Binding energies of excitons in II-VI compound-semiconductor based quantum well structures

We present a brief description of the calculation of the variation of the binding energy of the heavy-hole exciton as a function of well width in quantum well structures composed of II-VI compound semiconductors including the effects of exciton-optical phonon interaction as formulated by Pollmann and Büttner [J. Pollmann and H. Büttner, Phys. Rev. B 16, 4480 (1977)], and of particle masses and dielectric mismatches between the well and the barrier layers. We compare the results of our calculations with the available experimental data in ZnSe/MgS, ZnSe/Mg0.15Zn0.85Se, and ZnS/Mg0.19Z0.81S quantum well structures and find a good agreement. © 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim

Determination of energy-band offsets between GaN and AlN using excitonic luminescence transition in AlGaN alloys

We report the determination of the energy-band offsets between GaN and AlN using the linewidth (full width at half maximum) of an extremely sharp excitonic luminescence transition in Alx Ga1-x N alloy with x=0.18 at 10 K. Our sample was grown on C -plane sapphire substrate by metal-organic chemical-vapor deposition at 1050 °C. The observed value of the excitonic linewidth of 17 meV is the smallest ever reported in literature. On subtracting a typical value of the excitonic linewidth in high-quality GaN, namely, 4.0 meV, we obtain a value of 13.0 meV, which we attribute to compositional disorder. This value is considerably smaller than that calculated using a delocalized exciton model [S. M. Lee and K. K. Bajaj, J. Appl. Phys. 73, 1788 (1993)]. The excitons are known to be strongly localized by defects and/or the potential fluctuations in this alloy system. We have simulated this localization assuming that the hole, being much more massive than the electron, is completely immobile, i.e., the hole mass is treated as infinite. Assuming that the excitonic line broadening is caused entirely by the potential fluctuations experienced by the conduction electron, the value of the conduction-band offset between GaN and AlN is determined to be about 57% of the total-band-gap discontinuity. Using our model we have calculated the variation of the excitonic linewidth as a function of Al composition in our samples with higher Al content larger than 18% and have compared it with the experimental data. We also compare our value of the conduction-band offset with those recently proposed by several other groups using different techniques. © 2006 American Institute of Physics

Optical studies of molecular beam epitaxy grown GaAsSbNGaAs single quantum well structures

In this work, the authors present a systematic study on the variation of the structural and the optical properties of GaAsSbNGaAs single quantum wells (SQWs) as a function of nitrogen concentration. These SQW layers were grown by the solid source molecular beam epitaxial technique. A maximum reduction of 328 meV in the photoluminescence (PL) peak energy of GaAsSbN was observed with respect to the reference GaAsSb QW. 8 K and RT PL peak energies of 0.774 eV (FWHM of ∼25 meV) and 0.729 eV (FWHM of ∼67 meV) (FWHM denotes full width at half maximum) corresponding to the emission wavelengths of 1.6 and 1.7 μm, respectively, have been achieved for a GaAsSbN SQW of N∼1.4%. The pronounced S -curve behavior of the PL spectra at low temperatures is a signature of exciton localization, which is found to decrease from 16 to 9 meV with increasing N concentration of 0.9%-2.5%. The diamagnetic shift of 13 meV observed in the magnetophotoluminescence spectra of the nitride sample with N∼1.4% is smaller in comparison to the value of 28 meV in the non-nitride sample, indicative of an enhancement in the electron effective mass in the nitride QWs. Electron effective mass of 0.065 mo has been estimated for a SQW with N∼1.4% using the band anticrossing model. © 2007 American Vacuum Society

Binding Energies Of Excitons In Ionic Quantum Well Structures

We have calculated the binding energies of excitons in quantum well structures based on ionic semiconductors by including the electron-hole interactions with the longitudinal optical phonon field. We have taken into account these interactions by using different effective interaction potentials between the electron and the hole as derived by Haken, by Aldrich and Bajaj, and by Pollman and Büttner. We have calculated the binding energies of excitons in several ionic quantum well structures as functions of well width using these effective potentials by following a variational approach. We find that the values of the exciton binding energies calculated using these potentials are always larger than those obtained using a Coulomb potential screened by a static dielectric constant. We compare our results with those of some recent calculations.1117479Strite, S., Morkoç, H., (1992) J. Vac. Sci. Technol. B, 10, p. 1237Gunshor, R.L., Kukimoto, H., Ruth, R.P., Special issue on wide-bandgap II-VI semiconductor materials (1993) J. Electron. Mater., 22, pp. 429-545Goldenberg, B., Zook, J.D., Ulmer, R.J., (1993) Appl. Phys. Lett., 62, p. 381Nakamura, S., Senoh, M., Mukai, T., (1993) Appl. Phys. Lett., 62, p. 2390Haase, M.A., Qui, J., Depuydt, J.M., Cheng, H., (1991) Appl. Phys. Lett., 59, p. 1272Khan, M.A., Kunzia, J.N., Olson, D.T., Blasingame, M., Bhattarai, A.R., (1993) Appl. Phys. Lett., 63, p. 2445Khan, M.A., Bhattarai, A., Kuznia, J.N., Olson, D.T., (1993) Appl. Phys. Lett., 63, p. 1214Ercelbi, A., Ozdinger, U., (1986) Solid State Commun., 57, p. 441Degani, M.H., Hipolito, H., (1987) Phys. Rev. B, 35, p. 4507Matsuura, M., (1988) Phys. Rev. B, 37, p. 6977Fröhlich, H., (1954) Adv. Phys., 3, p. 325Mori, N., Ando, T., (1989) Phys. Rev. B, 40, p. 6175Xie, X.J., Chen, C.Y., (1994) J. Phys.: Condens. Matter, 6, p. 1007Haken, H., (1956) Nuovo Cim., 10, p. 1230Lee, T.D., Low, F., Pines, D., (1953) Phys. Rev., 90, p. 297Aldrich, C., Bajaj, K.K., (1977) Solid State Commun., 22, p. 157Haga, E., (1955) Prog. Theor. Phys. Kyoto, 13, p. 555Pollman, J., Büttner, H., (1975) Solid State Commun., 17, p. 1171(1977) Phys. Rev. B, 16, p. 4480Sanders, G.D., Bajaj, K.K., (1987) Phys. Rev. B, 36, p. 4849Lawaetz, P., (1971) Phys. Rev. B, 4, p. 3460Nakayama, T., (1990) J. Phys. Soc. Japan, 59, p. 1029Andreani, L.C., Pasquarello, A., (1990) Phys. Rev. B, 42, p. 8928Cingolani, R., Lomascolo, M., Lovergine, N., Dabbicco, M., Ferrara, M., Suemune, I., (1994) Appl. Phys. Lett., 64, p. 243

Combined optical, structural and theoretical assessment of MOCVD grown multiple GaAs quantum wells

Materials Research Society Symposium Proceedings326359-364MRSP

Nitrogen incorporation and optical studies of GaAsSbN/GaAs single quantum well heterostructures

In this work, the effects of N incorporation on the optical properties of GaAsSbNGaAs single quantum wells (SQWs) have been investigated using temperature, excitation, and magnetic dependencies of photoluminescence (PL) characteristics. These layers were grown in an elemental solid source molecular beam epitaxy system with a rf plasma N source. The N concentrations in the range of 0.5%-2.5% were investigated in this study. The SQW with N∼0.5% exhibits a behavior similar to that in an intermediate regime where the contributions from the localized states in the band gap are dominant. The temperature and excitation dependencies of the PL characteristics indicate that for the N concentration of 0.9% and above, the alloy behavior is analogous to that of a regular alloy and the changes in optical properties are only marginal. The conduction band effective mass (meff) values computed from the magnetophotoluminescence spectra using a variational formalism and the band anticrossing model are in good agreement and indicate enhanced values of meff. However, there is no significant variation in meff values of QWs for N0.9%. Small redshift of about 30-50 meV for the temperature variations from 10 to 300 K in conjunction with unusually small blueshift observed in the excitation dependence of PL for N0.9% indicate that this system holds a great promise for laser applications at 1.55 μm and beyond. © 2007 American Institute of Physics