Photoluminescence and photoconductivity in hydrogen-passivated ZnTe

Abstract

Hydrogen passivation effects in undoped p-ZnTe single crystals were studied by photoluminescence (PL) and photoconductivity (PC) measurements. Samples were exposed to r.f. hydrogen plasma at 250 • C for different durations. Before passivation PL peaks were observed at 2.06 eV, 1.47 eV, 1.33 eV and 1.06 eV. After 60 min of exposure, samples showed strong band edge green luminescence at 2.37 eV due to an exciton bound to a Cu acceptor. In PC studies the dark current decreased by a factor of 70 on passivation for 60 min. From the temperature dependence of PC gain, the minority carrier lifetime τ n was found to go through a maximum of 4.5 × 10 −7 s at 220 K before passivation. After 60 min of hydrogenation, τ n remained constant at 4.5 × 10 −7 s for T > 220 K and decreased for T < 220 K. The activation energies of τ n have been determined and show marked changes on passivation for T > 220 K. Comparison between PL and PC studies showed that the deep acceptor level O Te responsible for emission at 2.06 eV is passivated, giving rise to strong band edge emission at 2.37 eV, while emission due to the midgap impurity levels at 1.47, 1.33 and 1.05 eV remained unaffected. The thermal activation energies of PL peaks have also been determined and allow the construction of a defect energy level diagram for ZnTe.

Injection and Optical Spectroscopy of Localized States in II-VI Semiconductor Films

“…The line Еi = 2.34 eV belonging [66] to VZn is not observed in spectra of the radiation recombination in ZnTe films. This fact is also confirming high stoichiometry of the films under study.…”

“…They are due to longitudinal defects and the change of their intensity may point out the change of these defects concentration in the material. Somewhat other energy position of the line due to oxygen (2.06 eV) is reported in [66]. Thus, analysis of the reference data has forced us to conclude that PL lines in the energy interval Е = (1.835÷2.055) eV are rather caused by oxygen, its complexes and phonon repetitions.…”

“…The level Е1 = 0.05 eV is commonly bound with single-charged dislocation Zn V  , and the level Е2 = 0.15 eV is bound with a double-charged 2 Zn V  Zn vacancy [65,66]. In later works the second level is ascribed to Cu as to a traditional residual impurity in ZnTe, and the doublecharged Zn vacancy is supposed to have a more deeper energy level 0.21 eV [66]. It is thought that the energy activation (0.36÷0.40) eV [67,68] is for the common substitution impurity in ZnTe, namely OTe.…”

Annealing time on carrier dynamics of ZnTe nanoparticles embedded in a near ultraviolet-transparent glass

“…Emission electronic transitions from QDs (E QD 1 and E QD 2 ) and the electron-hole recombinations of the bulk-like NCs (E Bulk-like ) can be seen. The PL emission at about 525 nm (2.37 eV) is attributed to deep defects related to zinc vacancies (E V Zn ) [5,23,24] in the ZnTe QDs. The PL emission centered at 630 nm (1.98 eV) is related to oxygen centers (E O ), [5,[25][26][27][28] in both QDs and bulk-like NCs.…”

Photovoltaic effect in polymer-semiconductor heterojunction

“…ZnTe is one of the widest band gap material of II–VI, as a p ‐type compound, which has a direct band gap of 2.26 eV at room temperature15, 16 and 2.39 eV at 10 K 17. This type of semiconductor offers an immense potential for advanced optoelectronic device applications.…”