Calibration of the infrared absorption due to silicon in gallium arsenide

Abstract

The absolute infrared calibration of the SiGa centre in GaAs has been determined using samples analysed by atomic absorption spectrometry. It is shown that an absorption strength of alpha Delta =1 cm-2 due to the band at 384 cm-1 wavenumbers corresponds to a SiGa concentration of 6.0+or-1.0*1016 cm-3. Using grating IR spectrophotometers the measurement of this band in highly doped samples is found to be underestimated when the transmission falls below about 10%. It is shown that this photometric error arises from the measurement of a strong sharp line with instruments of limited resolution. A residual two-phonon absorption feature in this spectral region is present in undoped GaAs and this restricts the lowest SiGa measurable concentration to 5*1015 cm-3 when dispersive instruments are used.