Schottky barrier height of Ni to β-(AlxGa1-x) 2O3 with different compositions grown by plasma-assisted molecular beam epitaxy

Coherent beta-(AlxGa1-x) O-2(3) films (x = 0, 0.038, 0.084, 0.164) were grown successfully on a Sn-doped beta-Ga2O3 (010) substrate using plasma-assisted molecular beam epitaxy. Atom probe tomography, transmission electron microscopy, and high resolution x-ray diffraction were used to verify the alloy composition and high quality of the films. Schottky diodes were then fabricated using Ni as the Schottky metal. Capacitance- voltage measurements revealed a very low (< 7 x. 10(15) cm(-3)) free charge density in the nominally undoped films. The barrier height and ideality factor were estimated by current-voltage (I-V) measurements performed at temperatures varying from 300 K to 500 K on the Schottky diodes. These measurements revealed that the apparent Schottky barrier height could have similar values for different compositions of beta-(AlxGa1-x) O-2(3). We believe this is attributed to the lateral fluctuation in the alloy's composition. This results in a lateral variation in the barrier height. Therefore, the average Schottky barrier height extracted from I-V measurements could be similar for beta-(AlxGa1-x) O-2(3) films with different compositions.