Substrate orientation dependent current transport mechanisms in β-Ga₂O₃/Si based Schottky barrier diodes

Sapphire and gallium oxide have been used as substrates for most of the reported results on β-Ga₂O₃ devices. However, silicon (Si) is an abundant material on the Earth, leading to easier and low-cost availability of this substrate, along with higher thermal conductivity, which makes Si a promising and potential substrate candidate for rapid commercialization. Therefore, in order to strengthen the feasibility of Ga₂O₃ on Si integration technology, we have deposited β-Ga2O3 on (100) and (111) oriented p-Si substrates using a pulsed laser deposition technique. A single-phase (β) and polycrystalline nature of the β-Ga₂O₃ film is observed for both samples using x-ray diffraction. A low root mean square roughness of 3.62 nm has been measured for Ga₂O₃/Si(100), as compared to 5.43 nm of Ga₂O₃/Si(111) using atomic force microscope. Moreover, Ga₂O₃/Si(100) shows a smoother and uniform surface of the Ga₂O₃ film, whereas Ga₂O₃/Si(111) seems to have a rougher surface with pitlike defects. This might be due to the hexagonal projection of Si (111) that is not suitable for obtaining a good tilted cuboid or monoclinic Ga₂O₃ crystal unlike the rectangle projection of Si (100). The electrical parameters of the fabricated Schottky barrier diodes were extracted using current–voltage (I–V) and capacitance–voltage (C–V) characteristics. The polycrystalline Ga₂O₃ film on Si(100) leads to fewer defects emerging from the Ga₂O₃/Si heterointerface due to the close symmetry of Ga₂O₃ and the Si(100) crystal with rectangle projections unlike Ga₂O₃ on Si(111). These fewer defects eventually lead to a better diode performance of Ga₂O₃/Si(100) where we have observed typical thermionic dominating carrier transport, whereas defect-assisted thermionic field emission has been the primary carrier transport mechanism in Ga₂O₃/Si(111). Hence, the Si (100) substrate is demonstrated to be a better and potential platform for Ga₂O₃ devices than Si (111).