Enhanced electrical conductivity and reduced work function of β-Ga2O3 thin films by hydrogen plasma treatment

As a common impurity, H plays a role in tuning the electrical properties of β-Ga2O3 and has attracted immense interest. Despite years of investigations, the influence of H-doping on electrical properties is not always clear due to the lack of comprehensive characterization on both micro- and macro scale. In this work, we investigate the effects of the H-plasma treatment on the electrical properties of β-Ga2O3 films by combining several techniques, from macroscale Hall and photoluminescence measurements to microscale conductive atomic force microscopy (CAFM) and Kelvin probe force microscopy (KPFM). The incorporation of H in β-Ga2O3 not only introduces shallow donor states such as Hi, but also passivates VGa defects by forming the VGa-4H complex. As a result, both the carrier concentration and mobility of H-doped β-Ga2O3 film are significantly increased, corresponding to an enhancement of conductivity by four orders of magnitude in comparison with the intrinsic one. These results correlate well with the local conductivity and surface potential mappings obtained from CAFM and KPFM. Moreover, we found that the work function of β-Ga2O3 thin films can also be tuned by the H-plasma treatment.