New Insights on the Burstein-Moss Shift and Band Gap Narrowing in Indium-Doped Zinc Oxide Thin Films

Abstract

The Burstein-Moss shift and band gap narrowing of sputtered indium-doped zinc oxide (IZO) thin films are investigated as a function of carrier concentrations. The optical band gap shifts below the carrier concentration of 5.61 × 1019 cm-3 are well-described by the Burstein-Moss model. For carrier concentrations higher than 8.71 × 1019 cm-3 the shift decreases, indicating that band gap narrowing mechanisms are increasingly significant and are competing with the Burstein-Moss effect. The incorporation of In causes the resistivity to decrease three orders of magnitude. As the mean-free path of carriers is less than the crystallite size, the resistivity is probably affected by ionized impurities as well as defect scattering mechanisms, but not grain boundary scattering. The c lattice constant as well as film stress is observed to increase in stages with increasing carrier concentration. The asymmetric XPS Zn 2p3/2 peak in the film with the highest carrier concentration of 7.02 × 1020 cm-3 suggests the presence of stacking defects in the ZnO lattice. The Raman peak at 274 cm-1 is attributed to lattice defects introduced by In dopants.

Influence of RF power on the opto-electrical and structural properties of gallium-doped zinc oxide thin films

“…6b-d, the optical band gap of the films increased from 3.33; 3.32; 3.33 to 3.48; 3.47; 3.48 eV from Tauch plot, T´´ and dT/dλ plots, respectively with increasing the RF power from 100 to 200 W. T´´ is second derivative of the transmission is described as T´´(x) = [T(x + h)−2T+(x−h)]/h 2 [34]. Increasing of the band gap energy or shifting of optical absorption edge to higher energy can be explained by Burstein-Moss effect [35] due to increasing of carrier concentration with RF power. Similar behavior of the optical band gap were observed in Ref [28,33,35].…”

“…Increasing of the band gap energy or shifting of optical absorption edge to higher energy can be explained by Burstein-Moss effect [35] due to increasing of carrier concentration with RF power. Similar behavior of the optical band gap were observed in Ref [28,33,35]. In addition a strong and sharp UV absorption edges were observed from 375 to 381 nm for prepared films.…”

Emerging solar cells energy trade-off: Interface engineering materials impact on stability and efficiency progress

“…It is suggested that surface architecture is the fundamental feature to maximize charge accumulation. Stability aspect photoelectrode potential energy barrier is minimized by doping or any means that improves carrier transport properties . Doping may shift the Fermi energy level towards conduction band edge that reduces ΔE or entropy.…”

“…Stability aspect photoelectrode potential energy barrier is minimized by doping or any means that improves carrier transport properties. 82,115 Doping may shift the Fermi energy level towards conduction band edge that reduces ΔE or entropy. Doping or any ways ΔE reduction shift energy level to improve, V oc or overall performance of ESC.…”

Fabrication of Al-Doped ZnO Film with High Conductivity Induced by Photocatalytic Activity

“…23,24 The increased optical bandgap energy is related to the increase of the carrier concentration by UV irradiation, as explained by the Burstein-Moss effect. 19,[25][26][27] Another reason for the decreased resistivity is the Al-ion doping. The amount of Al in the as-deposited film was evaluated by ICPS, confirming the presence of 1.5 ppm Al in the as-deposited film.…”