(Mg,Mn)-dual doping synergism towards luminescence and electrical properties of ZnO/p-Si heterojunction diodes.

In this study, we investigated the impact of divalent dual dopants on ZnO by examining the structural and spectroscopic properties of (Mg,Mn)-doped ZnO thin films deposited using spray deposition technique. Also, we analysed the current-voltage (I-V) characteristics of (Mg,Mn)-doped ZnO/p-Si heterojunctions for potential light-emitting applications. X-ray diffraction of (Mg,Mn)-doped ZnO on glass substrates reveals a compression along the c-axis and a reduction in crystallite size compared to the Mn-doped ZnO film. Moreover, the band gap of Mn-doped ZnO samples increases from 3.29 eV to 3.35 eV with the addition of the Mg dopant. The optical disorder, as estimated through the Urbach tail, increases from 0.33 eV to 0.5 eV with an incremental increase in the concentration of Mg. XPS studies confirmed the substitution of Mn2+ and Mg2+ into Zn2+ in MnMg:ZnO samples. A dominant color of yellow with wavelength 585 nm was recorded, suitable for yellow emitting devices. In the set of fabricated heterojunctions of MnMg:ZnO/Si, 2 at% Mg doped MnZnO film showed a low knee voltage of ∼1.8 V. It was observed that all the MnMg:ZnO/p-Si heterojunctions showed good rectifying behaviour. Various diode parameters were found using transport models such as TE and Norde, wherein a barrier height of ∼0.6-0.7 eV and an ideality factor in the range of ∼1.5-3 was observed. Retention of good crystallinity, slight band gap tuning, apt barrier height, low sheet resistance, and better emission properties were identified for the prepared MgMn:ZnO thin films that find application in optoelectronic devices.

Spectroscopic investigation of Cux Mg0.2-x Zn0.8 S (x = 0, 0.05, 0.10, 0.15) thin films for deep and dilute blue LED applications.

The effect of copper (Cu) doping on the luminescent properties of the spray deposited Mg0.2 Zn0.8 S thin films were investigated for the first time. The Mg0.2 Zn0.8 S film is an excellent luminescent material with strong blue emissions. In the current investigation, we doped Mg0.2 Zn0.8 S with Cu by taking (Cu + Mg) as 20 at% by keeping other element ratios constant. Among the different samples in the series, Cu0.05 Mg0.15 Zn0.8 S has shown promising results with dark blue emission. Also, these films showed good structural formation with lower or no other impurities, which is evident from the X-ray diffraction (XRD). Scanning electron microscopy (SEM), energy-dispersive X-ray spectroscopy (EDX) and atomic force microscopy (AFM) confirmed the improved material quality of Cu0.05 Mg0.15 Zn0.8 S as compared to the pristine. Raman and X-ray photoelectron spectroscopy (XPS) studies have been carried out for the samples. Various defects induced in the films were investigated by recording the photoluminescence (PL) spectra and Cu:(Mg0.2 Zn0.8 S) films exhibited the capability to produce dilute blue luminescence by absorbing ultraviolet (UV) light. The Cu0.05 Mg0.15 Zn0.8 S film showed promising material property, which is suitable for light-emitting diode (LED) applications.