In this Letter, we report on a monolithically integrated β-Ga2O3 NMOS inverter integrated circuit (IC) based on heteroepitaxial enhancement mode (E-mode) β-Ga2O3 metal-oxide-semiconductor field-effect transistors on low-cost sapphire substrates. A gate recess technique was employed to deplete the channel for E-mode operation. The E-mode devices showed an on-off ratio of ∼105 with a threshold voltage of 3 V. In comparison, control devices without the gate recess exhibited a depletion mode (D-mode) with a threshold voltage of [Formula: see text]3.8 V. Furthermore, depletion-load NMOS inverter ICs were fabricated by monolithically integrating D- and E-mode transistors on the same substrate. These NMOS ICs demonstrated inverter logic operation with a voltage gain of 2.5 at VDD = 9 V, comparable with recent GaN and other wide-bandgap semiconductor-based inverters. This work lays the foundation for heteroepitaxial low-cost and scalable β-Ga2O3 ICs for monolithic integration with (ultra)wide bandgap Ga2O3 power devices.
This report demonstrates an ultrawide bandgap β-Ga2O3 flash memory for the first time. The flash memory device realized on heteroepitaxial β-Ga2O3 film had TiN as the floating gate (FG) and Al2O3 as tunneling and gate oxides. A memory window of > 4 V was obtained between the programmed and erased states of the device. The memory states showed negligible degradation in threshold voltage (VTH) even after 5000 s, exhibiting excellent nonvolatility. Furthermore, the device showed a VTH of ~0.3 V after applying a 17 V programming voltage pulse, indicating the potential of electron trapping phenomenon in the FG to achieve enhancement-mode operation in β-Ga2O3 transistors for high-power and logic applications. This study would provide insights for future oxide electronics integrating β-Ga2O3 memory.
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