Shallow-donor impurities in indium selenide investigated by means of far-infrared spectroscopy

J. Martinez-Pastor, A. Segura, C. Julien, and A. Chevy
Phys. Rev. B 46, 4607 – Published 15 August 1992
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Abstract

Shallow impurities in n-type indium selenide (InSe) have been investigated by means of Fourier-transform spectroscopy in the far-infrared region. Three electric dipole transitions have been identified: 1s-2p±, 1s-2p0, and 1s-3p±, corresponding to electrons bound to native donors and tin-, silicon-, and chlorine-related donors, whose ionization energies (17.6, 18.1, 18.8, and 19 meV, respectively) have been determined through the Guerlach-Pollmann model. That model was also used to calculate the oscillator strengths of those dipole transitions, and then to estimate the shallow-donor concentrations in each sample. Native donors turn out to be the most hydrogenic ones, and the energies of their related transitions are used to determine a more accurate value of the low-frequency dielectric-constant product. An absorption line is observed in the low-energy side of the spectra (80 cm1) for samples with a donor concentration higher than 1015 cm3, which is attributed to impurity pairing. A mechanism is proposed to explain the large value of the full width at half maximum associated with the 1s-2p± absorption line (≊6.6 cm1 in the purest samples): Longitudinal-acoustic phonons polarized parallel to the c axis create dielectric-constant waves that modulate the dipole transition energies of shallow donors. In highly doped samples, compensating acceptors give rise to internal electric fields that largely broaden the absorption lines.

  • Received 16 March 1992

DOI:https://doi.org/10.1103/PhysRevB.46.4607

©1992 American Physical Society

Authors & Affiliations

J. Martinez-Pastor and A. Segura

  • Departamento Física Aplicada, Universitat de València, 46100 Burjassot, Valencia, Spain

C. Julien

  • Laboratoire de Physique des Solides, Université Pierre et Marie Curie, 4 place Jussieu, 75252 Paris, CEDEX 05, France

A. Chevy

  • Laboratoire de Physique des Milieux Condensés, Universitè Pierre et Marie Curie, 4 place Jussieu, 75252 Paris, CEDEX 05, France

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Vol. 46, Iss. 8 — 15 August 1992

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