A. Verna

Phase separation and dilution in implanted MnxGe1-x alloys

The structural and electronic properties of MnxGe1−x alloys (x⩽0.15) fabricated by ion implantation are investigated by means of x-ray diffraction and synchrotron radiation photoemission spectroscopy. The diffraction patterns point to the presence of ferromagnetic Mn5Ge3 nanoparticles; however, valence band spectra, interpreted by means of accurate ab initio calculations including Hubbard-like correlations, show clear fingerprints of an effective substitutional Mn dilution in the Ge semiconducting host.

Mechanisms for the activation of ion-implanted Fe in InP

In this paper we present structural and electrical investigations on high temperature Fe-implanted InP. The aim of the work is to relate the lattice position of the implanted atoms after annealing treatments (from 300to600°C) with their electrical activation as compensating deep traps and to draw a comprehensive picture of the activation mechanisms. The overall results demonstrate that the electrical behavior and the Fe2+ deep trap activation properties are strictly connected to the annealing evolution of the implant-induced damage and to the escape process of the Fe atoms from substitutional sites, which in turn is controlled by the background doping density in the substrates.

Localization of the dopant in Ge:Mn diluted magnetic semiconductors by x-ray absorption at the Mn K edge.

A unitary picture of the structural properties of Mn(x)Ge(1-x) diluted alloys fabricated by either ion implantation or molecular beam epitaxy (MBE), at various growth temperatures (from 80 to about 623 K) and few per cent concentrations, is proposed. Analysis is based on synchrotron radiation x-ray absorption spectroscopy at the Mn K edge. When the growth temperature exceeds 330 K, the MBE samples show a high number of precipitated ferromagnetic nanoparticles, mainly Mn(5)Ge(3), nucleated from the previous occupation of interstitial tetrahedral sites. Efficient substitution is observed in the case of MBE samples made by alternate layers of GeMn alloys grown at T ≤ 433 K and undoped Ge thick layers. Similar good dilution properties are obtained by implanting Mn ions at low temperatures (80 K). Possible precursors to preferential mechanisms in the alloy formation are discussed on the basis of the present comparative study.

Electrical activation of the Fe2+/3+ trap in Fe-implanted InP

We have studied the electrical activation of the Fe2+∕3+ trap in Fe-implanted InP by means of capacitance-voltage and deep level transient spectroscopy analyses. Five deep traps have been identified and we have characterized the concentration and depth distribution of the Fe2+∕3+ deep trap, located at EC–0.66eV. The InP substrate background doping, i.e., the Fermi-level position, plays a crucial role in the Fe activation process by setting an upper limit to the amount of Fe centers electrically activated as deep acceptor traps.

Electrical Activation Of Fe Impurities Introduced In III‐V Semiconductors By High Temperature Ion Implantation

We performed structural and electrical investigations on high temperature Fe implanted InP in order to correlate the lattice position of the implanted atoms after annealing treatments to their electrical activation as compensating deep traps. The overall results demonstrate that the Fe2+ deep trap activation properties are strictly connected to the annealing evolution of the lattice location of the Fe atoms in substitutional sites, which in turn is controlled by the background doping density in the substrates.

Deep levels characterization in high temperature iron implanted InP

We have investigated the electrical activation of Fe implanted in InP in different concentrations and we have characterized by DLTS and by C-V analyses the electrical activity of the deep levels present in the band gap.

Structural and electrical investigation of high temperature Fe implanted GaInP layers lattice matched to GaAs

Single GaInP layers, grown by MOVPE lattice matched to GaAs are examined. The role of the implantation temperature and dose in determining the crystal damage, and the recovery of this damage by the following high temperature annealing treatments is investigated by RBS-channeling measurements. The influence of implant and annealing conditions on the redistribution properties of the Fe atoms throughout the crystal is studied by means of SIMS Fe depth profiling. High-resolution X-ray diffraction measurements are employed for structural characterization. The electrical properties related to Fe implantation are studied by current-voltage measurements on mesa devices. Deep level properties are investigated by DLTS-PICTS measurements.