Fabrication of n-MgZnO/p-Si heterojunction diode: Role of magnesium doping

Abstract

Transparent conducting undoped and magnesium doped zinc oxide (MgZnO) thin films were deposited on glass and p-Si(100) substrates via atmospheric pressure chemical vapor deposition method. Influence of varied Mg content (0, 2, 4 and 6 wt%) on the morphology, structure, optical and electrical behavior of the fabricated n-MgZnO/p-Si heterojunction diodes were evaluated. AFM images of the film containing 6 wt% of Mg revealed dense columns-like morphology and fewer voids on the film's surface. Both the average surface roughness (from 91 ± 5 to 32 ± 2 nm) and the grain size (from 63.5 ± 3.2 to 29.0 ± 1.5 nm) of films were decreased with the increase in Mg content from 0 to 6 wt%. XRD patterns of the studied films showed the polycrystalline hexagonal wurtzite structure of ZnO with preferred lattice orientation along the c-axis at x = 6 wt%. With increasing Mg content, the transmittance of the film was enhanced up to ∼85% accompanied by a blue-shift at the UV absorption edge and the band gap was widened from 3.22 to 3.46 eV. All the n-MgZnO/p-Si heterojunction diodes exhibited clear rectification behavior (a real signature of the p-n junction diode) wherein the electrical parameters were sensitive to the doping concentration. Furthermore, the electrical traits of the diodes were significantly improved due to the inclusion of Mg2+ into the ZnO films. In terms of rectification performance, the diodes prepared at x ≥ 4 wt% were the best. The proposed controlled growth strategy may constitute a basis to realize high-performance nano-optoelectronic heterojunction devices.