Rapid heteroepitaxial growth of Ge films on (100) GaAs by pulsed supersonic free-jet chemical beam epitaxy

Very high epitaxial growth rates (0.25 μm/s), not attainable by conventional vapor phase film growth methods, have been obtained using a pulsed supersonic free jet to supply digermane (Ge₂H₆) for thermal decomposition at a heated (100)GaAs surface. Double-crystal x-ray diffractometry and scanning electron microscopy show that highly planar, smooth, and commensurate epitaxial Ge films are grown on (100)GaAs using gas pulses of 250 ms duration at 1-3 atm (0.1-0.3 MPa) pressure for substrate temperatures of 480-680°C. It is believed that the very high growth rates effectively "freeze" the Ge-GaAs interface resulting in minimal interfacial diffusion and reduced incorporation of impurities from the surrounding growth environment.