Enhancement of the optoelectronic characteristics of deep ultraviolet nanowire laser diodes by induction of bulk polarization charge with graded AlN composition in AlxGa1-xN waveguide
“…The simulation environment is set to room temperature. At the same time, we also assume that 40% of the polarization charge in the interface is blocked [ 24 – 29 ]. Fig.…”
A deep-ultraviolet (DUV) laser diode (LD) consisting of specifically designed cladding layers involving superlattice nitride alloy has been proposed. Simulation studies of different cladding layers were carried out using Crosslight software. It was found that the proposed structure effectively suppresses the leakage of the optical field from the active region and the optical confinement coefficient is 1.45 times higher than that of the conventional structure. The proposed structure has a significant increase in laser power with a low threshold current. Moreover, the introduction of novel cladding layer suppresses the electron and hole leakage from the multiple quantum well (MQW) region, which provides an attractive solution for increasing the stimulated recombination rate in the MQW region leading to the improvement in the performance of the DUV LD.
Graphical abstract
“…The simulation environment is set to room temperature. At the same time, we also assume that 40% of the polarization charge in the interface is blocked [ 24 – 29 ]. Fig.…”
A deep-ultraviolet (DUV) laser diode (LD) consisting of specifically designed cladding layers involving superlattice nitride alloy has been proposed. Simulation studies of different cladding layers were carried out using Crosslight software. It was found that the proposed structure effectively suppresses the leakage of the optical field from the active region and the optical confinement coefficient is 1.45 times higher than that of the conventional structure. The proposed structure has a significant increase in laser power with a low threshold current. Moreover, the introduction of novel cladding layer suppresses the electron and hole leakage from the multiple quantum well (MQW) region, which provides an attractive solution for increasing the stimulated recombination rate in the MQW region leading to the improvement in the performance of the DUV LD.
Graphical abstract
“…Band structure parameters are calculated by using the 6×6 k.p model [41]. Other simulation parameters including radiative recombination coefficient, Shockley-Read-hall recombination lifetime, and Auger Recombination Coefficient are set to be 0.5×10 -16 m 3 s −1 , 100 ns, and 1×10 -46 m 6 s −1 respectively [42,43]. The energy band offset ratio for AlGaN/AlGaN MQW is set to be 0.70/0.30.…”
The electron blocking layer (EBL) plays a vital role in blocking the electron overflow from an active region in the AlGaN-based deep-ultraviolet light-emitting diode (DUV-LED). Besides the blocking of electron overflow, EBL reduces hole injection toward the active region. In this work, we proposed a DUV nanowire (NW) LED structure without EBL by replacing it with a compositionally continuous graded hole source layer (HSL). Our proposed graded HSL without EBL provides a better electron blocking effect and enhanced hole injection efficiency. As a result, optical power is improved by 48% and series resistance is reduced by 50% with 4.8 V threshold voltage. Moreover, graded HSL without EBL offer reduced electric field within the active region, which leads to a significant increment in radiative recombination rate and enhancement of spontaneous emission by 34% at 254 nm wavelength, as a result, 52% maximum internal quantum efficiency with 24% efficiency drop is reported.
“…The bowing parameter and band offset ratio of AlGaN MQW are assumed to be 0.94 eV and 0.3/0.7 [33]. Other simulation parameters including radiative recombination coe cient, Shockley-Read-Hall (SRH) recombination lifetime and Augur recombination coe cient are set to be 0.5×10 -16 m 3 /s, 100 ns, and 1.0×10 -46 m 3 /s, respectively [34,35]. The Mg activation energy in p-AlGaN is scaled linearly from 170 meV (GaN) to 670 meV ( AlN) [36].…”
In the past, low-pressure mercury (Hg) -based deep-ultraviolet (DUV) lamps have been widely used for DUV applications. The exposure of pathogen to DUV radiation at 254 nm emission has been proven to be an effective way of their inactivation in unmanned environment. However, the low-pressure mercury (Hg) DUV lamps are toxic in nature and it consumes a lot of power too. Therefore, in this work, smart and clean single tunnel junction (TJ) AlGaN-based DUV light-emitting diode (LED) at 254 nm peak wavelength has been proposed. The simulated conventional DUV LED device has maximum internal quantum efficiency (IQE) of 50 % with an efficiency droop of 18 % under 200 A/cm2. The performance of the conventional LED can be improved by employing a 5 nm-thin single layer AlGaN TJ. The calculated result shows that AlGaN TJ-based LED has a maximum IQE of 62 % with an efficiency droop of 15 % under higher injection current. In addition, the TJ LED emitted power has been improved by 34 % compared to the conventional LED structure. Such efficient AlGaN DUV LED at 254 nm emission wavelength will be an effective replacement of Hg-DUV lamp in the future.
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