Effect of Al2O3 Passivation on Electrical Properties of β-Ga2O3 Field-Effect Transistor

We report on the effect of Al2O3 surface passivation on electrical properties of beta-gallium oxide (beta-Ga2O3) nanomembrane field-effect transistor (FET). The fabricated bottom-gate beta-Ga2O3(100) FET exhibits enhanced channel conductance and reduced hysteresis after the conformal atomic layer deposited Al2O3 passivation investigated by high-resolution transmission electron microscope (HR-TEM) analysis. Moreover, abnormal positive threshold voltage (VTH) shifts under negative bias stress are turned into negative VTH shifts, and off-state breakdown characteristics is improved as well. A modeling work using physics-based TCAD shows reduced surface depletion effect after the surface passivation. The results demonstrate that high-quality ALD-Al2O3 surface passivation is an effective method to improve electrical properties of the bottom-gate beta-Ga2O3 FET and its device applications.