Forward current transport mechanism of the vertical β-Ga2O3 diode with a 1.6 nm SiO2 interlayer on Sn-doped (2¯01) substrates

In this work, vertical β-Ga2O3 metal-interlayer-semiconductor (MIS) diodes were fabricated on heavily Sn-doped β-Ga2O3(2¯01) substrates, utilizing a 1.6-nm SiO2 interlayer deposited by plasma-enhanced atomic layer deposition. By introducing this ultrathin dielectric, the severe OFF-state leakage current inherent to conventional Schottky barrier diodes (SBDs) on heavily doped substrates is effectively suppressed, achieving a high current ON-/OFF-state ratio (ION/IOFF) over 1010 while maintaining an ultralow specific on-resistance (RON,sp) of 1.08 mΩ cm2. Notably, the pre-breakdown leakage current is reduced by over 103 due to the high band offset at the SiO2/Ga2O3 interface, improving the breakdown voltage from 32 V in the control SBDs to 39 V. To deeply elucidate the forward carrier transport, a tunneling-limited thermionic-field emission (TLTFE) model is used, and an optimized self-consistent analytical framework is developed to overcome the difference between the ideal material parameters and the actual growth material parameters. By executing this rigorous framework, the dielectric-modulated semiconductor zero-bias barrier height (qφB0) is stably determined within a precise window of 0.80–0.85 eV, and the equivalent tunneling barrier (qφT,Eff.) is intrinsically bounded above 2.91 eV. These robust quantitative results definitively demonstrate the transition of the forward transport mechanism from the TFE dominated process in the control SBDs to the newly proposed TLTFE mechanism in the designed MIS diodes. Concurrently, an explicitly extracted upper limit for the interface state density of 1.28 × 1012 cm−2 eV−1 fundamentally confirms the superior interfacial quality of the architecture. This work comprehensively demonstrates the efficacy of the ultrathin dielectric layer in suppressing reverse leakage, enhancing breakdown capability, and reconstructing the carrier transport mechanism, providing a rigorous physical framework for the interface engineering of β-Ga2O3 devices.