Density Functional Theory Study of Polarization-Induced Electron Confinement by Dilute Boron Alloying in ε-Ga₂O₃ Nanometer-Thick Film for High Electron Mobility Transistor

Density functional theory computations were utilized to quantify the polarization discontinuity of 1.8 μC/cm2 in ε-(B0.0625Ga0.9375)2O3/ε-Ga2O3 heterostructure. The polarization effect was sufficient to generate a two-dimensional electron gas (2DEG) at the heterostructure interface without doping. The creation of 2DEG occurred when the BGaO layer thickness exceeded 17 nm, with its density exhibiting a logarithmic increase as the thickness was augmented. However, the trend plateaued when the thickness surpassed 80 nm with a carrier density of 8.17 × 1012 cm–2. Moreover, guided by Griffith's theory and enthalpy calculations, the epitaxial layer could potentially be pseudomorphically grown up to 968 nm under growth conditions of 1000 K with dilute boron alloying. This design heralds the potential for creating a high electron mobility transistor based on ε-BGaO with an epitaxial layer just nanometers thick, well-suited for high-power and radio frequency applications.