On the Impact of the Barrier Design, Carrier Density, and Temperature on High-Field Transport Properties in GaN-Based Heterostructures

The impact of the sheet carrier density, the barrier design, the introduction of AlN interlayer, and the substrate temperature on the saturation velocity in ungated GaN-based heterostructures were measured over multiple process runs. In addition, gate-transit delays were extracted on 150-nm transistors to verify the extracted data on a transistor level. Empirical models were derived for the saturation and effective carrier velocity in dependence on all parameters to allow for a simple estimation of the current density for a wide majority of GaN-based heterostructures. In addition, an empirical model for the temperature dependence (up to 400 K substrate temperature) is provided, allowing for a direct estimation of the intrinsic saturation velocity decrease for substrate temperatures close to the operation condition of high-power amplifiers.