On the nature of majority and minority traps in β-Ga2O3: A review

In the last decade, researchers and commercial companies have paid great attention to ultrawide bandgap semiconductors especially gallium oxide (Ga2O3). Ga2O3 has very interesting properties such as a bandgap higher than 4.8 eV, high electrical breakdown field and easy to control the doping density. For example, vacancies and impurities play an important role in controlling the n-type conductivity of this material and hence improving the device performance. This review paper discusses mostly the point defects in Ga2O3 and the sources of majority and minority deep levels (traps) in Ga2O3 characterized using different methods such as deep level transient spectroscopy (DLTS), optical DLTS (ODLTS), deep level optical spectroscopy (DLOS) and other techniques. Majority traps such as E1, E2*, E2 and E3 with energies of about 0.56, 0.75, 0.79 and 1.05 eV below the conduction band maximum (CBM), respectively, are the most observed in Ga2O3. These traps are mostly related to impurities such as iron (Fe), silicon (Si), titanium (Ti) and other impurities, or alternatively to gallium or oxygen vacancies. Minorities traps H1, H2 and H3 with energies of about 0.2, 0.3 and 1.3 eV, respectively, above the valence band maximum (VBM) are the most known defects that are related to vacancies. These minorities traps are usually extracted using optical techniques because of the very low hole density in Ga2O3.