Noncontact doping level determination in GaAs using photoreflectance spectroscopy

摘要

Shifts of the band edge in GaAs layers as measured by photoreflectance (PR) spectroscopy have been accurately calibrated to theNhyphen;type doping level (Nd). Samples produced by controlled Sihyphen;doping experiments using ion implantation of GaAs substrates and GaAs doped with Si to known levels during growth by molecularhyphen;beam expitaxy have been investigated with this technique. A measurable change in the location of the band gap (E) determined from PR directly correlates with the maximumNhyphen;type doping level as determined viaChyphen;Vfor both types of samples with a change of band gap dgr;E/dgr;Nd=5.8plusmn;0.5times;10minus;20eVthinsp;cm3for 1times;1016cmminus;3le;Ndle;8times;1017cmminus;3. Correlations were also made to sheet carrier concentration (Hall measurements). This method is shown to be fast, accurate, and easily applicable to uniformity studies and a viable alternative to eitherChyphen;Vor Hall measurements for nondestructive determination ofNd.