Performance Limit of GaN Superjunction Devices

This paper presents a comprehensive analysis and design guidelines for superjunction (SJ) devices in gallium nitride (GaN). The performance limit of GaN SJ structure in the presence of charge imbalance has also been demonstrated. It is illustrated that the optimum specific on-resistance turns to a quadratic function of breakdown voltage instead of a linear dependence when a charge imbalance appears between the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{n}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$\boldsymbol{p}$</tex> pillars. In spite of having a quadratic dependence, an imbalanced SJ performs better than a conventional structure when the level of charge imbalance is lower than 20%. A series of empirical formulae has also been derived to calculate the optimum design parameters such as pillar doping, width, thickness, and corresponding specific on-resistance as a function of the breakdown voltage of interest.