Effect of copper impurity on the edge emission of ZnTe crystals

The results are given of studies on the edge emission of undoped and copperdoped ZnTe crystals in the temprature range 4.2–300K. The copper impurity has been found to increase the intensity of the principal edge emission band substantially. Analysis of the structure of this emission band indicated that a temprature below 160K the main role is played by the emission from excitons that are most probably bound in Cu_Zn and Li_Zn centers while at higher temperatures it is played by emission during the transition of free electrons to these centers. An appreciable role is played over the entire range of temperatures by emission from free electrons with an energy of 13 MeV. The luminescence quenching energy below 160 K has a value of 7 MeV (the binding energy of a bound exciton) and at higher temperatures it is 78 MeV.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 8, pp. 68–73, August, 1987.     

Mid-IR Cathodoluminescence of Fe:ZnSe

Optics and Spectroscopy - The dependences of the integral intensity and kinetics of mid-IR cathodoluminescence (CL) of Fe:ZnSe crystals on an iron concentration varying from 0.01 to 14 wt % are...     

Investigating the optical properties of a near-surface layer in silicon implanted by zinc after thermal annealing

Changes in the optical properties of a Si layer broken as a result of implantation by Zn ions are investigated during thermal annealing. The investigations are performed by Raman scattering (RS), ellipsometry, and cathodoluminescence (CL). The implanted samples show a broken area with a thickness of about 60 nm with partial amorphization. Thermal treatment at 400°C results in the partial annealing of a radiation point defect while reducing the thickness of the broken layer to 40 nm. The broken layer was completely restored after high-temperature annealing at 700°C.     

Bound-exciton emission bands in ZnSe single crystals and mixed plasmon-phonon modes

The paper reports a cathodoluminescence study of ZnSe single crystals annealed in a Bi melt at 1200 K for 120 h. It is found that the distance between the phonon structure satellites in the bound-exciton series I ₁ ^s -nLO and I ₁ ^d -nLO and the relative satellite intensity are different in samples with different conduction electron concentrations. It is shown that this difference is due to the mixing of the plasmon and phonon modes. The shape of the bound-exciton emission spectrum in ZnSe crystals in the 450–470 nm region is calculated, and a satisfactory agreement with the experiment calculations is obtained.     

Cathodoluminescence of ZnSe(Bi):Al crystals

The cathodoluminescence (CL) in ZnSe crystals annealed at T=1200 K in a Bi melt containing an aluminum impurity is investigated. The spectra are recorded for different excitation levels, temperatures, and detection delay times t ₀. As t ₀ is increased, the intensity of the orange band at λ _max=630 nm (1.968 eV) in the CL spectrum decreases in comparison to the intensity of the dominant yellow-green band at λ _max=550 nm (2.254 eV), whose half-width increases in the temperature range 6–120 K and then decreases as the temperature increases further. It is shown that such behavior of the yellow-green band is caused by the competition between two processes: recombination of donor-acceptor pairs and of free electrons with holes trapped on acceptors. The former mechanism is dominant at low temperatures, and the latter mechanism is dominant at high temperatures. At T∼120 mK the contributions of the two mechanisms to the luminescence are comparable. The resultant structureless band then achieves its greatest half-width, which is dictated by the interaction of the recombining charge carriers with longitudinal-optical and longitudinal-acoustic phonons and with the free-electron plasma. The mean number of longitudinal-optical phonons emitted per photon is determined mainly by their interaction with holes trapped on deep acceptors in the form of Al atoms replacing Se. The donor in the pair under consideration is an interstitial Al atom. Fiz. Tverd. Tela (St. Petersburg) 39, 1526–1531 (September 1997)     

Thermal stability of zincite single crystals

The effect of temperature on the stability of synthetic ZnO crystals in neutral (N₂), oxidative (O₂), and reductive (95% Ar-5% H₂) media and in a low vacuum has been studied. In the first and second cases, zincite does not undergo changes up to 1000°C. After an 8-h exposure in oxygen at 1100°C, a decrease in the size of hexagonal growth hillocks on the monohedron face (0001) and smoothing of its relief on the whole have been observed. In the presence of hydrogen, etching traces manifest themselves on the crystal surface even at 760°C; further heating leads to their sublimation. The effect of annealing on the luminescence properties of zincite has been demonstrated.     

Interaction of excitons in indirect solid solutions of In1−xGaxP at high levels of excitation

The cathode luminescence spectra of GaP and solid solutions of In_1–xGa_xP (with an indirect energy band structure) obtained by liquid-phase epitaxy are investigated at T=77 and 9°K. It is established that the recombination of excitons on neutral donors and the pure exciton recombination with the participation of TA (=13±1 meV), LA (=31±1 meV), and TO (=43±2 meV) phonons. dominate in the low-temperature luminescence spectra of GaP and In_1–xGa_xP with a small concentration of photon impurities. The complex luminescence band that arises for sufficiently high levels of excitation and at T = 9°K is attributed to the luminescence of an electron-hole drop (EHD). The transformation of spectral form of the EHD band with the transition from GaP to In_1–xGa_xP is attributed to a simultaneous reduction in the contribution of the TA and TO replicas and to the appearance of a phononless component in the luminescence of the EHD.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 9, pp. 37–40, September, 1985.     

The Influence of Annealing in Zinc Vapor on the Visible and Mid-IR Luminescence of ZnSe:Fe2+

Optics and Spectroscopy - The influence of annealing in zinc vapor on the impurity-defect composition and the IR cathodoluminescence (CL) of ZnSe:Te plates diffusion-doped with iron is studied....     

A series of free exciton lines in zinc diarsenide

A structure corresponding to the n=1, 2, and 3 free-exciton states is observed in the optical transmission spectra of zinc diarsenide at 5 K. The band gap for E⊥C at temperatures of 5–300 K and the exciton binding energy (17.5 eV) are determined. Fiz. Tverd. Tela (St. Petersburg) 40, 877–878 (May 1998)