Hole transport improvement in CdZnO/ZnO light emitting diodes with wedge shaped electron blocking layers

Carrier transport characteristics of current injected II-VI CdxZn1-xO/ZnO quantum well (QW) light emitting diodes (LEDs) were theoretically studied, by using both conventional square shaped and wedge-shaped electron blocking layers (EBLs). CdZnO/ZnO QW LEDs with wedge EBL layers exhibited a much improved hole injection rate compared to LEDs with square EBL layers. By the enhanced hole injection efficiency, a balance in the injected electron and hole concentrations are promoted. Therefore, the radiative recombination rate is significantly enhanced in the LEDs with wedge-shaped EBL. In addition, we observed that the insertion of the wedge-shaped EBL significantly reduces the efficiency droop which is the reduction of internal quantum efficiency (IQE) with increasing injection current density. It is expected that the CdZnO/ZnO QW LED with a wedge-shaped EBL is advantageous for the high power light emission via the minimization of efficiency droop, especially in the high injection current range.