High-Temperature Spontaneous Emission Quantum Efficiency Analysis of Different InGaN MQWs for Future Power Electronics Applications

Abstract

The commercial light-emitting diode (LED) epitaxy materials-blue (i.e., InGaN/gallium nitride (GaN) multiple quantum wells (MQWs)) for lighting and display applications and green (i.e., InGaN/GaN MQWs) for display applications-are evaluated with a varied range of temperatures (10-800 K) for future applications in high-density power electronic modules. Six different InGaN/GaN MQW structures (peak wavelengths λ <sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">p</sub> = 448, 467, and 515 nm) are studied and compared to evaluate whether they can satisfy the light output requirements in the optocouplers at high temperatures. The spontaneous emission quantum efficiency (QE) of these LED epitaxy materials are studied using temperature-dependent and power photoluminescence (PL) spectroscopy. The LED materials, which have no pre-QWs, a higher number of QWs, and GaN buffer layer, show the highest QEs at high temperatures. All six LED materials' exhibit 65% QE at 500 K and stable operation at 800 K were without failure or flickering. At 800 K, the spontaneous emission QEs are between 56% and 60% for blue and green LEDs for displays, respectively. This work evaluates the high-temperature capability of various LED epitaxy materials for future applications in the high-temperature optocouplers as the galvanic isolations in high-density power modules.