Reducing forward voltage and enhancing output performance of InGaN-based blue light-emitting diodes using metal dot-embedded transparent p-type finger

Abstract

We investigated the effect of transparent ITO/Ag/ITO multilayer p-type finger on the light output performance of blue GaN-based light emitting diodes (LEDs). The electrical and optical properties of IAI multilayers were characterised as a function of ITO layer thickness. The IAI (30nm/18nm/30nm) multilayers had a transmittance of 94.6% at 450nm, a sheet resistance of 4.49/sq and a Haacke's FOM of 128.15x10(-3-1). LEDs fabricated with reference (Cr/Ni/Au) contact had a forward-bias voltage of 3.72 at an injection current of 50mA and a series resistance of 19.8. On the one hand, LEDs with ITO/Ag/ITO (30nm/18nm/30nm), 2.5-m metal-dots embedded ITO/Ag/ITO and 8-m metal-dots embedded ITO/Ag/ITO p-fingers, respectively, had forward voltages of 3.74, 3.69, 3.56V at 50mA and series resistances of 18.4, 19.7 and 16.1. LED with the 8-m metal-dots embedded ITO/Ag/ITO p-finger yielded 3.37% higher light output at 100mA than the reference LED. The higher light output is attributed to the combined effect of the better current injection and current spreading due to the metal-dot embedded transparent p-type finger.