Vertical light-emitting diodes with surface gratings and rough surfaces for effective light extraction.
For enhancing the light extraction of a light-emitting diode, surface grating fabrication based on a simple method of combining photoelectrochemical (PEC) etching with phase mask interferometry has been demonstrated. To understand the optimum grating period in forming a surface grating on a vertical light-emitting diode (VLED), we construct a Llyod's interferometer within PEC electrolyte (KOH) to fabricate surface gratings of various periods on VLEDs for comparing their light extraction efficiencies. Also, to compare the effectiveness of light extraction enhancement between surface grating and rough surface, VLEDs with the rough surfaces fabricated with two different KOH wet etching methods are fabricated. The comparisons of VLED characterizations show that among those grating VLEDs, the light extraction is more effective in a VLED of a smaller grating period. Also, compared with VLEDs of rough surfaces, the grating VLEDs of short grating periods (<2 μm) have the higher light extraction efficiencies, even though the root-mean-square roughness of the rough surface is significantly larger than the grating groove depth.
Institute of Photonics and Optoelectronics, National Taiwan University, 1, Roosevelt Road, Section 4, Taipei, 10617 Taiwan.
Chun-Han
CH
Lin
Charng-Gan
CG
Tu
Horng-Shyang
HS
Chen
Chieh
C
Hsieh
Chih-Yen
CY
Chen
Che-Hao
CH
Liao
Yean-Woei
YW
Kiang
C C
CC
Yang
D017076:Computer-Aided Design; D004735:Energy Transfer; D004867:Equipment Design; D019544:Equipment Failure Analysis; D007909:Lenses; D008029:Lighting / Q000295:instrumentation*; D012031:Refractometry / Q000295:instrumentation*; D012666:Semiconductors; D013499:Surface Properties