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

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Abstract
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.