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

¹ Institute for Materials Science 6, University of Erlangen, Martensstr.7, D-91058 Erlangen, Germany
² Crystal Growth Laboratory, Fraunhofer Institute of Integrated Systems and Device Technology (IISB), Schottkystr. 10, D-91058 Erlangen, Germany
³ Freiberger Compound Materials GmbH, Am Junger Löwe Schacht 5, D-09599 Freiberg, Germany

Corresponding author: peter.wellmann@ww.uni-erlangen.de

Received: 4 July 2003
Accepted: 31 December 2003
Published online: 15 July 2004

Abstract

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.