CAPPING AND DECAPPING OF INP AND INGAAS SURFACES

An investigation of techniques for the preparation and preservation of stoichiometric InGaAs and InP surfaces, and techniques for regenerating these surfaces in vacuum have been carried out using x-ray photoelectron spectroscopy for surface characterization. It was found that InGaAs stoichiometric surfaces grown by molecular-beam epitaxy (MBE) can be preserved from oxidation and contamination by condensation of a thin layer of arsenic in the MBE chamber. The stoichiometric surfaces can be regenerated by thermal desorption of the arsenic cap in vacuum. Although stoichiometric InP surfaces can be prepared and arsenic capped in the MBE chamber, interfacial alloying between the arsenic cap and the substrate occurred during the thermal desorption process. Stoichiometric InGaAs and InP surfaces can also be preserved by a UV/ozone-formed oxide overlayer. For the removal of ozone-formed native oxides, thermal desorption at 458 °C regenerated clean and stoichiometric InP surfaces with a band bending of less than 0.3 eV on both n- and p-type substrates. However, complete oxide desorption on InGaAs required a temperature, above 565 °C, at which the surface decomposed. It was found that the ozone-formed surface oxides on InGaAs and InP could be removed at a substrate temperature below about 250 °C using a remote hydrogen plasma. The resultant n-InGaAs substrate surface was close to flat band, whereas the surface Fermi levels of the n- and p-type InP substrates were at 0.4 and 0.7 eV from the conduction-band minimum, respectively.