Data for: Carrier transport improvement in ZnO/MgZnO multiple-quantum-well ultraviolet light-emitting diodes by energy band modification on MgZnO barriers
Description
Ultraviolet (UV) light-emitting diodes (LEDs) based on zinc oxide (ZnO) materials have been the subject of many investigations because of their potential applications. ZnO/MgZnO multiple-quantum-well UV LEDs with graded-composition barriers were developed and numerically analyzed in this study. The simulation results demonstrate that an optimized LED with a Mg composition graded from 24% to 2% in each triangular barrier exhibits the highest internal quantum efficiency (IQE) (88.0%) at 200 A/cm2, showing a 31.3% increase from the conventional LED with square barriers. This enhancement is attributed to the modified energy band structures that improve the symmetry in carrier transportation and increase the radiative recombination rate in each ZnO quantum well, thus enhancing the IQE of the device. Also, the different band-offset ratios of the MgZnO/ZnO and InGaN/GaN heterojunction, which lead to the different carrier transport and electroluminescence properties of ZnO- and GaN-based LEDs, were discussed here, which gives researchers new insights into device design for ZnO-based LEDs. Fig. 1. Schematic diagrams of ZnO-based UV LEDs. The distributions of Mg composition in the active region of the conventional LED and the designed LED with graded-composition in each QB from Mg0.24Zn0.76O to MgxZn1−xO (0 ≤ x ≤ 0.24) along the [0001] direction is shown on the right. Fig. 2. IQEs versus forward injection current density of the LEDs with different x values. The inset shows the IQE of LEDs at 200 A/cm2 as a function of x value. Fig. 3. Energy band diagrams of MQWs in the conventional LED (x = 0.24) and the LED with an x value of 0.20 operated under forward bias at 200 A/cm2. Fig. 4. Carrier concentrations near MQWs in the LEDs with x values from 0.24 to 0 at 200 A/cm2. Fig. 5. FWHM of (a) electron and (b) hole concentrations in each QW as a function of Mg composition x. Fig. 6. Distributions of radiative recombination rates in MQWs of LEDs with x values from 0.24 to 0 at 200 A/cm2.