Showing papers by "E. Muñoz published in 1992"

Photoluminescence characterization of gated pseudomorphic AlGaAs/InGaAs/GaAs modulation‐doped field‐effect transistors

Abstract: Electric field effects on gated pseudomorphic AlGaAs/InGaAs/GaAs quantum wells, where the Fermi level is modulated with a reverse gate voltage, are studied by low‐temperature photoluminescence. A fit of the measured transition energies, with a self‐consistent solution of the coupled Schrodinger–Poisson equations, gives the Fermi energy and the sheet carrier density. The absolute and relative intensities, from the first and second electron subbands to the first‐hole subband transitions, are analyzed as a function of the carrier density and the Fermi level position. A very good agreement is found between data and calculations. No photoluminescence intensity enhancement, assigned to the Fermi‐energy‐edge singularity effects, has been observed.

Photoluminescence and Raman analysis of strain and composition in InGaAs/AlGaAs pseudomorphic heterostructures

Abstract: Photoluminescence and Raman spectroscopy have been used to determine composition and strain in pseudomorphic InxGa1-xAs/AlxGa1-yAs quantum wells. Series of MBE-grown samples, comprising bulk-relaxed InxGa1-xAs reference layers and InxGa1-xAs/AlyGa1-yAs quantum wells of different thicknesses, were considered. Photoluminescence transitions in the strained structures were analysed using a semiempirical model including strain and composition effects in the InxGa1-xAs well. The GaAs-like longitudinal optical LO phonon Raman shift allowed an independent strain estimation. The agreement between photoluminescence and Raman results confirms the assumption that there is no relaxation in the wells. The effects of uncertainties in the stress deformation potentials and phonon coefficients on strain determination have been discussed. The authors' results show that photoluminescence is an adequate tool to characterize InGaAs strained layers.

DX centre characterization in Se-doped AlGaAs under hydrostatic pressure

Abstract: Se-related DX centres in AlGaAs alloys have been characterized by deep-level transient spectroscopy techniques under hydrostatic pressure. The thermal-emission energy, Ee=0.24 +or-0.02 eV, is constant throughout the alloy range considered (0.29

DX center electron occupancy under hydrostatic pressure in Si‐doped Iny(Ga1−xAlx)1−yAs alloys

Abstract: DX centers in In‐mixed AlGaAs alloys are analyzed by deep level transient spectroscopy and capacitance vs temperature measurements. The addition of In to Si‐doped AlGaAs, with x=0.21 and 0.30, shifts the Si‐DX center to a shallower position. Under hydrostatic pressure, DX centers deepen again into the band gap. The DX center shift, and consequently, the reduction of the DX center electron occupancy, when In is added, is due to an increase of the Γ to L energy difference. In terms of band‐gap energy and DX center depth, adding 1% In is equivalent to a 1% Al reduction. Then, In mixing does not offer any new benefit to minimize DX center effects in AlGaAs‐based heterojunction devices.