Light Extraction Investigation for Thin-Film GaN Light-Emitting Diodes With Imbedded Electrodes

Light extraction in thin-film GaN light-emitting diodes (LEDs) prepared with Si substrates pretreated by surface roughening and imbedded electrodes were studied. The LEDs were fabricated with a roughened p-GaN layer, followed by epilayer transferring. There are four types of LEDs: conventional LEDs (C-LED), n-side-up thin GaN LEDs with imbedded electrodes and a KOH-roughened n-GaN (first-type LED), p-side-up thin GaN LEDs with a KOH-roughened n-GaN (second-type LED), and n-side-up thin GaN LEDs with imbedded electrodes and without KOH-roughened n-GaN (third-type LED). The electrical properties of the LEDs are almost the same. However, they differ in luminance intensity. The luminance intensities (at 350 mA) of C-LED, first-type, second-type, and third-type LEDs are 3468, 9105, 7610, and 7047 mcd, respectively. The brightest LED is first-type LED. This may be due to emission surface with pyramidal-textured surface and without light shading electrodes. They enhance the light extraction for first-type LEDs.