iii-nitride ultraviolet light-emitting diodes: approaches for the enhanced efficiency

III-nitride ultraviolet (UV) light-emitting diodes (LEDs) offer marvelous potential for a wide range of applications, including air/water purification, surface disinfection, biochemical sensing, cancer cell elimination, and many more. III-nitride semiconductor alloys, especially AlGaN and AlInN, have drawn significant attention due to their significant advantages that include environmental-friendly material composition, compact in size, longer lifetime, low power consumption, and tunable optical emission. However, the performance of III-nitride UV LEDs in terms of efficiency and output power is still deficient. The presence of high defects and dislocations due to lattice-mismatched epilayers, polarization induced quantum-confined Stark effect, electron overflow with low hole injection efficiency is found to be some of the primary reasons behind it. In this thesis, we have investigated in a concave quantum barrier structure approach for the enhanced device performance of AlGaN UV LEDs. The proposed concave quantum barriers could suppress the electron leakage by significantly reducing the electron mean free path that improves the electron capturing capability in the active region. The proposed structure exhibits an optical power of 9.16 mW at ~284 nm wavelength, which is increased by ~40.5% compared to conventional AlGaN UV LED operating at 60 mA injection current. Additionally, the light extraction efficiency of AlInN nanowire UV LEDs has been studied. The results show that the TM-polarized light extraction efficiency of such UV LED without any passivation is only ~25.2%, whereas the maximum recorded light extraction efficiency is ~40.6% with the utilization of 40 nm HfO2 passivation layer. This study provides a promising approach for enhancing the light extraction efficiency of nanowire UV LEDs