Thermal Droop Effects in AlGaN Ultraviolet-C Light-Emitting Diodes
Why this work is in the frame
A frame that forgets how it found something cannot be audited. These are the routes that admitted this work.
Bibliographic record
Abstract
Al-rich AlGaN based light-emitting diodes (LEDs) operating in the ultraviolet-C (UV-C) spectral wavelength (<280 nm) are important for various critical applications. However, to date, the efficiency of UV-C LEDs remains significantly low in these challenging wavelengths. Here, we have demonstrated that, unlike several established reasons, thermal effects (including self-heating and thermal droop) could cause severe efficiency degradation in UV-C LEDs. Infrared thermal imaging was utilized to measure the accurate internal temperature of epitaxially grown and fabricated UV-C LED heterostructure on nanopatterned sapphire substrate (NPSS). The temperature-dependent measurements show reduced light output and efficiency when operating at increasing ambient temperatures up to 85 °C. We have compared UV-C LED chips of different sizes to correlate these findings with the device area. For a 250 × 500 μm 2 device, the peak light output power (LOP) was ∼29.4 mW at 340.5 A/cm 2, while the peak LOP for a 500 × 500 μm 2 device was ∼45 mW at 270.3 A/cm 2 . Though the maximum achievable efficiency was significantly limited by thermal droop, the external quantum efficiency in the smaller device was measured to be 0.8% higher because of improved light extraction efficiency. Thermal imaging-based experiments and heat diffusion equation-based numerical analysis indicate that smaller devices can sustain higher temperatures until they reach thermal droop.
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Full frame distilled prediction
Teacher imitationNot calibrated prevalence, not ground truth. Human validation pending. Learned from the 10,348 direct Codex labels and 10,348 direct Gemma labels. Candidate is the union of thresholded teacher heads; consensus is their intersection. These outputs are machine_predicted_unvalidated and are not human labels or direct frontier model labels.
Codex and Gemma teacher scores by category
| Category | Codex | Gemma |
|---|---|---|
| Metaresearch | 0.001 | 0.000 |
| Meta-epidemiology (narrow) | 0.000 | 0.000 |
| Meta-epidemiology (broad) | 0.001 | 0.000 |
| Bibliometrics | 0.000 | 0.000 |
| Science and technology studies | 0.000 | 0.000 |
| Scholarly communication | 0.000 | 0.000 |
| Open science | 0.000 | 0.000 |
| Research integrity | 0.000 | 0.000 |
| Insufficient payload (model declined to judge) | 0.001 | 0.000 |
Machine scores (provisional)
The two teacher heads of the student model, read on this work. A score orders the frame for review; it never asserts a category, and the validation status ships verbatim with every row.
Baseline scores from an immature model (maturity gate not passed, 7 training rounds). Scores rank; they never assert a category.
score_only:v0-immature-baseline · verbatim from the scoring run: score_only means the number may rank works, and no category label ships from it