First demonstration of hetero-epitaxial ε-Ga2O3 MOSFETs by MOCVD and a F-plasma surface doping

This letter reports on the demonstration of epsilon-phase gallium oxide (epsilon-Ga2O3) based metal-oxidesemiconductor field effect transistors (MOSFETs) for the first time. Phase-pure epsilon-Ga2O3 film was hetero-epitaxially grown on a sapphire substrate by metal organic chemical vapor deposition (MOCVD) using a two-step growth method. The high crystalline quality of the epilayer was confirmed with the X-ray diffraction (XRD), atomic force microscopy (AFM) and scanning electron microscopy (SEM) investigations. Through a proper surface cleaning and CF4-plasma treatment process, fluorine (F) atoms were incorporated and acted as donors in the epsilon-Ga2O3 film, by which the sheet resistance (R-sh) of the epilayer was decreased by 10(5). Based on this F-plasma doped epsilon-Ga2O3 film, MOSFETs with a maximum output current density exceeding 3 mA/mm were successfully demonstrated. The doping profile extracted from the capacitance-voltage (C-V) measurement showed a significant carrier accumulation near the epsilon-Ga2O3 film surface with a peak concentration of 5 x 10(17) cm(-3) and an integrated carrier density of similar to 6.4 x 10(11) cm(-2). The peak electron effective mobility (mu(eff)) within the MOSFET channel was extracted to be as high as 19 cm(2)/Vs, indicating a great potential of epsilon-Ga2O3 based electronics for future high-speed and high-power applications.

Automated summary

This letter reports the demonstration of epsilon-phase gallium oxide (epsilon-Ga2O3) based MOSFETs for the first time. The high crystalline quality of the epilayer was confirmed, and fluorine atoms were incorporated to decrease the sheet resistance. The MOSFETs showed a high output current density and a significant carrier accumulation near the film surface, indicating the potential of epsilon-Ga2O3 based electronics for high-speed and high-power applications.