Oleg Maksimov

Patterned three-color ZnCdSe/ZnCdMgSe quantum-well structures for integrated full-color and white light emitters

We report the growth and characterization of patterned ZnCdSe/ZnCdMgSe quantum-well (QW) structures grown adjacent to each other on a single InP substrate. Each structure emits at a different wavelength range spanning the visible range. Stripe and square-shaped QW structures of different emission wavelengths, with lateral dimensions between 15 and 60 μm, were deposited sequentially by shadow mask selective area epitaxy (SAE) steps. Conventional and microphotoluminescence measurements were used to characterize the patterned QWs. They exhibit well-defined excitonic emission in the red, yellow, and green regions of the visible spectrum. This result demonstrates the feasibility of fabricating integrated full-color light emitting diode and laser-based display elements and white light sources using the ZnCdMgSe material system and shadow mask SAE.

Growth and characterization of BeCdSe alloys and BeCdSe/ZnCdMgSe quantum wells on InP substrates

We report the molecular-beam-epitaxy growth and characterization of BexCd1−xSe (0.06<x<0.2) epilayers and Be0.08Cd0.92Se/Zn0.32Cd0.25Mg0.43Se quantum-well (QW) structures on InP substrates. Good optical properties and high crystalline quality were established using photoluminescence and x-ray diffraction measurements. Narrow x-ray rocking curves with line widths down to 49 arc sec were obtained for Be0.2Cd0.8Se, closely lattice-matched to InP. A strong luminescence emission with energy of 2.072 eV and a full width at half maximum of 27 meV at 77 K was obtained from a QW structure with a 48-A-thick QW. Strong room-temperature luminescence was also observed from the QW. A linear dependence of the QW photoluminescence intensity on the excitation laser density and an absence of shift in the emission energy indicates that the QW emission has an excitonic behavior. Based on these results and on the expected lattice-hardening properties of BeSe, we propose that BeCdSe is an attractive quantum-well material for v...

High crystalline quality ZnBeSe grown by molecular beam epitaxy with Be-Zn co-irradiation

High crystalline quality ZnBeSe epilayers with di!erent compositions were grown on GaAs substrates by molecular beam epitaxy using Be}Zn co-irradiation of the III}V surface and a ZnSe bu!er layer. A (1]2) re#ection high-energy electron di!raction pattern was formed after the Be}Zn co-irradiation indicating the formation of Be and Zn dimers on the GaAs surface. A two-dimensional growth mode was observed throughout the growth of the ZnSe bu!er layer and ZnBeSe epilayer. Narrow X-ray linewidth as low as 23 arcsec with the etch pit density of mid 104 cm~2 were obtained. The linewidth of the dominant excitonic emission is about 2.5 meV at 13 K for the near-lattice-matched ZnBeSe layer. For a nitrogen-doped sample, capacitance}voltage measurements showed a net acceptor concentration of 2.0]1017 cm~3. In addition, the use of a BeTe bu!er layer and of a Zn-irradiation with a ZnSe bu!er layer were also investigated. ( 2000 Elsevier Science B.V. All rights reserved.

Distributed Bragg reflectors based on (Zn, Cd, Mg)Se for use in the visible spectral range

Distributed Bragg reflectors (DBRs) based on ZnCdSe and ZnCdMgSe quarter wave layers have been grown on InP (001) substrates by molecular beam epitaxy. Their reflectivity maxima were controlled by the individual thicknesses of constituent layers, and were adjusted in the range of 615–500 nm, covering the red, green, and blue-green regions of the visible spectrum. The crystal quality of the structures was assessed by double crystal x-ray diffraction measurements. Reflectivity as high as 95% was achieved for the DBR structures that consisted of 16 periods. Theoretical calculations, based on the transfer matrix method, predict that a reflectivity above 99% can be achieved by increasing the number of periods to between 20 and 26.

Distributed Bragg reflectors for visible range applications based on (Zn,Cd,Mg)Se lattice matched to InP

Lattice-matched (Zn,Cd,Mg)Se epilayers were grown by molecular-beam epitaxy on InP substrates. X-ray diffraction and photoluminescence measurements show the high crystalline quality of the epilayers. Using a prism coupler technique, the index of refraction of the epilayers was investigated at four discrete wavelengths. With these results, (Zn,Cd,Mg)Se-based distributed Bragg reflector structures have been grown, covering nearly the entire visible spectral range. A maximum reflectivity of 95% has been achieved for structures having 16 periods.

Be-Chalcogenide Alloys for Improved R-G-B LEDs: BexZnyCd1–x–ySe on InP

We report the molecular beam epitaxy growth and characterization of Be x Zn y Cd 1-x-y Se (x ≤ 0.2) layers on InP substrates. Good optical properties and high crystalline quality were established using photoluminescence and X-ray diffraction measurements. The dependence of the Be x Cd 1-x Se band gap energy on composition was investigated and fit to the quadratic equation: Eg = 1.78(1 - x) + 5.6x - 2.6x(1 - x) with a bowing parameter of 2.6 eV. Our results indicate that Be x Zn y Cd 1-x-y Se is an attractive quantum well material for application in visible light emitters.

Temperature Dependence of the Band-Edge Transitions of ZnCdBeSe

We have characterized the temperature dependence of band-edge transitions of three (Zn0.38Cd0.62)1-xBexSe II–VI films with different Be concentrations x by using contactless electroreflectance (CER) and piezoreflectance (PzR) in the temperature range of 15 to 450 K. By a careful comparison of the relative intensity of PzR and CER spectra, the identification of light-hole (lh) and heavy-hole (hh) character of the excitonic transitions of the samples has been accomplished. The temperature dependence analysis yields information on the parameters that describe the temperature variations of the energy (including thermal expansion effects) and broadening parameter of the band edge transitions of ZnCdBeSe. The study shows that Be incorporation can effectively reduce the rate of temperature variation of the energy gap.

Red–green–blue light emitting diodes and distributed Bragg reflectors based on ZnCdMgSe lattice-matched to InP

Abstract Wide bandgap II–VI materials and structures based on ZnCdMgSe alloys lattice matched to InP substrates have been investigated. Quantum well (QW) structures designed to emit throughout the entire visible spectral range were constructed by varying the QW layer thickness and/or composition. Light emitting diode (LED) structures were grown, fabricated and tested. Electroluminescence emission in the blue, green, yellow and red regions of the visible spectral range were obtained from lattice-matched or pseudomorphic structures that varied only in the composition or thickness of the QW layer. Lattice-matched distributed Bragg reflector (DBR) structures with reflectivity maxima in the red, green and blue were also grown and characterized. Since the LED and DBR structures are made from the same materials it should be possible to combine these into a single structure for the design of high performance LEDs and vertical cavity surface emitting lasers that operate in the entire visible range.

Continuous-wave and passively mode-locked operation of a cunyite (Cr 4+ :Ca 2 GeO 4 ) laser

Continuous-wave and mode-locked Cr(4+):Ca(2)GeO(4) lasers that use a fiber laser pump source were demonstrated. The continuous-wave Cr(4+):Ca(2)GeO(4) laser yielded a maximum output power of 415 mW at 1420 nm and a tuning range of 1335-1492 nm. With a saturable-absorber mirror, 60-ps pulses and 110-mW maximum output power were generated from a passively mode-locked Cr(4+):Ca(2)GeO(4) laser.

Properties of MBE-Grown ZnBeSe: Study of Be Isoelectronic Traps and of Dopant Behavior

In this paper we present studies on undoped, Cl-doped, and N-doped ZnBeSe using photoluminescence (PL). We show that the dominant PL from undoped samples is effective mass type and suggest that it is of isoelectronic origin. We also show that the binding energy of both donor and acceptor impurities increases with Be concentration.