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GaN films are grown on [0 0 1] GaAs substrates by plasma-assisted molecular beam epitaxy using a three-step process that consists of a substrate nitridation, deposition of a low-temperature buffer layer, and a high-temperature overgrowth. X-ray diffraction and transmission electron microscopy indicate that this method promotes prismatic growth of c-oriented α-GaN. Photoluminescence studies show that the emission from cubic β-GaN inclusions dominates the spectrum.

BexZn1−xTe thin films were grown on InP substrates by molecular beam epitaxy (MBE). Optical properties of the epilayers were studied using reflectance and photoluminescence (PL) measurements. An increase in the full width at half maximum of the emission line with the increase in BeTe content was observed and explained by the disorder-induced broadening. The temperature dependence of the band gap energy was determined from reflectance spectra and fitted by semiempirical equation taking into account average phonon energy and electron–phonon interaction. A reduction of the temperature variation of the band gap with the increase in BeTe content was observed. We propose that this effect is due to the decrease of the lattice contribution caused by the lattice hardening properties of BeTe.

We report photoluminescence and reflectivity measurements of Mg x Zn y Cd 1-x-y Se epitaxial layers (0 0.3), we observe an anomalous temperature dependence of both the emission energy and line broadening. This behavior is assigned to the emission from localized states. Different mechanisms of carrier localization are discussed and exciton localization on statistical CdSe clusters is proposed to be the most likely one.

We report photoluminescence (PL) and reflectivity measurements of Zn0.5Cd0.5Se epilayers grown by molecular beam epitaxy on InP substrates. The low-temperature PL spectra are dominated by asymmetric lines, which can be deconvoluted into two Gaussian peaks with a separation of ,8 meV. The behavior of these peaks is studied as a function of excitation intensity and temperature, revealing that these are free exciton (FE) and bound exciton emission lines. Two lower energy emission lines are also observed and assigned to the first and second longitudinal optical phonon replicas of the FE emission. The temperature dependence of the intensity, line width, and energy of the dominant emission lines are described by an Arrhenius plot, a Bose ‐ Einstein type relationship, Varshni’s and Bose ‐Einstein equations, respectively.

We present photoluminescence (PL) studies of Cl-doped Zn1−xBexSe (x=0–0.029) alloys performed in wide ranges of temperature (10– 296 K ) and of excitation intensities. We show that the high-temperature PL is characterized by a free-to-acceptor-type transition, involving shallow state of the localized holes. We shall show that similar transitions are also present in comparable undoped samples, but the PL intensity is substantially lower. Finally, we show that the ionization energy of the relevant acceptor-like species increases with Be concentration, suggesting an effective mass type defect.

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.

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.

We report the optical properties of BeCdSe/ZnCdMgSe single quantum well (QW) structures that consist of closely lattice matched ZnCdMgSe barrier layers and a strained BeCdSe QW layer (Δa/a=1.95%) grown on InP substrates. Emission from the red to the green regions of the visible spectrum was obtained from the structures with the QW thickness varying from 95 to 12 A. Efficient QW emission, dominated by an exciton recombination behavior, was observed. From the Arrhenius plot of the integrated emission intensity as a function of temperature, an activation energy of 61 meV was obtained for a BeCdSe QW structure with a 48 A thick QW layer. Parameters that describe the temperature dependence of the near band edge emission energy and the broadening of the excitonic emission were evaluated. Our results indicate that the BeCdSe-based QW structures are attractive for application as red light emitters.

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.

We annealed ZnSe/GaAs heterostructures in the oxygen atmosphere and investigated structural and optical properties of the forming films using X-ray diffraction and photoluminescence. While highly textured ZnO films were synthesized via low-temperature processing (~ 500 °C), high temperature processing (~ 800 °C) promoted reaction at the film/substrate interface and Zn loss from the film surface resulting in the polycrystalline ZnGa 2 O 4 and ZnO 2 .

We report photoluminescence (PL) study of Be x Cd 1− x Se epitaxial layers ( x

We have studied photoluminescence (PL) of ZnSe samples codoped with Te and N in δ-layers. We have concluded that Te clusters are involved in the PL. We also compared the PL data of samples with lower Te concentrations to those with higher Te concentrations; the results corroborate the Te-cluster conclusion.

We have investigated the growth and optical properties of a set of BexZn1−xTe epitaxial layers having different composition, with x ranging from 0–0.7. Comparison of the reflectivity and the photoluminescence spectra allowed us to locate the direct-to-indirect band gap crossover for this alloy at x≈0.28. The Γ→Γ direct band gap exhibits a linear dependence on composition over the entire compositional range and can be fitted to the equation EgΓ(x)=2.26*(1−x)+4.1*x. It increases linearly with BeTe content at a rate of 18 meV for a change of 1% in BeTe content. The Γ→X indirect band gap for BexZn1−xTe can be fitted to the equation EgX(x)=3.05*(1−x)+2.8*x−0.5*x*(1−x), suggesting that the energy of the indirect Γ→X transition for ZnTe is about 3.05 eV.

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.

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.

was introduced in submonolayer quantities via planar doping during molecular beam epitaxy. Here, we examine the mechanism of this improved doping. We show that it resides in the formation of ZnTe-rich nanoislands, with the N embedded in these. This result is obtained by studies involving transmission electron microscopy, high-resolution x-ray diffraction, secondary-ion mass spectroscopy, and temperature quenching of photoluminescence. We note that these nanoislands appear quite unique, in providing doping of semiconductors, and thus are of great interest of their own.

A detailed optical characterization of a Bridgman-grown wurtzite- (WZ-) type Be0.075Cd0.925Se mixed crystal and three zinc-blende (ZB) BexCd1−xSe epilayers grown by MBE on InP substrates has been carried out via photoluminescence (PL) and contactless electroreflectance (CER) in the temperature range of 15–400 K. The PL spectrum of the WZ-BeCdSe at low temperature consists of an exciton line, an edge emission feature due to recombination of donor–acceptor pairs, and a broad band related to recombination through deep-level defects, while the PL emission peaks of the ZB-BeCdSe epilayers show an asymmetric shape with a tail on the low-energy side. Various interband transitions, originating from the band edge and spin–orbit splitting critical points, of the samples have been observed in the CER spectra. The peak positions of the exciton emission lines in the PL spectra correspond quite well to the energies of the fundamental transitions determined from electromodulation data. The parameters that describe the temperature dependence of the fundamental and spin split-off bandgaps and the broadening function of the band-edge exciton are evaluated and discussed.

The effects of Be on the II–VI/GaAs interface and on CdSe quantum dot (QD) formation were investigated. A (1×2) surface reconstruction was observed after a Be–Zn coirradiation of the (001) GaAs (2×4) surface. ZnBeSe epilayers grown after the Be–Zn coirradiation show very high crystalline quality with x-ray rocking curve linewidths down to 23 arcsec and a low etch pit density of 4×104 cm−2, and good optical quality with a band-edge photoluminescence (PL) emission peak linewidth of 2.5 meV at 13 K. However, ZnBeSe epilayers grown after Zn irradiation alone have poor crystalline quality and poor optical properties. Atomic force microscopy measurements show that CdSe QDs grown on ZnBeSe have higher density and smaller size than those grown on ZnSe. A narrower PL emission peak with higher emission energy was observed for the CdSe QDs sandwiched by ZnBeSe. These results indicate that the formation of CdSe QDs as well as the II–VI/GaAs interface are modified by the presence of Be.