A unified model for vertical doped and polarized superjunction GaN devices

A unified model is proposed to characterize the breakdown voltage (BV) and specific ON-resistance (R-on,R-sp) for vertical doped superjunction (d-SJ) and polarized superjunction (p-SJ) GaN power devices. This study is based on the recently published compensated-pillar superjunction (cp-SJ) structure. A two-dimensional model for the electric field is analytically formulated using the Green's function method. Numerical calculations and TCAD simulations demonstrate that, for a given pillar depth, the p-SJ device has a lower BV than the d-SJ device with a wide pillar width. However, when the pillar width is less than 200 nm, both devices demonstrate a maximum BV that is close to the intrinsic structure. The R-on,R-sp unified model for the cp-SJ device, taking into account the junction field-effect transistor (JFET) effect in the drift region, also demonstrates that the p-SJ device has a superior R-on,R-sp over the d-SJ device. Considering the recently published impact ionization coefficients, the BV of the p-SJ device is analytically modeled as a function of the pillar depth. Finally, by applying the Lambert W-function, an exact closed-form relationship between R-on,R-sp and BV is presented.Published under license by AIP Publishing.