In/Sb is integrated with Si by a process of high energy heavy ion beam mixing. The samples of In/Sb deposited on the Si substrate were irradiated using 100 MeV Au ions having fluences from 1 × 1012 to 6 × 1013 ions cm−2. Phase formation due to ion beam mixing was detected using high-resolution x-ray diffraction measurements. X-ray photoelectron spectroscopy measurements indicated that both In and Sb were embedded in the Si substrate with an irradiation dose of 3 × 1013 ions cm−2. Formation of InSb phase was observed in the irradiated sample, at a fluence of 1 × 1013 ions cm−2and higher, without any post-irradiation annealing.