We have numerically examined the advantages of thickness- and composition-grading of the electron blocking layer (EBL) in InGaN multiquantum well light-emitting diodes. We have enhanced the hole confinement inside the active region, which is critical in GaN-based devices. Low hole injection is more severe when conventional wide bandgap AlGaN EBL is inserted between the last GaN quantum barrier and the p-GaN layer. The results obtained show reduced valence band offset leading to improved hole injection and enhanced device performance.
In this work, we have analyzed the behavior of optoelectronic characteristics i.e. internal quantum efficiency (IQE) by the influence of piezoelectric field. This effect was not considered in widely reported models such as the Standard ABC model, Rate equation model, and phase-space-filling model. In Gallium Nitride (GaN)-based light-emitting diodes (LEDs), the active region is comprised of InGaN/GaN layers. For the emission of green light, high composition of indium is needed in InGaN layer. As a result, the lattice mismatch between GaN and InGaN layer is highly dominated, which leads to strong piezoelectric field. Our proposed calculation by including piezoelectric field shows better agreement with the experimental IQE of green LED. Meanwhile, we have proposed a single quantum well (SQW) device structure with reduced piezoelectric field as compared to the conventional structure.
We have numerically investigated single quantum well (SQW) green InGaN-based light-emitting diode (LED) by simultaneously grading quantum well (QW), quantum barriers (QBs) and electron blocking layer (EBL). We compared the simulated results and found that our proposed structure has shown significant improvement in the hole injection. In addition, reduction of strong built-in electrostatic field in the proposed structure has improved the light output power by twice, reduced the efficiency droop by ~23% and improved the radiative recombination by ~46% in the proposed structure.
We reduce the problem of asymmetrical distribution of carriers (electrons and holes) by engineering the last barrier and electron blocking layer (EBL) of green indium gallium nitride (InGaN)-based multiquantum well light-emitting diodes. We employ stair-engineered EBL with a graded InGaN last quantum barrier to enhance the device performance. The efficiency droop ratio of the proposed device is ∼15 % at 100 A / cm2. Similarly, the light output power is also enhanced by about three times, as compared to the reference structure. In addition, a carrier transport issue across the active region is also mitigated in our design.
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