Aluminum nitride (AlN) exhibits large breakdown electric fields and high thermal conductivity which allows for excellent miniaturization and power density in high-power electronics.
In this talk, we investigate normally-off vertical n-channel trench MISFETs, with the channel consisting of nominally undoped graded AlGaN. The graded AlGaN layer creates immobile volume charges, and the lack of impurities reduces impurity scattering. The n-doped drift layer is composed of AlN for optimum electric field management. Contacts are placed on AlGaN for low ohmic resistance. Using TCAD simulations, the physics of device operation is studied. For comparison, a conventional impurity-doped FET without PID is taken as reference device. The simulations encompass calculation of local strain, solution of the Poisson-equation and electron and hole continuity equation on a 2-dimensional cross-section of the device. Transfer characteristics, threshold voltage, on-resistance and electric field are discussed. Surface states and interface charges at the nonpolar trench sidewall are included in the study. Finally, technological implementation and experimental results are discussed.
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