Contactless characterization of manganese and carbon delta-layers in gallium arsenide

Single manganese and carbon $\delta$-layers in undoped GaAs are analyzed by photoreflectance spectroscopy. The strength of built-in electric fields, determined by this method, is shown to increase with increasing layer concentration of introduced impurities and well correlate with technological and Hall data. The use of phase-sensitive photoreflectance makes it possible to measure the surface field and the field induced by $\delta$-doping separately. This fact allows one to determine without contact the fraction of electrically active Mn impurity and reveal the contribution of carbon $\delta$-layers to the characteristics of GaAs-based heterostructures.