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Recently, the use of bottom-TJ geometry in LEDs, which achieves N-polar-like alignment of polarization fields in conventional metal-polar orientations, has enabled enhancements in LED performance due to improved injection efficiency. Here, we elucidate the root causes behind the enhanced injection efficiency by employing mature laser diode structures with optimized heterojunction GaN/In0.17Ga0.83N/GaN TJs and UID GaN spacers to separate the optical mode from the heavily doped absorbing p-cladding regions. In such laser structures, polarization offsets at the electron blocking layer, spacer, and quantum barrier interfaces play discernable roles in carrier transport. By comparing a top-TJ structure to a bottom-TJ structure, and correlating features in the electroluminescence, capacitance-voltage, and current-voltage characteristics to unique signatures of the N- and Ga-polar polarization heterointerfaces in energy band diagram simulations, we identify that improved hole injection at low currents, and improved electron blocking at high currents, leads to higher injection efficiency and higher output power for the bottom-TJ device throughout 5 orders of current density (0.015–1000 A/cm2). Moreover, even with the addition of a UID GaN spacer, differential resistances are state-of-the-art, below 7 × 10−4Ωcm2. These results highlight the virtues of the bottom-TJ geometry for use in high-efficiency laser diodes.
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This content will become publicly available on May 1, 2026
Thermal droop minimization and simulation of opto-electronic properties in blue InGaN/GaN Ga-polar and N-polar tunnel junction nanowire LEDs
From the past research results, it is evident that high-energy blue emission requires higher applied voltage in a blue nanowire light-emitting diode (LED) due to which difficulties such as self-heating and poor efficiency are developed. While designing a nanowire LED with III-nitride materials, the radiative recombination rate is reduced as the internal field of polarization inside the existing Ga-polar LEDs will tilt the energy band. But with the involvement of N-polar characteristics, the polarization field direction is reversed which eventually brings higher efficiency and lower turn-on voltage across the wavelength range. The subject of this work is to design and simulate an N-polar tunnel junction (TJ) blue nanowire LED to obtain better thermal as well as opto-electronic performances with minimal turn-on voltage. Moreover, TJ-LEDs show linear increases in light output powers (LOP) with varying current densities due to lower Auger recombination rates in their multi-quantum wells (MQWs). Within a temperature range of 30–150 , the proposed device obtains a lower thermal droop of 5.2 % at a current density of 40 A/cm2 which is 2.2 times less than the conventional one.
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- Award ID(s):
- 2419509
- PAR ID:
- 10610779
- Editor(s):
- Cheong, Kuan Y
- Publisher / Repository:
- Elsevier
- Date Published:
- Journal Name:
- Materials Science in Semiconductor Processing
- Volume:
- 190
- Issue:
- C
- ISSN:
- 1369-8001
- Page Range / eLocation ID:
- 109326
- Subject(s) / Keyword(s):
- Nanowire Light-Emitting Diodes III-nitride Tunnel junction Quantum efficiency Thermal droop
- Format(s):
- Medium: X
- Sponsoring Org:
- National Science Foundation
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