The effect of thermal annealing on Te compensated Interfacial Misfit GaSb/GaAs heterostructures is investigated by using two different thermal annealing procedures, namely rapid thermal annealing and furnace annealing. The electrical properties of the devices are studied by using Current–Voltage, Capacitance–Voltage and Deep Level Transient Spectroscopy techniques. It is observed that rapid thermal annealing treatment is superior in terms of improvement of the electrical characteristics compared to furnace annealing treatment. The lowest leakage current and defect concentration are obtained when rapid thermal annealing is employed.