The luminescence of self-activated and copper-doped zinc selenide

The photoluminescence excitation and emission spectra of crystals of zinc selenide doped with copper or chlorine have been measured. The luminescence studies show that crystals doped with chlorine contain a slight trace of copper contaminant. Since the self-activated emission associated with chlorine and the low-energy copper emission overlap in the red region of the spectrum, it is necessary to remove all traces of copper from a crystal to isolate the self-activated emission. This has been done by heating crystals in molten zinc. In this way it has been possible to show that at 85 °K the self-activated emission band lies at 6150 Å, whereas the copper-red emission occurs at 6400 . The self-activated emission is excited strongly in a band centred at 4850 Å, while the copper-red emission is excited in a band centred at 5100 Å. The various transitions Å involved are discussed.     

Effect of magnesium isovalent impurity on the temperature stability of blue luminescence in zinc selenide

The effect of Mg isovalent impurity on photoluminescence in undoped and Al(donor)-doped ZnSe crystals is investigated. The anomalously weak temperature quenching of the blue band in Mg-containing samples is detected.     

Effect of non-stoichiometry on the occurrence of Er3+ luminescence sites in erbium-implanted zinc selenide

Erbium-implanted ZnSe cubic crystals with a high V_Zn concentration gave luminescence due to Er³⁺ ions at Zn_sub sites (Centre C) but no luminescence due to Er³⁺ ions at Zn_int sites (Centre A) or Se_sub sites (Centre B). On the other hand, Centres A and B were detected in samples with low V_Zn concentrations but Centre C was absent. To detect luminescence due to all three erbium centres moderate V_Zn concentrations were necessary. In such samples post-implantation annealing at 250–325°C caused Er³⁺ ions to occupy Se_sub and Zn_int sites but annealing at 400°C caused Er³⁺ ions to migrate from the Se_sub sites and be detected at Zn_sub sites.     

Edge emission in zinc selenide

Three different series of edge emission bands, associated with donor—acceptor recombination, have been observed at 10 K in crystals of zinc selenide grown in a continuous flow of argon or in sealed capsules in the presence of excess zinc or selenium. It is tentatively suggested that two of these series are associated with random and preferential pairing of the same donors and acceptors.     

Photoluminescence of sodium-implanted zinc selenide

Luminescence measurements indicate that Na acceptors implanted into ZnSe become optically active after annealing at 500°C. The spectra show a strong Na dependence for both the R series band and the I^Y₁ exciton line. In this work Ne-implanted and unimplanted samples were annealed and measured with the Na-implanted material to isolate defect-induced spectral features. Several new bands resulting from radiation damage are reported, along with annealing properties of the defect bands and Na-related luminescence.     

The roles of zinc selenide sandwiched between organic layers and its applications in white light-emitting diodes

In this paper, the roles of zinc selenide (ZnSe) sandwiched between organic layers, i.e. organic/ZnSe/aluminum quinoline (Alq₃), have been studied by varying device structure. A broad band emission was observed from ITO/poly(N-vinylcarbazole)(PVK)(80 nm)/ZnSe(120 nm)/ Alq₃(15 nm)/Al under electric fields and it combined the emissions from the bulk of PVK, ZnSe and Alq₃, however, emission from only Alq₃ was observed from trilayer device ITO/N,N^′-bis-(1-naphthyl)-N,N^′-diphenyl-1, 1^′-biphenyl-4, 4^′-diamine (NPB) (40 nm)/ZnSe(120 nm)/ Alq₃(15 nm)/Al. Consequently the luminescence mechanism in the ZnSe layer is suggested to be charge carrier injection and recombination. By thermal co-evaporating Alq₃ and 4-(dicyanomethylene)-2-t-butyl-6-(1,1,7,7-tetramethyljulolidyl-9-enyl)-4H-pyran (DCJTB), we get white light emission with a Commission Internationale de l’E clairage (C.I.E) co-ordinates of (0.32, 0.38) from device ITO/PVK(80 nm)/ZnSe(120 nm)/ Alq₃:DCJTB(0.5 wt% DCJTB)(15 nm)/Al at 15 V and the device performs stably with increasing applied voltages.     

Conductivity peculiarities in epitaxial layers of cadmium selenide

Electrophysical properties are studied in epitaxial cadmium selenide films produced by condensation on common mica and fluorophlogopite substrates over a wide range of substrate temperatures (T_s). It is shown that under conditions close to equilibrium highly perfect layers are produced with charge carrier mobility up to 300 cm²/V · sec and concentration ～ 10¹⁶ cm^?3. The temperature dependence of carrier concentration and mobility are studied in undoped and doped CdSe films. The values of the intercrystallite energy barriers are determined in layers condensed at differing T_s. It is shown that at T_s>630?C the charge carrier diffusion mechanism is close to that of a monocrystal, while for a barrier diffusion mechansim (T_s<630?C) the character of the energy barriers for the cubic and hexagonal phases in CdSe is somewhat different. Donor-level ionization energy and ionized center concentration are determined.     

Thermal conductivity of polycrystalline zinc selenide

The thermal conductivity of optically transparent zinc selenide polycrystals fabricated by vapor deposition was experimentally studied in the temperature range 80–400 K in the as-deposited state and after deformation along the crystal growth direction followed by recrystallization. In the low-temperature range, textured ZnSe samples exhibit anisotropy of the thermal conductivity, which also persisted after their deformation and recrystallization. The anisotropy of the thermal conductivity is caused by phonon scattering by dislocations oriented along the crystal growth direction. The thermal conductivity of ZnSe at T>270 K is shown to be limited by the scattering of acoustic phonons by optical phonons.     

Cathodoluminescence of laser-annealed erbium-implanted zinc selenide

After zinc selenide crystals implanted with erbium ions had been annealed with a continuous wave (cw) krypton ion laser it was found that the cathodoluminescence emission intensity of the implanted erbium ions had been considerably enhanced. In order to gain some understanding of the physical processes involved in such an enhancement a comparison was made between thermal annealing and laser annealing of the implanted crystals. Clear differences were found in the cathodoluminescence spectra of the thermally annealed and laser-annealed samples. The increase in cathodoluminescence emission intensity produced by laser annealing was attributed to the production of selenium vacancies in the vicinity of the implanted erbium ions and leads us to suggest the possibility of site selective annealing by this technique.     

Luminescence of tungsten centers in zinc selenide

Luminescence spectra of W centers in ZnSe are studied. Radiative d–d transitions are identified by the Tanabe–Sugano diagram of the crystal field theory. It is found that the type of electronic transitions changes with a significant change in spectral characteristics of impurity radiation during the transition fromthe 3d- to 5d-electronic systemof impurity centers in the crystals under study.     

Piezoelectric textures of polycrystalline zinc selenide

The preliminary results of an investigation of the structure and electrophysical properties of CVD-grown polycrystalline ZnSe are reported. A weak multicomponent texture is observed which bears upon the piezoelectric effect, the characteristic features of the electric polarization, and the characteristic elastic oscillations of samples of regular shape. Zh. Tekh. Fiz. 69, 141–143 (February 1999)     

Postgrowth residual stresses in polycrystalline zinc selenide

The residual stresses in samples of polycrystalline ZnSe are studied by measuring the photoelasticity in the visible part of the spectrum with transillumination parallel and perpendicular to the growth axis. The thermal and growth components of the birefringence, which exhibit different types of distributions among samples, are investigated. It is established that the thermal component has a nearly equilibrium distribution, while the growth component has an asymmetric distribution, which reflects individual features in the growth of each specific sample. Zh. Tekh. Fiz. 68, 85–90 (June 1998)     

Excitons bound at oxygen centers in zinc selenide

Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 11, pp. 67–72, November, 1989.     

Infrared radiation of zinc selenide single crystals

Long-wave photoluminescence (PL) spectra of both as-grown and Au-doped n-ZnSe single crystals are studied in the temperature range from 81 to 300 K. A narrow band of infrared (IR) radiation centered at 878 nm (1.411 eV) manifests itself in the low-temperature PL spectrum. It is established that this band intensity first increases and then decreases with increasing concentration of doping impurity. With increasing excitation radiation intensity, spectral position of the IR PL band is unchanged and its intensity increases under the linear law. With increasing excitation radiation wavelength, the IR PL band intensity increases, it becomes narrower and shifts towards long wavelengths. It is shown that the observed IR radiation is caused by recombination of free electrons with holes localized on associative acceptors in the ZnSe:Zn:Au crystals or in the undoped crystals.