Enhanced efficiency of GaN-based light-emitting diodes with periodic textured Ga-doped ZnO transparent contact layer

Abstract

GaN-based light-emitting diodes (LEDs) with indium tin oxide (ITO)/Ga-doped ZnO (GZO) composite oxide films serving as a transparent contact layer (TCL) were demonstrated. In this study, the wall-plug efficiency of LEDs (LED-III) with textured ITO/GZO composite TCL can be markedly improved by 200% and 45% of magnitude as compared to conventional LEDs with Ni∕Au TCL(LED-II) and planar ITO/GZO TCL(LED-I), respectively. Compared to LED-II, this enhancement is due to the enhanced light extraction efficiency of ITO/GZO composite TCL with high transparency. Compared to LED-I, ZnO-based TCL with a higher refractive index (n∼2.0) allows further enhancement of light extraction through the creation of a textured structure on transparent conductive oxide TCL deposited on the top surface of LEDs. In addition, the ITO/GZO composite TCL with a thickness of 550nm is far larger than that of Ni∕Au TCL with a thickness of approximately 15nm. Therefore, in addition to the effect of high transparency, the thicker ITO/GZO TCL with low lateral resistance would also act as a current-spreading layer leading to an enhancement of light extraction.

An insight into doping mechanism in Sn–F co-doped transparent conducting ZnO films by correlating structural, electrical and optical properties

“…There is an great importance of transparent conducting oxide (TCO) thin films for different optoelectronic devices such as thin film solar cells [1,2], flat panel liquid crystal displays, light emitting diodes [3,4] etc. The most commonly used TCO in transparent also been attempted to enhance the conductivity of ZnO [35].…”

Mass production and characterization of free-standing ZnO nanotripods by thermal chemical vapor deposition

“…In recent years, studies on synthesis, characterization, and applications of one-dimensional (1D) ZnO nanostructures such as nanowires, nanorods, nanotubes, nanoneedles, nanoscale multipods and nanobelts [1][2][3] have been studied extensively, because ZnO nanostructures have been regarded as a promising nanomaterial in a wide range of applications like solar cells, sensors, light-emitting diodes, piezoelectric nanogenerators, field-effect transistors, and transparent electrodes [4][5][6][7][8][9][10]. Among them, ZnO multipod nanostructures have attracted much attention recently due to many advantages of free-standing ZnO multipod nanostructures in networked or branched nano-scale device applications.…”

Effect of an ITO current spreading layer on the performance of InGaN MQW solar cells

“…The CSL on the top layer, which absence will induce a power loss as a result of increased lateral resistance, however, introduces extra light loss by shading effects. Semitransparent thin Ni/Au layers, used conventionally as ptype CSL in GaN-based optical devices, demonstrate a transmittance of less than 60% in 350-400 nm wavelength regions [10], producing a large amount of light loss. Currently, conductive indium-tin-oxide (ITO) material, which has high transparency in the visible spectral region, serves as CSL for InGaN-based solar cells.…”