Determination of the electron concentration and mobility in the vicinity of a quantum well and $\delta$-doped layer in InGaAs/GaAs heterostructures

Comparative admittance measurements in mesadiodes on an $n^+$-GaAs substrate and in ring planar diode structures on an $i$-GaAs substrate, which contain a Si $\delta$-doped layer and an InGaAs quantum well in the GaAs epitaxial layer are performed. The possibility of determining the concentration profile and electron mobility in the vicinity of the $\delta$-doped layer and the InGaAs quantum well is shown based on an analysis of the simultaneously measured capacitance-voltage and conductance-voltage characteristics of the mesadiodes. By performing such measurements for $i$-GaAs-based ring diode structures with the given geometry, it is possible to reliably determine only the concentration profile. The influence of the relative location of the quantum well and $\delta$-doped layer on the concentration profile and mobility is revealed. The phenomenon of Maxwell relaxation in $i$-GaAs-based ring diode structures is discussed.