High hole mobility polycrystalline gasb thin films

In this paper, we report on the structural and electronic properties of polycrystalline gallium antimonide (poly-GaSb) films (50–250 nm) deposited on p⁺ Si/SiO₂ by metalorganic vapour phase epitaxy at 475^◦C. GaSb films grown on semi-insulating GaAs substrates are included as comparative samples. In all cases, the unintentionally doped GaSb is p-type, with a hole concentration in the range of 2 × 10¹⁶ to 2 × 10¹⁷ cm⁻³ . Exceptional hole mobilities are measured for polycrystalline GaSb on SiO₂ in the range of 9–66 cm²/Vs, exceeding the reported values for many other semiconductors grown at low temperatures. A mobility of 9.1 cm²/Vs is recorded for an amorphous GaSb layer in a poly-GaAs/amorphous GaSb heterostructure. Mechanisms limiting the mobility in the GaSb thin films are investigated. It is found that for the GaSb grown directly on GaAs, the mobility is phonon-limited, while the GaSb deposited directly on SiO₂ has a Coulomb scattering limited mobility, and the poly-GaAs/amorphous GaSb heterostructure on SiO₂ displays a mobility which is consistent with variable-range-hopping. GaSb films grown at low temperatures demonstrate a far greater potential for implementation in p-channel devices than for implementation in ICs.