High-Performance GaN-Based LEDs on Si Substrates: The Utility of Ex Situ Low-Temperature AlN Template With Optimal Thickness

Ex situ low-temperature (LT)-AlN templates are employed to realize GaN-based light-emitting diodes (LEDs) on Si substrates by the combination of pulsed laser deposition and metal organic chemical vapor deposition. The influence of ex situ LT-AlN template thickness on the properties and performance of as-grown LEDs has been carefully studied. The LED wafer grown on 70-nm-thick ex situ LT-AlN template exhibits a crack-free surface, good crystalline quality, and excellent multiple quantum wells (MQWs) structural property. The 500 × 500 μm
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LED chips fabricated with lateral structure show the highest light output power of 70.2 mW at an injection current of 300 mA. Through optimizing the thickness of ex situ LT-AlN template, the light output power is greatly improved by 39%. Theoretical analysis has been taken to study the enhancement mechanism of luminous intensity in this LED. It reveals that the residual stress in as-grown wafers is significant to enhance the luminescence of LEDs. The largest residual tensile stress in the LED presents great potential to enhance the carrier injection and transportation, increase the carrier concentrations, and improve the radiative recombination intensity in MQWs, which is crucial to improve the luminous intensity of LEDs.