Acceptors in ZnO

Abstract

Zinc oxide (ZnO) has potential for a range of applications in the area of optoelectronics. The quest for p-type ZnO has focused much attention on acceptors. In this paper, Cu, N, and Li acceptor impurities are discussed. Experimental evidence indicates these point defects have acceptor levels 3.2, 1.4, and 0.8 eV above the valence-band maximum, respectively. The levels are deep because the ZnO valence band is quite low compared to conventional, non-oxide semiconductors. Using MoO 2 contacts, the electrical resistivity of ZnO:Li was measured and showed behavior consistent with bulk hole conduction for temperatures above 400 K. A photoluminescence peak in ZnO nanocrystals is attributed to an acceptor, which may involve a Zn vacancy. High field (W-band) electron paramagnetic resonance measurements on the nanocrystals revealed an axial center with g ? ¼ 2.0015 and g == ¼ 2.0056, along with an isotropic center at g ¼ 2.0035. V C 2015 AIP Publishing LLC. [http://dx.

Acceptor-modulated optical enhancements and band-gap narrowing in ZnO thin films

“…12,42 This trend indicates that with low nitrogen doping the electron has an effective role which corresponds to n-type conductivity. However, the inverse conductivity type is observed with higher order of N-doping which is in relation to previous reports, 19,43 The Fermi level stretched towards valence band maxima in this situation as nitrogen supposed to be the acceptor impurity in ZnO, [44][45][46] therefore, it enhances more hole in valence band instead of electrons in conduction band which leads shift of Fermi level near to the valence band maxima to compensate the Law of Mass Action. 47 The relationship of BursteinMoss shift with optical band gap and the conductivity type of material is found quite interesting …”

Investigation of the Properties of Al-doped ZnO Thin Films with Sputtering Pressure Deposition by RF Magnetron Sputtering

“…Zinc oxide (ZnO) has the potential to be applied in the area of liquid crystal display, plasma display panel, organic electroluminescence, and solar cells, due to its wide band gap (3.4 eV) and large exciton binding energy (60 meV), which lead to efficient exciton UV emission at room temperature [1,2]. The properties of ZnO highly rely on dopants, post-deposition treatments, and deposition parameters.…”

Deep levels and acceptors in Zn(Mg)O: effect of N-doping

“…Therefore, the notion that more levels are present deeper in the bandgap cannot be discarded. This may be the reason why the energy level associated with the N O substitutional, which should be present at ∼ E V + 1.2 eV [86,89,135,136], is not observed. It is also important to note that in DLOS all traps found within the depletion region and below the Fermi level contribute to the photocapacitance, independent to their distance from the depletion region edge.…”

“…Whereas first-principles calculations yield acceptor-like levels on the valence band side (700 meV [153]), electrical measurements put the level close to the conduction band (200 meV [35]). The most recent report by McCluskey et al [89] shows a deeper behavior for the Cu level, at 3.21 eV below the CBM.…”

“…Experimentally, the zinc vacancy has been related to the so-called "green luminescence" observed in PL experiments, with emissions at room temperature around 2.5 eV [85,88,89]. Trunk et al suggested that this level is responsible for their DL4 band at E V + 0.6 eV [138] and can interact with the other native defects, creating additional PL bands.…”