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In this work, we use Si/Tl5Al1/TiN for a source/drain ohmic contact to demonstrate an ultra-low contact resistance of 0.11 Ω mm (ρc = 2.62 × 10−7 Ω cm2) on non-recessed i-InAlN/GaN heterostructures. The Ti5Al1 alloy was used to suppress the out-diffusion of Al and extract N from the InAlN layer, which aided the formation of ohmic contact by improving the tunneling efficiency of electrons, as we have reported in the past work. A thin Si inter-layer combined with the Ti5Al1 alloy is proposed to further reduce contact resistance. A heavy n-type InAlN layer was obtained through doping with Si atoms to improve the tunneling transport of electrons. Furthermore, the TiN inclusions penetrated into the GaN channel because the in-diffused Si promoted the decomposition of GaN at a high annealing temperature and the in-diffused Ti reacted with GaN. These TiN inclusions provided direct contact with two-dimensional electron gas, offering an additional path for the injection of electrons into the channel. The tunneling and spike mechanism worked alternately to lower the contact resistance at different annealing temperatures (dividing at 900 °C), implying that the joint effect of tunneling and the spike mechanism was initially promoted in the formation of ohmic contact. The mechanism of this Si/Ti5Al1/TiN ohmic contact was fully understood through microscopic and thermodynamic analyses. These results shed light on the mechanism for the formation of ohmic contact in a gold-free metal stack for GaN-based HEMTs. [ABSTRACT FROM AUTHOR]

The high-k nature of HfO2 makes it a competitive gate oxide for various GaN-based power devices, but the high trap densities at the HfO2/GaN interface have hindered the application. This work was specifically carried out to explore the interface between GaN and ozone-based atomic-layer-deposited HfO2 gate oxide. Furthermore, the GaN surface is preoxidized before gate oxide deposition to prepare an oxygen-rich HfO2/GaN interface. On the preoxidized GaN surface, a sharper HfO2/GaN interface and amorphous HfO2 bulk form during the subsequent deposition, translating to improved electric performance in metal–insulator–semiconductor (MIS) devices. The ozone-based HfO2 shows a high breakdown electric field (∼7 MV/cm) and a high dielectric constant (∼28). Furthermore, the MIS high electron mobility transistors' negligible VTH hysteresis and parallel conductance measurements reflect the ultralow trap densities of the HfO2/GaN interface (<1012 cm−2 eV−1). Therefore, the proposed HfO2 gate oxide scheme offers a promising solution for developing GaN MIS devices. [ABSTRACT FROM AUTHOR]

In this article, a β-Ga2O3 metal-interlayer-semiconductor Schottky barrier diode (MIS-SBD) using Al-reacted aluminum oxide as the interlayer is demonstrated for the first time and compared with conventional metal-semiconductor (MS) Schottky barrier diode (SBD). The aluminum oxide is formed by sputtering a thin Al layer on Ga2O3 substrate and then annealed in O2 at 300 °C. With the insertion of Al-reacted interlayer, the SBD subthreshold swing (SS) is significantly improved to 61 mV/dec with an average current range of > 6 orders. Example of atomic layer deposited (ALD) Al2O3 as the interlayer is also fabricated and characterized. J – V study corrected by Gaussian distribution model shows that all the samples statistically exhibit similar mean barrier heights (BHs). This indicates that the interlayer hardly affects the electrostatic field and band bending as experienced by carrier injections. C – V study provides different BH results in different sample setups. The result proves that Al-reacted interfacial layer helps eliminate interface degradation as compared with ALD Al2O3. Overall, MIS-SBD by Al-reaction method exhibits improved SS, reduced reverse leakage current (I0), low ideality factor, good ON-OFF ratio (> 109), and minimized interface charges as compared with its respective counterparts. The result of this article serves as a promising interface engineering technique for Ga2O3-based SBD designs. [ABSTRACT FROM AUTHOR]