Optical properties of tellurium-doped InxGa1-xAsySb1-y epitaxial layers studied by photoluminescence spectroscopy (original) (raw)
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physica status solidi (c), 2004
ABSTRACT The influence of tellurium doping on the optical properties of InxGa1–xAsySb1–y epitaxial layers has been studied by photoluminescence (PL) spectroscopy. PL was carried out by exciting the sample with the 488-nm line of an Ar-ion laser, changing the exciting power in the range between 40–200 mW and varying the temperature in the range 15–300 K. For the low-doped sample the PL spectrum showed a narrow exciton-related peak at 648.6 meV with a full width at half maximum (FWHM) of about 7 meV, which is an evidence of the good crystalline quality of the layers. For higher Te doping, the PL spectra showed the presence of band-to-band and donor-to-acceptor transitions which overlap as the Te concentration increases. The peak of the PL band shifts to higher energies as Te doping increases due to a band-filling effect as the Fermi level enters into the conduction band. The temperature dependence of the PL spectra for those samples with higher Te doping show a broad band at intermediate energies which disappear for temperatures above 80 K which is a typical behavior for a transition associated to DX deep defects. (© 2004 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)
Spectral distribution of excitation-dependent recombination rate in an In0. 13Ga0. 87N epilayer
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Physical Review B, 2004
We studied the shape and energy position of near-band-edge photoluminescence spectra of InN epitaxial layers with different doping levels. We found that the experimental spectra of InN layers with moderate doping level can be nicely interpreted in the frames of the ''free-to-bound'' recombination model in degenerate semiconductors. For carrier concentrations above nϾ5ϫ10 18 cm Ϫ3 the emission spectra can also be modeled satisfactorily, but a contribution due to a pushing up of nonequilibrium holes over the thermal delocalization level in the valence band tails should be considered in the model. The emission spectra of samples with low doping level were instead explained as a recombination from the bottom of the conduction band to a shallow acceptor assuming the same value of the acceptor binding energy estimated from the spectra of highly doped samples. Analyzing the shape and energy position of the free-electron recombination spectra we determined the carrier concentrations responsible for the emissions and found that the fundamental band gap energy of InN is E g ϭ692Ϯ2 meV for an effective mass at the conduction-band minimum m n0 ϭ0.042m 0 .
Far-infrared (FIR) magnetotransmission has been investigated in molecular-beam-epitaxy-grown Pbl "Eu"Tefilms with Eu concentration x =0.02. The experiments were carried out at fixed FIR photon energies between 2.5 and 21.4 meV, in the temperature range 1.8~T~60 K, and in magnetic fields up to 6 T. From the magnetic-field dependence of the cyclotron-resonance energies the momentum matrix elements have been determined within the framework of the Mitchell-Wallis k. p mode1: 2P /m0=8. 23+0.02 eV and 2PI /m0=0. 55+0.02 eV. The results signal a strong increase of band anisotropy due to the presence of Eu, from P, /PI'=10. 3 for pure PbTe to P, /PI = 14.9 for Pbp 98Euo p2Te. The low-field approximation of the model yields the following components of the effective-mass tensors: m, "/ma=0. 023, m~"/ma=0. 287, m, '/m0=0. 020, and m&'/ma=0. 218. A resonant transition from shallow acceptor states to valence band has also been observed. The analysis of these transitions in finite magnetic fields provided the value of the valence-band g factor, g, "= 15.9. This in turn served to place an upper limit on the valence-band exchange integral a, a =-7.5+5.5 meV. The small value of a indicates that the hole-Eu exchange interaction in the Pbl "Eu"Te system is at least one order of magnitude weaker than the hole-Mn interaction in Pb& "Mn"Te, and two orders of magnitude below exchange parameters in II l "Mn"VI systems. I. INTRODUCTION Lead salt alloys have been of great importance as materials for infrared diode lasers commonly used in molecular spectroscopy, in heterodyne detection, and in trace gas analysis. Because of the rapid increase of their energy gaps with Eu + content Pb& Eu Te and Pb, "Eu"Se alloys constitute attractive candidates for laser materials in the mid-infrared energy region. Both of these alloys, and their quaternary relative Pb& "Eu"Te& Se, are also used for energy barriers in multi-quantum-well Pb
Photoluminescence of n‐InN with low electron concentrations
… status solidi (a), 2006
Photoluminescence (PL) of n-InN grown by molecular beam epitaxy with Hall concentrations from 3.6 × 10 17 to 1.0 × 10 18 cm-3 demonstrates new features as compared with that of the samples of previous generation which are characterized by a higher carrier concentration. The striking dependences of PL spectra on carrier concentration, temperature, and excitation density give evidences of a fast energy relaxation rate of photoholes and their equilibrium distribution over localized states. The well resolved structure consisting of three peaks was observed in the PL spectra of these samples in the energy interval from 0.50 to 0.67 eV at liquid helium and nitrogen temperatures. We attributed one of two low-energy features of the spectra to the recombination of degenerate electrons with the holes trapped by deep acceptors with a binding energy of E da = 0.050-0.055 eV and the other one is attributable to the LO-phonon replica of this band. The higher-energy PL peak is considered as a complex band formed by two mechanisms. The first one is related to the transitions of electrons to the states of shallow acceptors with a binding energy of E sh = 0.005-0.010 eV and/or to the states of Urbach tail populated by photoholes. The second mechanism contributing to this band is the band-to-band recombination of free holes and electrons. Relative intensities of two higher-energy PL peaks were found to be strongly dependent on temperature and excitation power. At room temperature, the band-to-band recombination of free holes and electrons dominates in PL. Experimental results on PL and absorption are described by the model calculations under the assumptions of the band gap equal to 0.665-0.670 eV at zero temperature and zero carrier concentration and the non-parabolic conduction band with the effective mass at Γ-point equal to 0.07 of free electron mass.
Ge Related Deep Level Luminescence in InGaAs Lattice Matched to InP
MRS Proceedings, 1989
Photoluminescence and Hall measurements are reported on Ge doped InGaAs layers lattice matched to InP. Ge doping of these samples results in highly compensated material, with the highest Ge content sample giving a p type conductivity with carrier concentration of 5 ×1017 cm-3. Low temperature PL spectra of these samples show a broad peak from 0.55 to 0.77 eV due to Ge. The peak of luminescence shifts to lower energy with increasing Ge content. The peak position shifts to higher energy with increasing excitation like in a D-A pair transition. The PL spectra have been explained on the basis of a model which assumes tail states near the band edges due to disorder produced by the presence of Ge in the lattice.
Ge Related Defect-Complex Induced Luminescence in InGaAsP
MRS Proceedings, 1987
ABSTRACTGermanium doping of InGaAsP epitaxial layers grown by liquid phase epitaxy produces n type conduction with a net distribution coefficient KGe∼ 5×10-3. In addition, Ge doping introduces a broad band (∼0.2eV) of efficient luminescence which is red shifted with respect to the band edge. The intensity of this band grows with increasing Ge concentration. In all the samples, the integrated intensity of the broad band varies relatively less in the temperature range 15K to about 90K. At higher temperatures, the intensity falls exponentially with an activation energy of 0.05 - 0.07 eV. The emission spectra are compared with the configuration-coordinate model of the emission from a Ge related complex.