Origin of InGaN light-emitting diode efficiency improvements using chirped AlGaN multi-quantum barriers

We analyze efficiency droop reductions in InGaN/GaN light-emitting diodes caused by a chirped AlGaN/GaN multi-quantum barrier (MQB). Such electron barriers are expected to create an additional forbidden energy range above the natural conduction band edge, which reduces the electron leakage current. Advanced numerical device simulations reveal that energy band bending practically eliminates this MQB effect. Instead, we find that the measured efficiency improvement has its origin in enhanced hole injection, which can be more easily accomplished using a single thin AlGaN layer.