Annealing Study of Al/GaSb Contact with the Use of Doppler Broadening Technique

Using a monoenergetic positron beam, annealing study of the Al/n-GaSb system was performed by monitoring the Doppler broadening of the annihilation radiation as a function of the positron implanting energy. The S-parameter against positron energy data was successfully fitted by a three-layer model (Al/interface/GaSb). The annealing out of the open volume defects in the polycrystalline Al layer was revealed by the decrease in the S-parameter and the increase in the effective diffusion length of the Al layer. For the as-deposited samples, a 5 nm interfacial region with S-parameter larger than those of the Al overlayer and the bulk was identified. After the 400ºC annealing, this interfacial region extends to over 40 nm and its S-parameter dramatically drops. This is possibly due to the new phase formation at the interface. Annealing behaviors of S$\text{}_{B}$ and L$\text{}_{+,B}$ of the GaSb bulk showed the annealing out of positron traps (possibly the V$\text{}_{Ga}$-related defect) at 250ºC. However, a further annealing at 400ºC induces the formation of positron traps, which are possibly of another kind of V$\text{}_{Ga}$-related defect and the positron shallow trap GaSb antisite.