A Substitution for the High-k Dielectric in an AlGaN/GaN Metal-insulator-Semiconductor Heterostructure

Paraelectric state ferroelectric material is proposed as a novel substitution for the conventional high-k dielectric used in AlGaN/GaN metal−insulator-semiconductor (MIS) field-effect transistors. Its superior potential for improving device transconductance is due to its unique switchable polar nature. By self-consistent calculation involving the switchable polarization of the paraelectric, the 2DEG properties and C–V characteristics are investigated and compared for the novel AlGaN/GaN metal−paraelectric-semiconductor (MPS) structure and an equivalent conventional MIS structure. It is shown that owing to the paraelectric polarization, the gate control of the 2DEG density is remarkably enhanced in the MPS structure and the gate capacitance is significantly improved with a smaller threshold voltage. The self-consistent polarization of the paraelectric in the MPS structure is non-linearly dependent on the saturated polarization, which implies an optimum saturated polarization of 5–10 µC/cm² for the paraelectric.