Influence of preparation procedure on the characteristics of Schottky barriers fabricated in situ on MBE GaSb

Schottky barriers have been prepared on molecular beam epitaxy (MBE)-grown n-type GaSb by depositing Al in situ. In order to prevent both Sb evaporation at high temperatures and Sb condensation during cooling of the epilayers before the metal deposition, the Sb shutter has been closed at a properly chosen temperature. It is shown that the time, Ar, spent at this temperature with the Sb shutter closed strongly affects both the I-V and C-V characteristics of the barriers. The barrier height values determined by I-V measurements are unreliable due to the non-ideal features of the diodes and to hole injection which is pointed out by deep level transient spectroscopy (DLTS) measurements. Conventional C-V measurements give surprisingly large values of the diffusion potentials and of the donor concentration. These values can be corrected by combining a modified dual-frequency technique with an excess capacitance correction. It is shown that, consistent with the I-V investigation, increased Δt values result in a significant worsening of the barrier quality.