Design and operation of a valved solid-source As2 oven for molecular beam epitaxy

The design and operation of a valved solid-source of arsenic for molecular beam epitaxy is described. The addition of a throttle valve to a solid-charge arsenic source allows the arsenic flux to be varied rapidly and controllably during epitaxial growth with a time constant of <1 s. In addition to the novel valve, the arsenic source assembly includes a large reservoir, a thermal cracking zone for the production of As2, and provisions for adding an exit aperture ionization gauge for feedback flux control. Low-temperature photoluminescence from undoped GaAs grown with this source exhibited a neutral donor-bound exciton peak with full width at half-maximum of 0.128 meV, and lightly silicon-doped GaAs exhibited a mobility of 73 000 cm2/V s at 77 K, corresponding to ND =1.3×1015/cm3 and NA =2.0×1014/cm3.