In this article the effect of hot phonons on the drift velocity of holes in the high-field transport regime of a Si SiGe modulation doped heterostructure is presented. A theoretical model including the hot phonon production effect is implemented to compare the experimental results of hole drift velocity at high fields. At liquid helium temperature, our experimental results show that at an electric field of 1000 V/cm the hole drift velocity saturates at around vd= 7× 105 cm/s which is in good agreement with the theoretical calculations based on the above model. The reduction of hole drift velocity at high fields is due to increasing momentum .relaxation rate which is a result of the enhanced production of non-drifting longitudinal optical phonons
