Abstract:Commercial light emitting diode (LED) materials - blue (i.e., InGaN/GaN multiple quantum wells (MQWs) for display and lighting), green (i.e., InGaN/GaN MQWs for display), and red (i.e., Al0.05Ga0.45In0.5P/Al0.4Ga0.1In0.5P for display) are evaluated in range of temperature (77–800) K for future applications in high density power electronic modules. The spontaneous emission quantum efficiency (QE) of blue, green, and red LED materials with different wavelengths was calculated using photoluminescence (PL) spectro… Show more
“…Figure 6 b illustrates the Al 0.05 Ga 0.45 In 0.5 P/Al 0.4 Ga 0.1 In 0.5 P MQW LED structure for red for display (RD) with a room temperature peak wavelength of 630 nm. The detailed device structure has been discussed earlier 20 – 23 , 26 . The chip sizes are 800 × 1345 µm 2 for BL LED, 191 × 270 µm 2 for BD and GD LEDs, and 300 × 300 µm 2 for RD LED.…”
Section: Methodsmentioning
confidence: 99%
“…The optical and electrical studies were conducted with a varied range of temperatures 77–800 K using a cryostat. The detail of the LEDs and photodiodes measurements and studied are explained previously 20 – 23 , 26 . Figure 7 Images of LEDs.…”
Section: Methodsmentioning
confidence: 99%
“…We first reported a systematic study of the spontaneous emission quantum efficiency (QE) of green LED materials up to 800 K 19 . Then, various commercial LED materials for lighting and display applications have been characterized and evaluated using the temperature-dependent power-dependent photoluminescence (PL) method 20 . Furthermore, developments in the LED quantum well (QW) structures were made for HT applications 21 .…”
The commercial InGaN-based (blue and green) and AlGaInP-based (red) multiple quantum well (MQW) lighting emitting diodes (LEDs) were studied in a wide range of temperatures up to 800 K for their light emission and detection (i.e., LEDs operated under reverse bias as photodiodes (PDs)) characteristics. The results indicate the feasibility of integrating a pair of selected LEDs to fabricate high temperature (HT) optocouplers, which can be utilized as galvanic isolation to replace the bulky isolation transforms in the high-density power modules. A detailed study on LEDs and PDs were performed. The external quantum efficiency (EQE) of the LED and PDs were calculated. Higher relative external quantum efficiency (EQE) and lower efficiency droops with temperatures are obtained from the blue and green LEDs for display compared with the blue one for lighting and red LED for display. The blue for lighting and red for display devices show superior responsivity, specific detectivity (D*), and EQE compared with blue and green for display when operated as PDs. The results suggest that red LED devices for display can be used to optimize HT optocouplers due to the highest wavelength overlapping compared with others.
“…Figure 6 b illustrates the Al 0.05 Ga 0.45 In 0.5 P/Al 0.4 Ga 0.1 In 0.5 P MQW LED structure for red for display (RD) with a room temperature peak wavelength of 630 nm. The detailed device structure has been discussed earlier 20 – 23 , 26 . The chip sizes are 800 × 1345 µm 2 for BL LED, 191 × 270 µm 2 for BD and GD LEDs, and 300 × 300 µm 2 for RD LED.…”
Section: Methodsmentioning
confidence: 99%
“…The optical and electrical studies were conducted with a varied range of temperatures 77–800 K using a cryostat. The detail of the LEDs and photodiodes measurements and studied are explained previously 20 – 23 , 26 . Figure 7 Images of LEDs.…”
Section: Methodsmentioning
confidence: 99%
“…We first reported a systematic study of the spontaneous emission quantum efficiency (QE) of green LED materials up to 800 K 19 . Then, various commercial LED materials for lighting and display applications have been characterized and evaluated using the temperature-dependent power-dependent photoluminescence (PL) method 20 . Furthermore, developments in the LED quantum well (QW) structures were made for HT applications 21 .…”
The commercial InGaN-based (blue and green) and AlGaInP-based (red) multiple quantum well (MQW) lighting emitting diodes (LEDs) were studied in a wide range of temperatures up to 800 K for their light emission and detection (i.e., LEDs operated under reverse bias as photodiodes (PDs)) characteristics. The results indicate the feasibility of integrating a pair of selected LEDs to fabricate high temperature (HT) optocouplers, which can be utilized as galvanic isolation to replace the bulky isolation transforms in the high-density power modules. A detailed study on LEDs and PDs were performed. The external quantum efficiency (EQE) of the LED and PDs were calculated. Higher relative external quantum efficiency (EQE) and lower efficiency droops with temperatures are obtained from the blue and green LEDs for display compared with the blue one for lighting and red LED for display. The blue for lighting and red for display devices show superior responsivity, specific detectivity (D*), and EQE compared with blue and green for display when operated as PDs. The results suggest that red LED devices for display can be used to optimize HT optocouplers due to the highest wavelength overlapping compared with others.
“…The study was extended to other LED materials as well to investigate the QE at high temperatures. Sabbar et al 18 reported InGaN-based and aluminum-gallium-indium-phosphide-based (AlGaInP-based) MQW structures with different peak wavelength (i.e., 450 nm, 470 nm and 630 nm) for high-temperature optoelectronic applications. Moreover, further optimization into InGaN-based structures was proposed to enhance their behaviors at high temperatures, and relatively high QE at high temperatures (i.e., > 200 °C) is observed 19 .…”
This paper reports high-temperature optocouplers for signal galvanic isolation. Low temperature co-fired ceramic (LTCC) technology was used in the design and fabrication of the high-temperature optocoupler package. The optimal coupling behaviors, driving capabilities and response speed of the optocouplers were concentrated and investigated in this paper. Emitters and detectors with different emission and spectral wavelengths were studied to achieve optimal coupling behaviors. Relatively high coupling efficiency is achieved with emitters and detectors of emission and spectral wavelength in the red spectrum (i.e., 620–750 nm), leading to higher current transfer ratios (CTR). To further enhance the electrical performance, optocouplers with multiple detectors in parallel were designed and fabricated. CTR, leakage current and response speed (i.e., propagation delay, rise time and fall time) of the optocouplers were characterized over a range of temperatures from 25 to 250 °C. The CTR degrades at high temperatures, while the leakage current and response speed show little degradation with varying temperatures. Furthermore, the behaviors of the optocouplers with varying temperatures are modeled and analyzed.
“…Wang et al had measured the PL properties in the temperature range of 6-300 K, and found the temperature dependences of the peak energy and linewidth are induced by the localized carrier hopping and thermalization process [8]. PL was used by Sabbar et al to calculate the spontaneous emission quantum efficiency (QE) of blue, green, and red LED from temperature 77 K to 800 K [9]. However, there are few reports about the EL properties of InGaN/GaN LEDs in the low temperature (below 220 K) because T j is hard to determine.…”
Junction temperature (Tj) and current have important effects on light-emitting diode (LED) properties. Therefore, the electroluminescence (EL) spectra of blue and green LEDs were investigated in a Tj range of 120–373 K and in a current range of 80–240 mA based on accurate real-time measurements of Tj using an LED with a built-in sensor unit. Two maxima of the emission peak energy with changing Tj were observed for the green LED, while the blue LED showed one maximum. This was explained by the transition between the donor-bound excitons (DX) and free excitons A (FXA) in the green LED. At low temperatures, the emission peak energy, full width at half maximum (FWHM), and radiation power of the green LED increase rapidly with increasing current, while those of the blue LED increase slightly. This is because when the strong spatial potential fluctuation and low exciton mobility in the green LED is exhibited, with the current increasing, more bonded excitons are found in different potential valleys. With a shallower potential valley and higher exciton mobility, excitons are mostly bound around the potential minima. The higher threshold voltage of the LEDs at low temperatures may be due to the combined effects of the band gap, dynamic resistance, piezoelectric polarization, and electron-blocking layer (EBL).
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