Selective-area epitaxy of carbon-doped (Al)GaAs by chemical beam epitaxy

Selective-area epitaxy (SAE) of carbon-doped (Al)GaAs by chemical beam epitaxy (CBE) using tris-dimethylaminoarsenic is investigated. Orientation of the growth front can significantly affect the growth rate of the regrown layers, resulting in facet formation around the mask. Moreover, the facets can be varied by adjusting the V/III ratio. For stripes along the [011̄] direction, the growth rate of (110) and (111)A planes is lowest when the V/III ratio is close to 1, resulting in lateral growth. This lateral growth has been exploited to fabricate heterojunction bipolar transistors (HBTs) with selectively regrown GaAs/AlGaAs:C external base layers. These HBTs exhibit a 62% reduction in the base sheet resistance and a higher current gain, compared to the original HBT structure. No degradation of the current gain is found after regrowth, demonstrating the great potential of SAE by CBE.