Effect of Al2O3 Passivation on Electrical Properties of $\beta$ -Ga2O3 Field-Effect Transistor

We report on the effect of Al
₂
O
₃
surface passivation on electrical properties of beta-gallium oxide (β-Ga
₂
O
₃
) nanomembrane field-effect transistor (FET). The fabricated bottom-gate β -Ga
₂
O
₃
(100) FET exhibits enhanced channel conductance and reduced hysteresis after the conformal atomic layer deposited Al
₂
O
₃
passivation investigated by high-resolution transmission electron microscope (HR-TEM) analysis. Moreover, abnormal positive threshold voltage (V
_TH
) shifts under negative bias stress are turned into negative V
_TH
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-Al
₂
O
₃
surface passivation is an effective method to improve electrical properties of the bottom-gate β-Ga
₂
O
₃
FET and its device applications.