Usman Muhammad, Malik Shahzeb, Khan M Ajmal, Hirayama Hideki
Faculty of Engineering Sciences, Ghulam Ishaq Khan Institute of Engineering Sciences and Technology, Topi, 23460, Khyber Pakhtunkhwa, Pakistan.
Nanotechnology. 2021 Mar 3;32(21):215703. doi: 10.1088/1361-6528/abe4f9.
The optoelectronic properties of semiconducting aluminum gallium nitride (AlGaN)-based ultraviolet-B (UVB) light-emitting diodes (LEDs) are crucial for real-world medical applications such as cancer therapy and immunotherapy. However, the performance of AlGaN-based UVB LED devices is still poor due to the low hole injection efficiency. Therefore, we have numerically investigated the performance of AlGaN-based UVB LEDs for the suppression of efficiency droop as well as for the enhancement of hole injection in the multiquantum wells (MQWs). The influence of the undoped (ud)-AlGaN final quantum barrier (FQB), as well as the Mg-doped multiquantum barrier electron blocking layer (p-MQB EBL), on the efficiency droop has been focused on specifically. To evaluate the performance of the proposed device, we have compared its internal quantum efficiency (IQE), carrier concentration, energy band diagram, and radiative recombination rate with the conventional device structure. Furthermore, the influence of Al composition in the Al-graded p-AlGaN hole source layer (HSL) on the operating voltages of the proposed UVB LEDs was considered. The simulation results suggest that our proposed structure has a high peak efficiency and much lower efficiency droop as compared to the reference structure (conventional). Ultimately, the radiative recombination rate in the MQWs of the proposed UVB LED-N structure has increased up to ∼73%, which is attributed to the enhanced level of electron and hole concentrations by ∼64% and 13%, respectively, in the active region. Finally, a high efficiency droop of up to ∼42% in RLED has been successfully suppressed, to ∼7%, by using the optimized ud-AlGaN FQB and the p-MQB EBL, as well as introducing Al-graded p-AlGaN HSL in the proposed UVB LED-N structure.
基于半导体氮化铝镓（AlGaN）的紫外线B（UVB）发光二极管（LED）的光电特性对于癌症治疗和免疫疗法等实际医疗应用至关重要。然而，由于空穴注入效率低，基于AlGaN的UVB LED器件的性能仍然很差。因此，我们对基于AlGaN的UVB LED进行了数值研究，以抑制效率下降并提高多量子阱（MQW）中的空穴注入。特别关注了未掺杂（ud）-AlGaN最终量子势垒（FQB）以及Mg掺杂的多量子势垒电子阻挡层（p-MQB EBL）对效率下降的影响。为了评估所提出器件的性能，我们将其内部量子效率（IQE）、载流子浓度、能带图和辐射复合率与传统器件结构进行了比较。此外，还考虑了Al渐变p-AlGaN空穴源层（HSL）中Al成分对所提出的UVB LED工作电压的影响。模拟结果表明，与参考结构（传统结构）相比，我们提出的结构具有较高的峰值效率和更低的效率下降。最终，所提出的UVB LED-N结构的MQW中的辐射复合率提高了约73%，这归因于有源区中电子和空穴浓度分别提高了约64%和13%。最后，通过使用优化的ud-AlGaN FQB和p-MQB EBL，并在所提出的UVB LED-N结构中引入Al渐变p-AlGaN HSL，RLED中高达约42%的高效率下降已成功抑制至约7%。
