This paper reports on the investigation of GaInP/GaAs HBT-advanced structures with well-controlled strained base layers based on GaAs:C/GaInAs:uid superlattice heterostructures. High-resolution X-ray diffraction (HRXRD) and TEM experiments performed on test GaAs:C/GaInAs:uid superlattice heterostructures reveal well defined and sharp GaInAs/GaAs well/barrier interfaces with a high structural quality. C-V measurements and SIMS analysis, indicate that a low base sheet resistance is achieved with less carbon concentration than needed in the commonly HBTs C-doped GaAs base layers, together with a large strain reduction as shown by X-ray. HBT test structures consisting of 8-11 (GaAs:C/GaInAs:uid) period superlattice base layers, with GaInAs thickness varying from 0.5 to 3.4 nm have been processed. It is demonstrated that the GaInAs layer thickness must be less than 1 nm to preserve the current gain beta of the device.