Two‐phonon infrared absorption in In_1−xGa_xP mixed crystals

Abstract

The transmission spectra of Inl-,Ga,P mixed crystals (0 5 x 5 1) are measured between 20 and 550 K in the spectral range from 400 to 800 cm-l in which the optical absorption is due to two-phonon summation processes. The spectra of the end-member crystals and that of the mixed crystals consist of two main band groups in which up to seventeen structures are observed and pursued over the entire composition range. As an effect of disorder a broadening of the structures and an increase of absorption in the structureless region of the spectra are observed. The structures in the spectra are assigned to particulart two-phonon combinations or overtones of the various phonon branches -exploiting existing neutron and Raman data of the end-member crystals as well as the measured temperature dependence of the infrared spectra of mixed crystals. The compositional dependence of the LO, LA, TO, TA phonons at the X and L point and the LO, TO phonons a t the I? point are derived. It turns out that all phonon modes assigned display one-mode behaviour.Die Transmissionsspektren des Mischkristallsystems In1 -,Ga,P (0 5 z 5 1) werden zwischen 20 und 550 K im Spektralbereich von 400 bis 800 cm-1 gemessen, in dem die optische Absorption durch Zwei-Phonon-Summenprozesse verursacht wird. Die Spektren bestehen aus zwei dominierenden Bandengruppen, in denen bis zu siebzehn Strukturen beobachtet und uber den gesamten Zusammensetzungsbereich verfolgt werden konnen. Als Effekt der Unordnung findet man eine Verbreiterung der Strukturen und ein Anwachsen der Absorption in dem strukturlosen Bereich des Spektrums. Die Strukturen in den Spektren werden -unter Verwendung bekannter Neutronen-und Raman-Daten der Endkomponenten sowie der gemessenen Temperaturabhkngigkeit der Infrarotspektren der Mischkristalle -bestimmten Kombinationen oder Obertanen zweier,Phononen der verschiedenen Schwingungszweige zugeordnet. Daraus wird die Abhiingigkeit der LO-, LA-, TO-, TA-Phononfrequenzen an den Punkten X und L und der LO-und TO-Phononfrequenzen am Punkt I' von der Zusammensetzung abgeleitet. Alle diese Phononmoden zeigen Ein-ModenVerhalten.

Zone Edge Phonons in Gallium Phosphide

“…The proposed assignment scheme is presented in IR [21] IR [12,13 (cm-l) Concerning the proposed set of zone edge phonon frequencies, the following comments are to be made. Energies of the TA, LA, and TO phonons a t X, and of the TA and LA phonons a t I, quoted in Table 1 are in agreement with the values deduced by Hoff and Irwin [3] and by Ulrici and Jahne [7]. I n placing the LO(X) phonon at a value lower by an amount of 20 and 16 cm-l than given in The LO(L) phonon is also placed here below that of Hoff and Irwin [3] and Ulrici and Jahne [7] by an amount of about 20 cm-1.…”

“…Energies of the TA, LA, and TO phonons a t X, and of the TA and LA phonons a t I, quoted in Table 1 are in agreement with the values deduced by Hoff and Irwin [3] and by Ulrici and Jahne [7]. I n placing the LO(X) phonon at a value lower by an amount of 20 and 16 cm-l than given in The LO(L) phonon is also placed here below that of Hoff and Irwin [3] and Ulrici and Jahne [7] by an amount of about 20 cm-1. The corresponding neutron data of Yarnell et al [ l ] and Borcherds et al [2] differ considerably from each other (by an amount of 25 c i~i -~) , the difference being bigger by a factor of two than the sum of the quoted errors of the corresponding neutron data.…”

“…[5], and the IR absorption spectra by Ulrici and Jahne [7] were all analysed in terms of X and L phonons only. Hoff and Irwin [3] used also W point phonons in interpreting their Raman spectra, using the theoretical predictions of the second-neighbour ionic model developed by Banerjee and Varshni [8].…”

“…and[7], respectively, we were guided by an assessment of the data referring to momentum conserving phonons [13 to 181, and by the results of inelastic neutron scattering experiments [I,21. The proposed value for the LO(X) phonon is also in agreement with the theoretical result obtained from a 14-parameter second-neighbour shell model fit to the neutron data by Yarnell et al [I], and also froin the overlap shell model fit to the neutron data by Borcherds et al [2].…”

Carrier relaxation dynamics in InP quantum dots studied by artificial control of nonradiative losses

“…21͒ and Ga 0.5 In 0.5 P . 22 The rising kinetics of the PL in these peaks are faster than in the rest of the acoustic part of the spectrum. This observation is evidence of efficient relaxation of electron-hole pairs with emission of high-frequency acoustic phonons, in stark contrast with theoretical predictions.…”