Heavily carbon doped ρ-type GaAs/In0.3Ga0.7 As strained-layer superlattices (SLSs) with hole concentrations as high as 1 × 1020 / cm3 were successfully grown for the first time by metalorganic molecular beam epitaxy (MOMBE) using trimethylgallium (TMG), solid arsenic and solid indium. The single quantum well (SQW) and multiple quantum well (MQW) structures with different well width from 2 to 16nm were also designed to analyse the strain relaxation. The experimental results show that the SLS structures made of heavily carbon doped ρ—type GaAs and InGaAs have both of high hole concentration and small effective bandgap, which are satisfied for the application in heterojunction bipolar transistors (HBTs) as base layer.