Optimization of Al-doped zinc oxide grown on sapphire using dual-plasma-enhanced metal organic chemical vapor deposition for InGaN/GaN light-emitting diodes

Abstract

We prpose Al-doped zinc oxide (AZO) grown on sapphire substrate using dual-plasma-enhanced metal-organic chemical vapor deposition (DPEMOCVD). The crystalline quality, optical properties, and electrical characteristics of AZO depend on the deposition temperature. The AZO thin film grown at 185 oC shows the highest intensity of (002) preferent orientation for X-ray diffraction (XRD) pattern, highest transmittance of 89 %, highest photoluminence (PL) intensity and lowest full-width at half-maximum (FWHM), and highest carrier concentration and mobility of 3.66 ×1021 cm-3 and 10.08 V/cms, which results a very low resistivity of 1.86 ×10-4 Ωcm. The PL peak shows a blue-shift for AZO grown at 185 oC as compared with ZnO bexause of the Burstein-Moss (BM) effect. In addition, the experimental results represent that the optimized Al content for Al-doped ZnO is 2.88 at % under the deposition temperature of 185 oC. Finally, the AZO was deposited on InGaN/GaN light-emitting deodes (LEDs) as transparent conductive layer (TCL). InGaN/GaN LEDs using DPEMOCVD-deposited AZO TCL show a lowest forward resist and highest light output intensity as compared to the those without and with TCL composed of commercial indium-tin-oxide (ITO).