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Scheme of recombination processes in n-doped GaAs at band-to-band photoexcitation leading to THz PL: (a) optical excitation of (e)–(h) pairs, (b) relaxation of nonequilibrium carriers and recombination of free holes with electrons of neutral donors, and (c) THz radiative transitions of nonequilibrium electrons contributing to binding to ionized donors.
Typical THz PL spectrum (solid curve) for undoped GaAs layer . . Excitation −645 nm line of semiconducting laser. . The dashed line is calculated emission spectrum for optical transitions of electrons with from the conduction band continuum to the donor ground state 1S. The arrow points to the energy of 4.4 meV corresponding to intracenter optical transitions for a shallow donor in GaAs (Ref. 2). The figure inset shows the spectra of near band edge PL of these samples excited by 645 nm line of semiconducting laser. , . Arrows point to the (recombination of exciton bound to neutral donor) and (free-to-bound recombination) emission lines, at 1.514 eV and 1.513 eV, respectively, identified in accordance with published data (see, for example, Ref. 8).
Temperature dependence of the spectrally integrated intensity of the THz PL from undoped GaAs layer. . Points are experimental data. The solid curve shows the least square fit of the experimental data by equation with and . The figure inset shows the dependence of the spectrally integrated THz PL intensity on the excitation density for undoped GaAs layer at 5 K. Points are experimental data. Curve is the result of approximation of the data by law.
Spectra of THz PL from Si-doped n-GaAs layer with (curve 1), undoped GaAs layer with (curve 2) and Si-GaAs substrate sample (curve 3). , .
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