Optimization of the active-Layer structure for the deep-UV AlGaN light-emitting diodes

The dependence of the active-layer structure on the performance of the deep-UV AlGaN light-emitting diodes (LEDs) was theoretically investigated with an APSYS simulation program. Several structure parameters such as well width, well number, barrier height, barrier width, and doping type were employed to study how these parameters change the band structures as well as the carrier distributions. The band offset and bowing parameter used in the theoretical analysis were extracted from the experimental results. Theoretical analysis shows that the nonuniform carrier distributions as well as the low hole concentrations, which caused by polarization-induced tilted band structures, play important roles in improving the performance of the AlGaN LEDs. Compensating this asymmetric band structure and increasing the hole density are the important keys to improve the AlGaN LED performance. Numerical simulation results suggest that the higher output power can be obtained when the active layer consists of only one quantum well with a width of 1-3 nm and two thicker n-doped barriers with a small Al composition