Effect of noble gas plasmas on the growth of InP by gas-source molecular beam epitaxy

InP layers were grown by gas-source molecular beam epitaxy over the temperature range 300-500°C whilst subjected to either He- or Ar-plasmas generated by an electron cyclotron resonance source. The energy of the ion component of the plasmas was varied by applying a DC bias (-75 to +40 V) to the substrate. He-plasma bombardment at zero bias produces high resistivity InP (ρ up to ∼105 ω-cm) for growth in the temperature range ∼375-475°C. Variable energy positron annihilation studies indicate the presence of a high concentration (∼4×1018cm-3) of open-volume defects. Ar-plasma growths yield good quality InP at 465°C and photoluminescence studies show features associated with donor to acceptor (D-A) and conduction band to acceptor (e-A) transitions. Also, the ion component in the plasmas plays a dominant defect production role at biases more negative than −40 V The results are explained on the basis of the production of P-vacancies, P-antisite defects and P-interstitials.