Revista de investigación de óptica y fotónica

Improved performance GaN on GaN based LED with novel step of roughnening on backside (N-face) of GaN substrate

E. A. Alias

Homoepitaxial growth of GaN based LEDs on bulk GaN substrate is the way forward for the ultimate LED technology [1]. At this point, such LEDs still exhibit low light extraction efficiency, which subsequently degrades the overall performance of the LEDs. To overcome this, roughening the backside (N-face) of the GaN substrate after the LED growth; e.g [2] has been widely practised in many experiments. In this work, we go into opposite direction by roughening the N-face of the GaN substrate prior to the LED growth. It was found that the peak of external quantum efficiency (EQE) and optical output power of the LED on pre-roughened GaN substrate is 21.6% at 12 mA/cm2 while the LED on post-roughened GaN substrate is 20.6% at 14 mA/cm2 . The preroughnening removed oxides and carbon impurities on the Ga-face of the substrate. Hence, the LED was grown on a clean surface (Ga-face) of GaN substrate and hence, improving its performance. This is unlikely for the LED grown on the post-roughened substrate. Furthermore, in comparison to the post-roughnening, the pre-roughening does not require the additional step for coating on the pGaN surface of LED component which is used in structure