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

Abstract

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.