Saurabh Kumar Pandey

Influence of in-situ annealing ambient on p-type conduction in dual ion beam sputtered Sb-doped ZnO thin films

Sb-doped ZnO (SZO) films were deposited on c-plane sapphire substrates by dual ion beam sputtering deposition system and subsequently annealed in-situ in vacuum and in various proportions of O2/(O2 + N2)% from 0% (N2) to 100% (O2). Hall measurements established all SZO films were p-type, as was also confirmed by typical diode-like rectifying current-voltage characteristics from p-ZnO/n-ZnO homojunction. SZO films annealed in O2 ambient exhibited higher hole concentration as compared with films annealed in vacuum or N2 ambient. X-ray photoelectron spectroscopic analysis confirmed that Sb5+ states were more preferable in comparison to Sb3+ states for acceptor-like SbZn-2VZn complex formation in SZO films.

p-type conduction from Sb-doped ZnO thin films grown by dual ion beam sputtering in the absence of oxygen ambient

Sb-doped ZnO (SZO) thin films were deposited on c-plane sapphire substrates by dual ion beam sputtering deposition system in the absence of oxygen ambient. The electrical, structural, morphological, and elemental properties of SZO thin films were studied for films grown at different substrate temperatures ranging from 200 °C to 600 °C and then annealed in situ at 800 °C under vacuum (pressure ∼5 × 10−8 mbar). Films grown for temperature range of 200–500 °C showed p-type conduction with hole concentration of 1.374 × 1016 to 5.538 × 1016 cm−3, resistivity of 66.733–12.758 Ω cm, and carrier mobility of 4.964–8.846 cm2 V−1 s−1 at room temperature. However, the film grown at 600 °C showed n-type behavior. Additionally, current-voltage (I–V) characteristic of p-ZnO/n-Si heterojunction showed a diode-like behavior, and that further confirmed the p-type conduction in ZnO by Sb doping. X-ray diffraction measurements showed that all SZO films had (002) preferred crystal orientation. X-ray photoelectron spectroscopy...

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 Cd0.4Zn0.6O/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.

High performance from ZnO multiple quantum-well green light emitting diode with Li-doped CdZnO active region

A comprehensive theoretical study of Cd0.4Zn0.6O/ZnO multiple quantum-well (MQW) based light emitting diode (LED) is performed using a commercial TCAD simulation software. A device internal quantum efficiency (IQE) of ~94% is achieved at room temperature from such LED that, emanates at 510 nm wavelength with a turn-on voltage of 3.1 V. The effects of thickness, doping, and alloy composition of various device constituent layers are comprehensively studied while optimizing the device performance at room temperature. It is also observed that electroluminescence (EL) intensity increased by a factor of 1.25 Li doping (doping concentration=1×1018 cm-3) of CdZnO well region, possibly due to the strain-induced piezoelectric polarization and spontaneous polarization reduction caused by Li ferroelectric dipole moment.

Device modeling and optimization of high- performance thin film CIGS solar cell with Mg x Zn 1−x O buffer layer

A comprehensive device modeling for thin film CIGS-based solar cell with MgZnO buffer layer has been performed. The effects of thickness, doping, and alloy composition of various device constituent layers are extensively studied while optimizing device performance of the solar cell at room temperature. In this study, a maximum power conversion efficiency of 21.4% is achieved with performance parameters of 1.2V for open circuit voltage (Voc), 34.8 mA/cm2 of short circuit current density (Jsc) and a fill factor of 85.7%. Different aspects of constituent layer parameters thickness, doping, and alloy composition calibrations has been considered to identify the optimization criteria for the design of CIGS based solar cell.