Optical Characteristics of ZnTeO Thin Films Synthesized by Pulsed Laser Deposition and Molecular Beam Epitaxy

Abstract

Oxygen incorporation into ZnTe was studied using pulsed laser deposition and molecular beam epitaxy. Oxygen incorporation at the high partial pressures studied for pulsed laser deposition was found to result in increasing visible transparency with oxygen incorporation, and is attributed to the formation of TeO x based on bonding information obtained by x-ray photoelectron spectroscopy measurements. Oxygen incorporation by a plasma source during the growth of ZnTe by molecular beam epitaxy was found to result in an electronic band at 0.5 eV below the ZnTe band edge, possessing strong radiative properties and a resonant-like optical absorption coefficient with a peak a > 5000 cm -1 . The ZnTeO thin films grown by MBE have an epitaxial structure similar to ZnTe, where it is unclear whether the properties are due to the formation of a high-density defect level or the formation of a dilute alloy.

Intermediate band solar energy conversion in ZnTeO

“…The quenching of the bandedge PL may be attributed to fast electron relaxation from the conduction band to the 0 Te states, as described from previous time-resolved optical measurements [7]. Optical absorption as a result of the 0 Te states has similarly been reported [8], and is the …”

Oxygen Incorporation in ZnTeO Alloys via Molecular Beam Epitaxy

“…4,5 Although basic IB principles have been verified, small subbandgap photocurrents and loss of output voltage were found to be quite common and difficult to overcome under this configuration of solar cells. 6 More recently, intermediate-band solar cells (IBSCs) using bulk materials have also been demonstrated, especially those based on highly mismatched alloys (HMAs) [7][8][9] in which a small fraction of the host atoms are replaced by an isoelectronic element of very different electronegativity and/or size. IB formation has been confirmed in both nitrogen-doped III-V and oxygen-doped II-VI HMAs.…”

“…IB formation has been confirmed in both nitrogen-doped III-V and oxygen-doped II-VI HMAs. 2,3,[7][8][9][10][11] Despite the bold predictions of high solar energy conversion efficiency for IB materials, demonstration of improved performance over standard semiconductors has not been achieved yet. The success of IB solar cells will likely rely on not only mastering the technology for materials and device preparation but also fundamental research to identify the desired spectrum of electronic states, carrier generation and recombination rates, and carrier transport behaviors.…”

“…To date, only a few reports on the synthesis and fundamental optical properties of ZnTeO and ZnMnTeO have been published. 7,8,10,11 We previously synthesized epitaxial ZnTeO films via both pulsed laser deposition (PLD) and molecular beam epitaxy (MBE). 8 The PLD process was found to result largely in the formation of TeO x , while oxygen was successfully introduced into the lattice of ZnTe by MBE.…”

“…7,8,10,11 We previously synthesized epitaxial ZnTeO films via both pulsed laser deposition (PLD) and molecular beam epitaxy (MBE). 8 The PLD process was found to result largely in the formation of TeO x , while oxygen was successfully introduced into the lattice of ZnTe by MBE. A solar cell device using MBE ZnTeO showed extended spectral response to subbandgap photons, and also demonstrated a 50% increase in power conversion efficiency compared with an undoped ZnTe reference cell.…”