Theoretical investigation of new MgS-ZnSe structures

International audienceheoretical studies of the excitonic properties for different designs of MgS-ZnSe structures are presented. Excitonic binding energies are calculated for single quantum wells. For MgS-ZnSe superlattices, the energy of electron-hole transitions are evaluated and compared with the experimental photoluminescence spectra

Performance simulation of interband laser diodes grown on InAs substrate

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Quantum confined Stark effect due to built-in internal polarization fields in (Al,Ga)N/GaN quantum wells

(Al,Ga)N/GaN quantum wells have been studied by temperature-dependent luminescence and reflectivity. The samples were grown by molecular beam epitaxy on (0001) sapphire substrates, and well widths were varied from 3 to 15 monolayers (ML's) with a 2-ML increment, thus providing a reliable data set for the study of the well width dependence of transition energies. The latter shows a strong quantum confined Stark effect for wide wells, and an internal electric-field strength of 450 kV/cm is deduced. X-ray diffraction performed on the same samples shows that the GaN layers are nearly unstrained, whereas the (AI,Ga)N barriers are pseudomorphically strained on GaN. We conclude that the origin of the electric field is predominently due to spontaneous polarization effects rather than a piezoelectric effect in the well material. [S0163-1829(98)50944-7]

Extremely sharp dependence of the exciton oscillator strength on quantum-well width in the GaN/AlxGa1-xN system: The polarization field effect

Exciton reflectivity from GaN/AlxGa1-xN quantum wells (QWs) shows broad peaks that are difficult to analyze within a conventional single-free-exciton model. We have applied a new formalism that allows us to separate numerically radiative and inhomogeneous broadenings of an exciton resonance comparing the Fourier-transformed reflection spectra with calculated time-resolved reflectivities. We have found the exciton oscillator strength to decrease dramatically with the increase of the QW width in GaN/Al0.07Ga0.93N system. The collapse of the oscillator strength is a manifestation of the polarization field effect, as confirmed by our variational calculation. We find that only excitons in very thin quantum wells have an oscillator strength exceeding that of the exciton in bulk GaN

Quantum confined Stark effect due to built-in internal polarization fields in (Al,Ga)N/GaN quantum wells.

International audience(Al,Ga)N/GaN quantum wells have been studied by temperature-dependent luminescence and reflectivity. The samples were grown by molecular beam epitaxy on (0001) sapphire substrates, and well widths were varied from 3 to 15 monolayers (ML’s) with a 2-ML increment, thus providing a reliable data set for the study of the well width dependence of transition energies. The latter shows a strong quantum confined Stark effect for wide wells, and an internal electric-field strength of 450 kV/cm is deduced. X-ray diffraction performed on the same samples shows that the GaN layers are nearly unstrained, whereas the (Al,Ga)N barriers are pseudomorphically strained on GaN. We conclude that the origin of the electric field is predominently due to spontaneous polarization effects rather than a piezoelectric effect in the well material

Optical and structural properties of AlGaN/GaN quantum wells grown by molecular beam epitaxy

AlGaN/GaN quantum well (QWs) were grown on (0001) sapphire substrates by molecular beam epitaxy (MBE) using ammonia as nitrogen precursor. The Al composition in the barriers was varied between 8 and 27 % and the well thickness from 4 to 17 monolayers (MLs, 1ML = 2.59 Angstrom). X-ray diffraction (XRD) experiments are used to investigate the strain state of both the well and the barriers. The QW transition energy are measured by low temperature photoluminescence (PL). A large quantum confined Stark effect is observed leading to QW luminescence much lower than the emission line of the GaN buffer layer for well width above a certain critical thickness. The built-in electric field responsible for such a phenomenon is deduced from fit of the PL data. Its magnitude is of several hundred kV/cm and increases linearly with the Al composition