Defect and interface analyses of non-stoichiometric n-type GaSb thin films grown on Ge(100) substrates by rapid thermal annealing

Highlights: • The conductivity of Ga0.6Sb0.4/Ge(100) is n-type at RT but p-type at low temperature. • Ga0.6Sb0.4/Ge(100) contains two types of acceptors and two types of donors. • Electrically active sites at the Ga0.6Sb0.4/Ge interface act as donors and acceptors. - Abstract: In this study, Ga_0.6Sb_0.4 thin films were grown on quartz and Ge(100) 1° off-axis substrates by RF magnetron sputtering at 500 °C. Ga_0.6Sb_0.4/Ge(100) shows n-type conductivity at room temperature (RT) and p-type conductivity at low temperatures, whereas undoped GaSb thin films exhibit p-type conductivity, irrespective of their growth methods and conditions. Their electrical properties were determined by rapid thermal annealing, which revealed that Ga_0.6Sb_0.4/Ge(100) contains two types of acceptors and two types of donors. The acceptors are considered to be Ga_Sb and electrically active sites on dislocations originating at the Ga_0.6Sb_0.4/Ge(100) interface, while donors are believed to be Ga_i and electrically active sites originating at the Ga_0.6Sb_0.4/Ge(100) interface. In these acceptors and donors, the shallow donor concentration is higher than the shallow acceptor concentration, and the shallow donor level is deeper than the shallow acceptor level. Thus, we concluded that Ga_0.6Sb_0.4/Ge(100) shows n-type conductivity at RT due to electrically active sites originating at the Ga_0.6Sb_0.4/Ge(100) interface and native defects originating from excess Ga.