Quantitative determination of the doping level distribution in n-type GaAs using absorption mapping

We present an optical technique based on absorption measurements for the determination of the charge carrier concentration and its lateral distribution in n-type doped GaAs wafers. Calibration plots were determined in the charge carrier concentration range of 3 × 1017 m−3... 1 × 1018 cm−3 (range of trust up to 3 × 1018 cm−3) which is technically relevant for applications of GaAs wafers as substrate for laser and light emitting diodes. The error of the optical technique is in the range of 10% ... 15% and is comparable to electrical Hall measurements. The sensitivity of the setup, i.e. smallest detectable variation of doping (and hence charge carrier) concentration, is less than 1% in an area of 5 × 5 mm2 and about 20% across the 3 inch area. Absorption mappings of the charge carrier and hence doping homogeneity are presented for n-type GaAs:Si and GaAs:Te