Photoluminescence of ZnTe and ZnTe:Cr grown by molecular-beam epitaxy

Abstract

Photoluminescence (PL) from undoped and chromium-doped ZnTe epilayers was studied in the spectral range from 0.3 to 2.4 eV over the temperature range from 5 K to room temperature. Films approximately 2 m thick were grown by molecular-beam epitaxy on GaAs substrates. For undoped ZnTe, spectra are dominated by a sharp acceptor-bound-exciton line related to arsenic, with only weak emission observed due to substitutional oxygen ͑O Te ͒. An analysis of strain-induced shifts in excitonic energies was performed to clarify transition assignments for two PL bands near 2.375 and 2.379 eV. For ZnTe:Cr epilayers, the infrared Cr 2+ emission near 2.5 m ͑0.5-0.6 eV͒ was found to be a function of both doping concentration and Zn/ Te beam-equivalent-pressure ratio. Direct excitation of the Cr 2+ ions with 1.89-m light produced emission up to room temperature. Indirect excitation with 514.5-nm light produced emission that could be detected up to 180 K. Luminescence decay curves measured from a ZnTe:Cr film ͓͑Cr͔ϳ1 ϫ 10 18 cm −3 ͒ using pulsed excitation at 355 and at 532 nm indicated two lifetimes: 1 =3 ͑±1͒ s and 2 ജ 10 s. The shorter lifetime agrees with values reported previously for Cr-doped ZnTe bulk crystals and thin films under 1.9-m pulsed excitation.

Structure and Photoluminescence of Pure and Indium-Doped ZnTe Microstructures

“…Compared with the emission of sample A with 1.15% In, this PL shows infrared emission and the emission color cannot be seen by the naked eye, which is consistent with the black color of the sample. Similar to red emission, this infrared emission can be attributed to recombination between indium donor and deep-lying acceptors, such as Y band, which usually appear in wide bandgap semiconductors. , The Y band is related to the lattice imperfection, structure defects, and dislocation, and locates at about 170−270 meV above the valence band. − Here the In(III) may be the dominant acceptor. The optical characteristics of the Y band strongly depend on the impurity density and growth conditions.…”

“…32,33 The Y band is related to the lattice imperfection, structure defects, and dislocation, and locates at about 170-270 meV above the valence band. [34][35][36] Here the In(III) may be the dominant acceptor. The optical characteristics of the Y band strongly depend on the impurity density and growth conditions.…”

EMP Formation in the Co(II) Doped ZnTe Nanowires

“…Actually, it may be confused regarding the EMP peak with LO phonon replica of shallow-trapped exciton emission. Firstly, the largest LO phonon energy is 26 meV in ZnTe materials, [23] which is not in agreement with the energy span between peaks of LFC1 and LFC2 in this nanowire. Thus the emission at the long wavelength side of the band-edge emission band is EMP instead of the LO phonon replica emission.…”

Optical and magnetic properties of transition-metal ions in tetrahedral and octahedral compounds

“…The study of TMIs in tetrahedral compounds is little. In recent years, there has been an increasing interest in the A II B VI and A III B V semiconductor materials doped with transition-metal impurities, for example, ZnTe:Cr [6], ZnS:V [7], ZnSe:V [7][8][9], ZnO:Ni [10], because of their possible important applications [11][12][13][14][15][16]. Most TMIs doped into A II B VI semiconductor materials belong to the tetrahedral structure.…”