Pulsed laser deposition of ITO/AZO transparent contact layers for GaN LED applications

Abstract

In this study, indium-tin oxide (ITO)/Al-doped zinc oxide (AZO) composite films were fabricated by pulsed laser deposition and used as transparent contact layers (TCLs) in GaN-based blue light emitting diodes (LEDs). The ITO/AZO TCLs were composed of the thin ITO (50 nm) films and AZO films with various thicknesses from 200 to 1000 nm. Conventional LED with ITO (200 nm) TCL prepared by E-beam evaporation was fabricated and characterized for comparison. From the transmittance spectra, the ITO/AZO films exhibited high transparency above 90% at wavelength of 465 nm. The sheet resistance of ITO/AZO TCL decreased as the AZO thickness increased, which could be attributed to the increase in a carrier concentration, leading to a decrease in the forward bias of LED. The LEDs with ITO/AZO composite TCLs showed better light extraction as compared to LED with ITO TCL in compliance with simulation. When an injection current of 20 mA was applied, the output power for LEDs fabricated with ITO/AZO TCLs had 45%, 63%, and 71% enhancement as compared with those fabricated using ITO (200 nm) TCL for the AZO thicknesses of 200, 460, and 1000 nm, respectively.

Femtosecond pulsed laser induced growth of highly transparent indium-tin-oxide thin films: Effect of deposition temperature and oxygen partial pressure

“…Several fabrication techniques have been developed for growth of ITO thin films, such as chemical vapor deposition (CVD) [18], magnetron sputtering [19], thermal evaporation [20], vacuum evaporation [21], electron-beam evaporation [22], spray pyrolysis [23], ion-beam sputtering [24], and pulsed laser deposition (PLD) [25].…”

Surface Fermi level pinning and carrier transport of indium-tin-oxide Ohmic contact to p-type GaN

“…Recently, GaN-based LEDs have been fabricated with a single ITO contact without an interlayer to minimize light absorption and hence to increase the extraction efficiency of LEDs. Notably, excellent LED performances with high luminous flux and low forward voltages were reported [5], indicating that the ITO Ohmic contact could be presently formed on a p-GaN surface without the use of interlayer.…”

“…The performance characteristics of the LEDs such as luminescence efficiency and electrical characteristics have been significantly enhanced by improving device properties by producing a novel epitaxial structure, increasing the device design efficiency, and improving the fabrication process and packaging [1,2]. Among these technical advances, the development of an indium-tin-oxide (ITO) electrode, which acts as a current spreader on top of the LEDs and an electrical contact to p-GaN cladding layer, led to a breakthrough in enhancing the electrical and optical performance of GaN-based LEDs [3][4][5]. This could be due to the excellent optical transparency of ITO exceeding 90%, low sheet resistances, and feasible Ohmic contact to p-GaN.…”

Preparation of Highly Transparent (at 450–800 nm) SnO2 Homojunction by Solution Method and Its Photoresponse

“…In recent years, with the rapid development of optoelectronic technology, transparent optoelectronic devices have been widely used in many fields due to their excellent optoelectronic properties, such as solar cells [1], light emitting diodes [2,3], photodetectors [4,5], and so on. The highly transparent PN junction is the basic component of many transparent optoelectronic devices.…”