The influence of phonons and impurities on the broadening of excitonic spectra in gallium arsenide

Abstract

The absorption spectra near the fundamental edge of gallium arsenide are measured in the temperature range of 4.2 to 500 K on samples with concentration of charged impurities from 1014 t o 1018 C I T -~. The description of the experiment by phenomenologically broadened theoretical spectra enables to determine the broadening parameter as a function of temperature and impurity concentration.

Composition and structure of HCl-isopropanol treated and vacuum annealed GaAs(100) surfaces

“…15 The proposed SBSRS method may be efficiently used for the measurements of temperature of the doped GaAs, because in this case the line shape of the optical absorption edge is determined by the band tails rather than by phonons. 15 The accuracy of the temperature measurements was found to be equal to Ϯ3°.…”

Optical properties of excitons in ZnO-based quantum well heterostructures

“…The important implication of this result is that the reduced excitonphonon coupling in QWs favors the exciton stability leading to a dominant excitonic role in the optical processes of ZnO QWs under strong injection or high temperatures. For comparison, Γ LO values for GaAs [42], ZnSe [43], CdTe [40,44] CdS [40] and GaN [45] It is found that the excitonic luminescence in the ZnO MQWs under investigation is attributed due to the radiative recombination from the excitons localized by the fluctuation with spatial well width fluctuation etc. The evidences of our spectral assignment are; (1) the well width dependence of Stokes shift (energy difference of absorption and lumines-cence bands), (2) the temperature dependence of PL spectra, and (3) the spectral distribution (luminescence energy dependence) of decay time constants of luminescence.…”

Analysis of the Low-Temperature (77 K) Near-Band-Edge Luminescence in Undoped Semi-Insulating GaAs

“…It was shown that this process can contribute to the broadening of the exciton spectra, but the predicted effect is too small compared with the one we observe (it is of minor importance in our crystals). In fact, at N % 3 Â 10 16 cm ± ±3 the found random field-induced increase in the halfwidth G ion is 0.4 meV [10] and the observed impurity-induced increase in the half-width G * ion G À w 1min is 2.9 meV (see Fig. 5).…”

“…4 ) Practically they do not take into account the possible interaction of a free exciton with an impurity during the radiative transition. Only in [10] the interaction of free excitons with the random field of charged impurities was investigated. It was shown that this process can contribute to the broadening of the exciton spectra, but the predicted effect is too small compared with the one we observe (it is of minor importance in our crystals).…”

“…In fact, the spectral shape of the free exciton absorption is given in[7,10]. The free exciton emission spectra can be deduced from the absorption coefficient using the so-called van Roosbroek-Shockley relation[5,8,9].…”