• D Pal

      Articles written in Bulletin of Materials Science

    • Study of photoluminescence and computation of configuration coordinate diagram of Cu related deep levels in InP

      D Pal N Bose

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      Photoluminescence has been studied in Cu diffusedn andp-InP. Inp-InP a Cu related photoluminescence (PL) band was observed at 1·216eV. The temperature dependence of line-width was studied and line-shape and line-width analysis carried out. The configuration coordinate diagram of the band was calculated which showed a small lattice relaxation of 0·079 Å.

      Inn-InP two PL bands at 1·20 and 1·01 eV were found at 10 K. The former was similar to the 1·216eV band inp-InP. The PL of the 1·01 eV band was also studied in detail and the corresponding configuration coordinate diagram derived.

    • Lattice mismatch and surface morphology studies of InxGa1−xAs epilayers grown on GaAs substrates

      R Pal M Singh R Murlidharan S K Agarwal D Pal D N Bose

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      InxGa1−xAs (0·06≤x≤0·35) epilayers were grown on GaAs substrates by atmospheric pressure metal organic chemical vapour deposition technique. Surface morphology and lattice mismatch in the InGaAs/GaAs films of different compositions were studied. Cross-hatched patterns were observed on the surface of the epilayers for bulk alloy composition up tox≈0·25. Forx>0·3, a rough textured surface morphology was observed.

    • Transmission electron microscopy and X-ray diffraction studies of quantum wells

      D V Sridhara Rao K Muraleedharan G K Dey S K Halder G Bhagavannarayan P Banerji D Pal D N Bose

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      A series of InxGa1−xAs (x=0·47) quantum wells with InP barrier layers have been grown on InP substrates by metalorganic vapour phase epitaxy (MOVPE) at 625°C. The nominal well widths were defined during growth at (i) 25 Å, 39 Å, 78 Å and 150 Å for one sample and (ii) 78 Å for all 4 wells in another sample. The InP barrier widths have been kept constant at 150 Å. These layers have been characterized by X-ray diffraction (XRD) which from simulation gave the nominally 78 Å well width as 84 Å and the nominally 150 Å barrier width as 150·5 Å. Transmission electron microscopy (TEM) and high resolution TEM (HRTEM) have been carried out on etched and ion-milled samples for direct measurement of well and barrier widths. The well widths found from TEM are 25 Å, 40 Å, 75 Å and 150 Å. TEM micrographs revealed that, while the InP barrier layer is of good quality and the growth is confirmed to be epitaxial, dipoles are detected at the interface and the quantum well has some small disordered regions. These thickness measurements are in good agreement with earlier photoluminescence (PL) and secondary ion mass spectrometry (SIMS) studies.

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