Thermal desorption of oxide layers from InSb(001) substrates was studied using reflection high energy electron diffraction (RHEED), x-ray photoelectron spectroscopy, Auger electron spectroscopy, and scanning electron spectroscopy. Surfaces of as-loaded substrates prepared using either of two common chemical etchants were composed of oxide layers containing In2O3 and Sb2O5. As the substrate temperature was raised, a multistage desorption process was observed. Most of the Sb2O5 was reduced during the first stage, leaving behind a thin oxide layer consisting predominantly of In2O3. In2O3 was desorbed during the second stage, as the substrate temperature was raised further in the presence of an Sb flux. Indium droplets condensed on the surface before a smooth morphology ensued. We suggest that the reduction of In2O3 produced In droplets which reacted with the supplied Sb flux to form InSb. Annealing produced smooth, stoichiometric surfaces that gave rise to well-defined, Sb-stabilized pseudo-(1×3) RHEED patterns. InSb films grown on such substrates exhibited good structural and electrical properties.

Articles you may be interested inStudy of structural properties of cubic InN films on GaAs(001) substrates by molecular beam epitaxy and migration enhanced epitaxy Improved electron mobility in InSb epilayers and quantum wells on off-axis Ge (001) substrates Growth of InSb epilayers and quantum wells on Ge(001) substrates by molecular beam epitaxy Room-temperature ferromagneticlike behavior in Mn-implanted and postannealed InAs layers deposited by molecular beam epitaxyThe molecular beam epitaxy of InSb/Si structures was accomplished using group IIa fluoride buffer layers. InSb growth was initiated by opening the In and Sb shutters simultaneously at substrate temperatures between 300°C and 400°C, producing In-terminated InSb͑111͒-A surfaces on CaF 2 /Si͑111͒ substrates. Reflection high-energy electron diffraction, electron channeling, and high resolution x-ray diffraction measurements indicated that the InSb layers were of good crystalline quality. Electron mobilities at room temperature were as high as 65 000 cm 2 /V s for an 8-m-thick InSb layer grown on CaF 2 /Si͑111͒. On CaF 2 /Si͑001͒ substrates, the InSb layers grew in the ͑111͒ orientation with two domains 90°apart. These InSb layers and ones grown on BaF 2 /CaF 2 /Si͑111͒ substrates exhibited inferior electrical and structural properties compared to structures grown on CaF 2 /Si͑111͒ substrates.

Detailed studies of the often-observed resonance feature near 3.4 eV in the reflectance difference spectrum of Si/SiO2 interfaces and Si surfaces show that the resonance is due to the intrinsic local-field effect, and that its energy position coincides with the E1 energy of bulk Si. Using the energy position of the resonance of the pseudomorphically grown Si/CaF2 interfaces as a reference point, the strain-induced resonance energy shift of the Si interface layer at several Si/SiO2 interfaces are obtained and the strain in these layers is determined. The results show that the interface layers are highly strained with an equivalent hydrostatic pressure of 0.79 GPa, but still maintain a high degree of order.

RHEED intensity oscillations observed during MBE growth of CaF 2 on Si(1 11) and PbSe on CaF 2 /Si(1 11) are presented. The effects of substrate temperature and initial nucleation procedure are investigated. Strong temporal oscillations of the specular beam intensity are found to be most readily observed at temperatures below 200'C for both CaF 2 and PbSe. Growth rates measured as a function of cell temperatures exhibit Arrhenius behavior with activation energies of 5.0 eV and 1.93 eV for CaF 2 and PbSe, respectively. The relatively high activation energy obtained for CaF 2 is consistent with the high melting point and sublimation energy of ionic fluorides.

The initial stages of MBE growth of PbSe on CaF2/Si(111) were studied by in situ XPS. The surface reaction between CaF2 and elemental Se is also studied as a comparison. Ca 2p, F 1s, Pb 4f and Se 3d peaks all shift to lower binding energies (1.2 – 1.6 eV) with increasing PbSe coverage. This indicates a strong interaction between the PbSe overlayer and the underlying CaF2 and the formation of Pb-F and Ca-Se interfacial bonds. No chemically graded reaction products are detected at the PbSe/CaF2 interface. A transition layer of about 6 ML is observed which can be partially accounted for by the open 3D structure of CaF2 where three layers of atoms are available for bonding with the deposited material. This structure allows interpenetration of the PbSe and CaF2 layers which necessarily leads to a thin transition layer. Based on our XPS results, we propose a model for the bonding arrangements at the PbSe/CaF2(111) interface.