Infrared Reflectance of the GaAlAs/GaAs System

Abstract

The simple additive form of the dielectric function is used to describe the IR reflectance of the GaAlAs/GaAs system. A detailed numerical study shows a different degree of importance of the parameters involved. A reasonable correspondence is found between the experimental and model spectra; the discrepancies are, most probably due to the aluminium concentration gradient in the GaAlAs layer. The values of some important parameters (aluminium content and the plasma frequency) may be determined directly from the characteristic features of the spectra without the elaborate fitting procedure provided the layer thickness is not too small.

OPTICAL PROPERTIES: BULK GaAs AND RELATED MATERIALS

“…x As (x=0-0.54) in the frequency range 240-700 cm ' 1 at close to normal incidence (i.e., within approximately a 10° angle of incidence). The crystals were undoped and had free-electron concentrations in low 5xl0 16 cm" 3 . The reflectivity data were analyzed by using the KK dispersion relations and by curve fitting to the two forms for the classical dielectric function, one the additive form of Eq.…”

“…x As layers have been studied by Lukes et al 16 using the two-grating and Fourier-transform spectroscopies. The AlAs content x in the layers varied from 0.05 to 0.77 and their thicknesses were in the range 4 to 38 urn.…”

“…Figure 11. 16 Fitted results of HOA model to the experimental e,(E) spectrum for GaAs. The experimental data are taken from Aspnes et al 22 Individual contributions to e, of the four harmonic oscillators are also shown by the light solid lines.…”

“…t As alloy (x=0.3-0.9) at temperatures 4 and 293 K. The samples were grown by liquid-phase epitaxy on GaAs substrates. They were nominally undoped and were n type with carrier concentrations at 300 K varying between 5xl0 16 and lxlO 17 cm" 3 . The samples were treated by removing the GaAs substrates with a selective chemical etching.…”

“…146 " 8 Braunstein and Kane 146147 have measured absorption spectra in p-GaAs between photon energies 0.05 and 0.8 eV for hole concentrations from 9.7xl0 16 6.8xl0 17 cm" 3 . The absorption spectra obtained by them are shown in Fig.…”