Valence band parameters of cubic zinc selenide derived from magnetoreflectance of the Γ6 − Γ8 exciton

Magnetoreflectance measurements on the Γ₆ ? Γ₈ free exciton ground state in cubic ZnSe in magnetic fields up to 18 Tesla are reported. The diamagnetic shift rate of the ground state components: $\text{|}\text{3}\text{2}\text{>β}$, $\text{|?}\text{3}\text{2}\text{>α}$, $\text{|}\text{1}\text{2}\text{>β}$ and $\text{|?}\text{1}\text{2}\text{>α}$ yield γ₂ = 0.53 ± 0.07 and an exciton reduced mass μ₀ = 0.117 ± 0.003, corresponding to γ₁ = 2.30 ± 0.45 for m_e¹ = 0.16 m₀. γ₁, γ₂ and an effective hole g-value $\text{κ}\text{tilde}\text{= -0.21}$ yield γ₃ = 0.82 ± 0.16 in the parabolic approximation and in agreement with the observed splitting of the $\text{|?}\text{3}\text{2}\text{>α}$, $\text{|?}\text{1}\text{2}\text{>β}$ states for B ∥ [110]. Taking into account polaron effects we derive bare valence band parameters γ₁^L = 2.71 ± 0.60, γ₂^L = 0.63 ± 0.09 and γ₃^L = 0.97 ± 0.21 from the renormalized parameters γ_i. The present results are considerably smaller than earlier theoretical calculations suggest, however they are in good agreement with a recent detailed analysis of two-photon absorption data for 2P exciton states.     

Shallow acceptor bound exciton and free exciton states in high-purity zinc telluride

We investigated excitons bound to shallow acceptors in high-purity ZnTe and measured excitation spectra of two-hole luminescence lines at 1.6 K using a tunable dye-laser. The electron-hole coupling in the bound exciton (BE) states appears to be very different for the various acceptors even for almost identical exciton localisation energies. Three different types of BE are reported. For the Li-acceptor BE we observe three sub-components separated by 0.22 and 0.17 meV and interpreted as J = $\text{1}\text{2}$, $\text{3}\text{2}$, $\text{5}\text{2}$ states. The Ag-acceptor BE exhibits a strong ground state and a weak excited state at 1.3 meV higher energy. For the as yet unidentified k-acceptor we observe a single BE level, degenerate with the Ag-acceptor BE ground state. Dips in the excitation spectra due to absorption into free exciton 1S, 2S, and 3S states yield an exciton Rydberg R₀ = 12.8±0.3 meV and a free exciton binding energy FE(1S) = 13.2±0.3 meV.     

Indium antimonide energy band parameters derived from diamagnetic exciton spectra

The oscillatory absorption edge spectrum of thin InSb crystals in which the discrete structure of the Wannier-Mott exciton had been revealed at H=0 for the first time has been studied at 1.8 K in magnetic fields of up to 80 kOe. The experimental data were analyzed with a computer taking into account the exciton nature of the phenomenon and the effect on the Landu levels of the nonlocality of potential resulting from the electron-electron exchange interaction. A set of band parameters has been obtained providing a minimum discrepancy between the theoretical and experimental spectra by not more than 0.65 meV per point: $\text{E}{}_{\mathrm{p}}\text{= 23.42 eV, F = -1.18, N}{}_1\text{= -0.33,}\text{r}{}_1\text{= 36.41,}\text{r}{}_2\text{= 15.95,}\text{r}{}_3\text{= 16.99,}\text{r}\text{= 15.22, q = 0.31}$ for $\text{h}\text{= 17.9}$. The reasons for and the extent of discrepancy between the InSb parameters derived by other authors from interband magnetoabsorption experiments are discussed.     

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)     

Optical properties of zinc telluride with cadmium telluride submonolayers

Reflection, luminescence, and Raman spectra of epitaxial ZnTe layers nominally incorporating double CdTe submonolayers were studied. The band of an exciton localized at the potential produced by narrow-gap planar inclusions dominated the luminescence of these heterostructures. The emission parameters of localized excitons (specifically, the ratio of integral emission intensity to localization energy) were determined, and it was found that excitons interact with longitudinal optical phonons of the layer enriched with cadmium. Giant amplification of the Stokes component resonant with the localized exciton level was observed in Raman scattering.     

Structure of the free exciton luminescence band of heteroepitaxial ZnSe/GaAs layers

The exciton reflectance and photoluminescence spectra of epitaxial ZnSe/GaAs layers with a thickness of 2–4 μm are investigated in the temperature range 10–120 K. It is shown that one of the causes of the formation of the doublet structure of the A _n=1 photoluminescence band is interference of the exciton radiation at the boundaries of the near-surface dead layer. Fiz. Tverd. Tela (St. Petersburg) 40, 881–883 (May 1998)     

Collective potential and mass parameters derived from the generator coordinate method

The collective hamiltonian for the axial quadrupole vibrations was derived from theQQ+PP model. The generator coordinate method was applied and the results obtained through the symmetric moments expansion and the gaussian overlap approximation were compared. It was found that the collective potential and the average magnitude of the mass parameter obtained in both approximations are close to each other.     

Copper and native defects in zinc telluride

Zinc telluride crystals were grown from tellurium-rich solutions containing 10¹⁷–10²⁰ cm^?3 atoms of copper. The copper concentrations in these crystals were measured by activation analysis. Hall effect and resistivity measurements were performed. Photoluminescence spectra were also determined. Our interpretation of the different results is that copper brings about both acceptor defects Cu_Zn with a 0·12–0·13 eV ionization energy, and donor defects. The second acceptor level of the zinc vacancy was found to be at 0·15 eV.     

Sm富勒烯的价带光电子能谱

用紫外光电子能谱和同步辐射光电子能谱研究了Sm掺杂C₆₀薄膜的价带电子结构.Sm的价电子大部分转移给C₆₀，化学键以离子性为主.对于任何化学配比都没有观察到费米边，所以Sm富勒烯超导相在室温下为半导体性质.获得了很接近单相Sm_2.75C₆₀的样品在费米能级附近的电子态密度分布.固溶相的光电子发射与Sm_2.75C₆₀有明显区别.Sm_xC_{60关键词： 60}的Sm填隙化合物')" href="#">C₆₀的Sm填隙化合物 价带光电子能谱 电子结构     

Dependence of the heavy-hole exciton reduced mass on quantum-well size in InGaAs/GaAs heterostructures

We present low temperature photoluminescence investigations of the exciton ground state of In_0.14Ga_0.86As/GaAs quantum wells (QW) in the presence of pulsed magnetic fields up to 50 T. The exciton in-plane reduced mass and the heavy-hole in-plane mass are determined from the best fit of theoretical calculations to the magnetic field dependence of PL peaks. When the QW thickness decreases, their masses increases due to valence-band mixing effect.     

Diffusion and lattice location of lithium in zinc telluride

The diffusion of Li in ZnTe has been investigated in the temperature range 400–700°C by use of nuclear analysis and chemical or ion beam etching techniques. The penetration profiles are complex and most of them were found to show three regions. The experimental results are interpreted as a superposition of different diffusion mechanisms: one where the impurity diffuses simultaneously in substitutional and interstitial forms, the interstitial form being trapped at defects, and the other which involves short-circuit paths. Activation energies and diffusion constants D_o were measured. Furthermore the channeling technique was used for lattice location. This revealed that (60–80)% of the lithium atoms occupy the zinc substitutional site following annealing at 500°C.