Development of Si-based lasers is considered as the key to the realisation of fully integrated Si photonic circuits. Monolithic growth of III-V lasers on Si substrates is one of the most promising solutions for developing a commercially viable Si-based laser. However, the performances of current devices are still hindered by defects, hence the optimisation of crystal quality of the laser structures is of paramount importance. This paper reports on growth optimisation of thin Ge buffer layers on Si as an alternative to thick GaAs buffer layers. This method reduces the overall thickness and lowers the threading dislocation density in III-V semiconductors integrated on silicon platform.