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

Abstract

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).