No abstract

Using the strained-induced 2D–3D transition, InAs dots have been grown on InP(001) and examined by transmission electron microscopy. Two different modes of island size and spatial distribution have been identified. For deposit of 1.5 and 1.8 monolayers, the islands are about 7 nm high and randomly distributed. Above 2 monolayers, they are about five times smaller in volume and locally self-organized, with a typical distance of 40 nm independent of the island density. It is suggested that the strong dependence of the island size on the total amount of deposited InAs is mainly due to long range interactions through the substrate.

Unintentionally doped (100) InP wafers were ‘‘cleaned’’ with 12 different etching procedures, either found in the current literature or adapted from Si technology. We present the results of x-ray photoelectron spectroscopy (XPS) and Rutherford backscattering experiments together with electrical properties of Au/InP contacts realized on the same samples. We can distinguish: first, the solutions which result in a rather clean InP surface and give metal-semiconductor Au/InP diodes from those which lead to an approximately 20-Å-thick oxide layer and give metal-insulating-semiconductor structures, and second, the solutions which give electrically stable structures from those which lead to very unstable ones. Detailed electrical measurements [J-V; J(V,T); C(V,T)] have been performed on two kind of stable surfaces: on ‘‘clean’’ etched ones and on one oxidized with NH4OH-H2O2-H2O (5:1:100) solution. For the first ones, a quasi-ideal metal-semiconductor diode is found. For the oxidized surfaces, current flow is controlled by pure tunneling through the oxide layer. A correlation between surface composition evaluated with XPS and surface electrical properties has been clearly established: the electrical properties of the relatively P-rich oxides are quite unstable while the others, In rich, remain stable over several months. The composition and the nature of the various oxides are discussed.

Luminescence spectra and SIMS measurements of Er-doped silicon are presented in this paper. Luminescence was found to be stronger in Czochralski-grown Si crystals, known to contain up to 1018 cm-3 of oxygen center. Direct role played by oxygen impurities in the optical activation of the 1.54 µm luminescence was demonstrated by implanting oxygen into Er implanted layers in silicon at concentrations comparable to those of Er. Possible mechanisms of enhancement of photoluminescence are discussed.

Anomalous elevations up to 6 μm of the ion-implanted GaSb surface were observed. This swelling phenomenon is related to the formation of a porous layer and is dependent on the mass, energy, and dose of the implanted ions. A strong amount of oxygen was measured in the porous layers but this oxygen is likely not responsible for the swelling. The behavior of implanted GaSb is very similar to that of InSb previously described.