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 cm(2)/V s at room temperature and 2166 cm(2)/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 mu m 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. (C) 1999 American Institute of Physics. [S0003-6951(99)04722-1].