Photoreflectance of GaAs structures with a Mn $\delta$-doped layer

The strength of the built-in electric field in gallium-arsenide structures with a $\delta$-doped layer has been determined by photomodulation optical spectroscopy (photoreflectance) for different manganese contents in these structures. The samples under study have been grown by combining metal-organic chemical vapor deposition and laser sputtering of Mn and GaAs targets at a low temperature ($T_g$ = 400$^\circ$C). An increase in the Mn content in the $\delta$-doped layer from zero to 0.35 monolayer leads to an increase in the built-in electric field (averaged over the surface region) from 14 to 25 kV/cm. The data obtained are in good agreement with the results of self-consistent solution of the Schrödinger and Poisson equations for the real (manganese) distribution profile.