Reduction of contact resistance on AlGaN/GaN HEMT structures introducing uneven AlGaN layers

A new technique to reduce contact resistance on AlGaN/GaN HEMTs was proposed. This method introduced uneven AlGaN layer structures. 2D device simulations revealed a clear increase in two-dimensional electron gas (2DEG) concentration near the edge regions where the AlGaN layer thickness fluctuated. This fringing effect is useful because metal and high-density 2DEG can approach each other, overcoming an inherent tradeoff involving the AlGaN layer thickness. Experiments demonstrated the effectiveness of this technique, in which contact resistances obtained on some structures with uneven AlGaN layers were lower than the lowest limit for conventional flat AlGaN structures.