Identification of the major residual donor in unintentionally doped InP grown by molecular beam epitaxy

The properties of InP grown unintentionally doped by molecular beam epitaxy are generally limited by residual free-carrier concentrations (ND−NA)∼1016 cm−3. By combining two depth profiling techniques, secondary ion mass spectrometry and electrochemical capacitance-voltage measurements, the single donor impurity responsible for these high free-electron concentrations has been identified. Conclusive proof is presented which resolves the source of the impurity.