Abstract
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.
Highlights
IntroductionThe peak spontaneous emission QE of InGaN- based LED materials are (79–84)% and (48–60)% at 500 K and 800 K, respectively
We report on the selection of LEDs for HT optocouplers since the LED can function either as a light source in forward biasing mode or as a PD in photovoltaic mode or reverse biased conditions
The work demonstrates the possibility of fabricating HT optocouplers with targeting operating temperature of 500 K
Summary
The peak spontaneous emission QE of InGaN- based LED materials are (79–84)% and (48–60)% at 500 K and 800 K, respectively. The internal quantum efficiency (IQE) is calculated using temperature and intensitydependent electroluminescence (EL) measurements. All three LEDs exhibit more than 70% IQE at 500 K. We report on the selection of LEDs for HT optocouplers (i.e., one is for illumination, and the other is for light detection) since the LED can function either as a light source in forward biasing mode or as a PD in photovoltaic mode (unbiased) or reverse biased conditions. The work aims to fabricate HT optocouplers using different commercial blue, green, and red LEDs for lighting and display applications
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