The work function of n-ZnO deduced from heterojunctions with Si prepared by ALD

Abstract

Highly doped n-type ZnO films have been grown on n-type and p-type Si substrates by atomic layer deposition (ALD). Transmission electron microscopy shows columnar growth of the ZnO films with randomly oriented grains and a very thin interfacial layer of SiO x (x ⩽ 2) with a thickness below 0.4 nm to the Si substrate. Current–voltage and capacitance–voltage measurements performed at temperatures from 50 to 300 K reveal a strong rectifying behaviour on both types of substrates with an ideality factor close to unity between 180 and 280 K. Using the classical approach of thermionic emission, the barrier heights of the ZnO/n-Si and ZnO/p-Si junctions have been deduced and consistent values are obtained yielding a work function of n-type ZnO close to 4.65 eV.

Using Atom-Probe Tomography to UnderstandZnO∶Al/SiO2/SiSchottky Diodes

“…3 we compare our estimate ðΦ p − Φ n Þ=2 ¼ −0.084 eV to the expectations for Fermi-level pinning at the charge neutrality level (CNL), for an idealized Schottky junction (electron affinity alignment), and to previously published results on metal/Si and ZnO/Si diodes [5,[32][33][34][35]. With the exception of Ca, AZO/Si, and metal/Si diodes all exhibit Φ n > Φ p , meaning that the Fermi level at the interface is in the lower half of the Si band gap.…”

“…2), but these trends are overwhelmed by the change in band alignment on going from ZnO to AZO as seen by comparing our results to those of Refs. [33][34][35] (Fig. 3).…”

Prediction of high efficiency ZnMgO/Si solar cells suppressing carrier recombination by conduction band engineering

“…The electron affinitiy of Si is 4.05 eV, but for ZnO the values are more uncertain. Jacobi et al 4 reported 3.85–4.5 eV depending on annealing time, while a more recent study by Quemener et al 5 reported ∼4.6 eV. Aranovich et al 6 used a value of 4.35 eV, and this value is also assumed herein.…”

Improved efficiency of n-ZnO/p-Si based photovoltaic cells by band offset engineering

“…were used in this case. By knowing p Si and n Zn(1 À x)MgxO, δ Si and δ Zn(1 À x)MgxO have been evaluated through inverting the carrier concentration versus δ Si and δ Zn(1 À x) MgxO in the formulae for a non-degenerate and degenerate semiconductor, that are respectively: [21,22]. Here, it is also important to point out that the decrease of (0.157 0.06) eV for ΔE C is in agreement with the expected theoretically value of $ 0.1 eV.…”