Design and growth optimization by dual ion beam sputtering of ZnO-based high-efficiency multiple quantum well green light emitting diode

This paper presents an in-depth analysis of Cd_0.4Zn_0.6O/ZnO multiple quantum well light emitting diode (LED) using commercial simulation software and experimentally optimized growth conditions of n-type ZnO on Si (001) substrate by dual ion beam sputtering deposition (DIBSD) system. Theoretical study reveals an internal quantum efficiency -93.5% is achieved at room temperature from the device, emitting at 510 nm with a turn-on voltage of 3 V. The effect of substrate temperature and gas composition on ZnO growth has been investigated. Growth parameters optimization is performed using structural, electrical, and optical characterizations. ZnO grown at 600°C shows a strong ZnO (002) X-ray diffraction (XRD) peak at 34.6°, indicating the realization of high-quality c-axis orientation of ZnO layer. Four probe Hall measurements demonstrate achievements of a maximum carrier mobility of -500 cm²/V.s with a low electrical resistivity of ~10^-3 Ω. cm and a carrier concentration of ~10¹⁸ cn^-3 from the grown ZnO samples at room temperature. Results from atomic force microscope (AFM) measurements depict that RMS roughness of ZnO (10 μm × 10 μm) reduces from 44 Å to 10 Å when the substrate temperature is increased from 100°C to 400°C and then increased to 22 Å as the substrate temperature is increased to 600°C. Photoluminescence (PL) studies conducted at room temperature describe a strong band-edge emission at 380 nm from ZnO samples. Prominent PL shoulder peaks are observed at ~485 nm and 618 nm from ZnO grown at 400°C.