Molecular beam epitaxy of low-resistance polycrystalline p-type GaSb

We report, for the first time, the growth and electrical properties of low resistance carbon-doped polycrystalline GaSb (poly-GaSb) by molecular beam epitaxy using CBr₄. The resistivity of poly-GaSb has strong dependence on film thickness and the grain size of the polycrystalline film, particularly when the film thickness is comparable with the grain size. It is found that grain size is determined by growth temperature, while hole concentration is significantly affected by antimony to gallium beam flux ratio. With same doping level, grain size, and similar film thickness, the resistivity of carbon-doped poly-GaSb is more than one order of magnitude lower than that of carbon-doped poly-GaAs. This is attributed to GaSb´s favorable surface Fermi-level pinning in the valence band and higher hole mobility. It is proposed that carbon-doped poly-GaSb be used as extrinsic base material in InP heterojunction bipolar transistor to improve the device´s high-frequency performance.