate to the surface in a 0.8 μm thick GaN film. The enhancement of the mobility of the 2DEG compared to that of electrons in a uniformly doped film is due, in part, to the proximity of the 2DEG to the film surface, where the Li concentration is lower. In addition, we believe that the surface roughness plays a role in the mobility of the 2DEG. Despite these extrinsic factors, the good conductivity of the 2DEG shows the promise of $LiGaO2$ as a substrate for device-quality GaN.