Rapid isothermal processing based on incoherent sources of light is emerging as a reduced thermal budget processing technique for the fabrication of next generation of semiconductor devices and circuits. In this letter, we show that integration of the rapid isothermal processing unit and the ultrahigh vacuum deposition system provides aninsiturapid isothermal processing capability for the solid phase epitaxial growth of SrF2and BaF2films on (100) and (111)InP. We also show that neither as‐deposited norexsituannealed films show solid phase epitaxial growth.