Performance enhancement of deep ultraviolet micro-light emitting diodes by decreasing the series resistance

Abstract Although micro-light emitting diodes (micro-LEDs, μLEDs) can improve the current crowding effect and increase the optical power, the self-heating effect of a single μLED at high current remains an urgent challenge to be solved. This significantly restricts the electroluminescence performance of the μLED. The series resistance of the LED is inversely proportional to the square of the mesa size, meaning that the smaller the mesa size, the greater the series resistance and the more serious the self-heating effect becomes. Currently, most solutions focus on reducing the series resistance by minimizing the contact resistance. However, our investigation revealed that the electron blocking layer (EBL) contributes significantly to the series resistance due to the high resistivity of the AlN composition used in the EBL. This further amplifies the resistance and aggravates the self-heating effect. To reduce the self-heating effect and improve the electroluminescence characteristics of μLED, we propose reducing the AlN composition of the EBL to decrease the series resistance. Our results indicate that the AlN composition of the EBL should be slightly higher than that of the quantum barrier layer. An excessively low AlN composition in the EBL lacks the ability to confine electrons effectively, while an excessively high composition causes severe self-heating effects, thereby compromising the electroluminescence performance of the μLED. Our findings demonstrate that by using an EBL with an AlN composition of 0.6, we achieved a maximum internal quantum efficiency of 0.73, an optical power density of 14.1 W/cm 2 , and an efficiency droop of only 2.8% for a 20 μm μLED with an emission wavelength of 275 nm. These findings provide valuable insights into alleviating severe self-heating effects and enhancing the electroluminescence characteristics of deep ultraviolet micro-LEDs.