The specially designed ZnSe–ZnTe superlattice (SL), type-II SL, has the light up-conversion effect that SL emits a photoluminescence (PL) peak under the irradiation of the excitation light with the lower energy than the PL peak. The excitation intensity dependence of the energy of up-converted PL peak obeys the characteristic of type-II SL. The PL peak intensity has the super-linear dependence on the excitation intensity. The five kinds of samples in this work showed these phenomena. The model to explain these situations has been proposed.

The photoluminescence (PL) spectra of the type II ZnSe–ZnTe superlattices with dual-subband structures have two emission peaks. The PL peak at the higher energy side appears by the excitation even with the light, with the middle energy between the PL peaks. The emission energy of the up-converted light shows dependence similar to the case of direct excitation (high-energy excitation) on the excitation intensity. The emission energy increases with increase in the excitation intensity. The up-converted and the direct excited emissions are due to the same state in the superlattice.

ZnSe-ZnTe superlattices (SL's) with dual subband structures have been succesfully grown on ZnSe substrates. Those SL's show the so-called light up-conversion effect. The efficiency of the up-conversion has been improved by about 30 times compaired to the SL structures grown on usual GaAs substrate. (C) 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim.

The chromium-doped ZnTe layers were grown by molecular beam epitaxy technology on the GaAs substrates. The metallic chromium was used as a dopant. The characteristic emission of the Cr2+ ions that is incorporated into ZnTe epilayers was obtained. However, the attempt of doping by CrI3 has shown that the halides induce a deterioration of the surface morphology and are inefficient dopants for II-VI semiconductors. (C) 2001 American Vacuum Society.

We have studied MBE-grown CdSe submonolayers (SMLs) using cathodoluminescence (CL) and transmission electron microscopy (TEM). The CdSe SMLs were embedded into ZnSe matrix layer and made to undergo different lattice strains from thick ZnSSe, ZnSe and ZnMgSe cladding layers. It was revealed that the CdSe SML emission line has different energy position and FWHM for the structures with variable cladding layers. This characteristic is attributed to the effect of strain in the ZnSe matrix layer and its surface roughness on the CdSe distribution along the surface. At the deposition of the CdSe SMLs on unstrained flat surface of ZnSe, the homogeneous quantum well (QW)-like CdZnSe alloy layer is formed. Using the strained roughness surface increases fluctuations in the Cd distribution along the surface. While, assuming the compressive ZnSe matrix (ZnSSe cladding layers), the CL line has to be broadening for the CdSe cluster organization only, in the case of structures with ZnMgSe cladding layers, low-energy offset is observed. This is due to the creation of the CdSe ML islands with relatively large lateral size.

Molecular-beam epitaxy was used to grow distributed Bragg mirrors on ZnSe substrates. These mirrors are composed of 10.5 and 20 pairs of alternating quarter-wave ZnMgSe and ZnCdSe layers with reflectance peaks at the wavelengths of 530 and 560 nm, respectively, which fall in the transparency region of the substrate. These structures were studied by low-temperature cathodoluminescence, atomic-force microscopy, and transmission electron microscopy. The maximum of the reflection coefficient was 78% for a 20-pair mirror and 66% for a 10.5-pair mirror. This result is interpreted in terms of a model that takes into account the roughness of the interlayer boundaries.

ZnCdSe/ZnSe multiple quantum well structures (MQW) grown by molecular-beam epitaxy (MBE) on a ZnSe substrate have been studied. A vertical-cavity surface-emitting laser has been fabricated. The active medium consisted of the MQW structure and part of the substrate. The lasing action under longitudinal pump by a scanning electron beam with electron energy E-e from 40 to 70 keV has been obtained. The threshold current density was 60 A/cm(2) at T = 80 K and E-e = 65 keV. The output power was 0.15 W at lambda = 465 nm. The efficiency of the electron excitation and threshold carrier density were estimated. The cavity has exhibited lasing at T = 300 K only from ZnSe, owing to the fact that the optical gain occurred in the substrate. Some approaches to improve characteristics of lasers based on MQW structures grown on ZnSe substrates are discussed.

The method of molecular beam epitaxy on a ZnSe substrate was used to grow a ZnCdSe/ZnSe structure with 115 quantum wells. This structure was made up into a cavity which included part of the substrate. Lasing was excited by longitudinal pumping with a scanning electron beam of Ee = 40 — 70 keV energy. At T = 80 K for Ee = 65 keV the threshold current density was 60 A cm-2 and the output power was 0.15 W at the 465 nm wavelength. At T= 300 K the lasing (λ= 474 nm) occurred in the ZnSe substrate.

ZnCdSe/ZnSe multiple quantum-well (MQW) structures were grown by MBE on ZnSe(0 0 1) substrates prepared by seeded chemical-vapour transport (SCVT) in hydrogen. Scanning force microscopy (SFM) analysis of these structures was performed. A method for the preparation of the substrate surface was found that resulted in a decrease of the root-mean-square (RMS) roughness of the MQW structure surfaces, down to 1 nm. For these structures intense cathodoluminescence (CL) from the QWs was observed. By e-beam pumping a microcavity, pulse lasing was achieved at room temperature (RT).

ZnCdSe/ZnSe quantum wells of different thicknesses are grown by molecular-beam epitaxy on ZnSe(001) substrates. The latter are cut from ZnSe ingots obtained by gas transport in hydrogen. The substrate surface is prepared by colloid-chemical polishing followed by annealing in atomic hydrogen and deposition of a protective selenium film. The surface topography is monitored during epitaxial growth by reflection high-energy electron diffraction (RHEED). The surface microrelief of the samples is examined by atomic force microscopy, and the cathodoluminescence of the quantum-well structures is studied at 40 and 300 K. The relatively low microroughness of the surface, the high-contrast elongated reflections in the diffraction pattern, and the dependence of the spectral position of the quantum-well luminescence line on the well width attest to the high structural quality of the structures grown. (C) 1997 American Institute of Physics.

The thermal stability and luminescence properties of ZnCdSe/ZnSe quantum-well structures grown by molecular-beam epitaxy are investigated. A comparative analysis is made of the photoluminescence spectra of the structures before and after annealing. In the sample spectra after annealing (at 500 °C) a decrease in the intensity of the exciton luminescence line by more than two orders of magnitude, accompanied by an increase in the intensity of the deep levels, is observed. As a result of annealing at a lower temperature (about 400 °C), a narrowing of the exciton luminescence, accompanied by a shift of the maximum toward longer wavelengths, was detected.

Cathodoluminescence (CL), photoreflection (PR), phototransmission (PT) of single and multiquantum wells (MQWs) and strain layer ZnCdSeZnSe superlattices (SLs) grown by molecular beam epitaxy (MBE) were studied. An increase of the Stokes shift with the number of quantum wells (QWs) and the appearance of new lines in CL and PT spectra were observed. Room temperature (RT) vertical-cavity surface-emitting laser (VCSEL) operation was achieved by using the SL structures. Output power up to 2.2 W in single longitudinal mode with λ = 493 nm was obtained. Cut facet laser wavelength of the same SL structure was 502 nm.

We discuss the possibility of lowering the oscillation threshold in semiconductor lasers pumped by an electron beam and consider the prospects of active elements of laser cathode-ray tubes operating at room temperature with the use of multilayer A(II)B(VI) heterostructures.

The use of a broad-bandgap II-VI semiconductors and their ternary and quaternary alloys for vertical-cavity surface-emitting laser (VCSEL) fabrication open a new additional possibilities for their design and applications. In particular, one of the promising using is the realization of a large screen color high definition TV (HDTV) laser projection systems, and flat panel color displays [1,2]. One of the main advantages of the II-VI VCSEL's, in this case, is the possibility of the full color HDTV laser screen creation based only on this materials. The bulk II-VI compounds were used recently for the first successful demonstration of the laser cathode ray tube (LCRT) and color laser TV system [3]. However, one of the limitations of this scheme was the sufficiently high E-beam current threshold, in particular, for the room-temperature operation.

Theoretical and experimental studies of vibrational modes in the (Zn, Cd)Se/ZnSe quantum wells and ZnSe films are presented. The space distribution of electric field accompanying the quasi-transverse vibrations and hence the intensity of corresponding Raman line depends considerably on the thickness of the layers. The quasi-longitudinal vibration and its Raman intensity are insensitive to the thickness. These quasi-transverse and quasi-longitudinal modes give the main contribution to the Raman spectra of the (Zn, Cd)Se/ZnSe quantum wells.

A superlattice with strained ZnCdSe/ZnSe layers was grown by the method of molecular beam epitaxy. This superlattice was used as the active layer in the screen of a laser cathode-ray tube. The room-temperature output power was 1.6 W in the form of one longitudinal mode at the 484 nm wavelength. The earlier results obtained at electron energies below 50 keV were improved.