High-energy (400 keV) implantation of carbon (C) ions was made into LEC-GaAs substrates with C concentration ([C]) of 1019− 1022Cm−3. 2 K photoluminescence (PL) and Hall effect measurements indicated that activation rate of C in LEC GaAs is both optically and electrically extremely low even after furnace-annealing at 850 °C for 20 min. For [C] = 1×1022 cm−3, two novel strong emissions were obtained and PL measurements as a function of excitation power and sample temperature suggested that the two emissions one at 1.485 eV and the other at 1.305 eV should reflect the formation of a new alloy between GaAs and C. Dual implantation of C+ and Ga+ ions was carried out to improve the activation or substitution rate. We found that nearly 90% activation rate can be achieved for C dose of 2.2 × 1013 cm−2.

The criteria for forming stable cavities by He implantation and annealing are examined for Si and GaAs. In Si, implanting at room temperature requires a minimum of 1.6 at.% He to form a uniformly dense layer of cavities after annealing at 700°C. Near this threshold, cavities are located at dislocations and planar defects. Peak He concentrations just above 1.6 at.% produce narrow layers of cavities at the projected range. In GaAs, room-temperature implantation followed by annealing results in exfoliation of the surface layer. Cavities were formed instead by implanting Ar followed by overlapping He, both at 400°C, with additional annealing at 400°C to outgas the He. This method forms 1.5-3.5 nm cavities that are often on {111} planar defects.

Low energy neutral Ar ion-beam etching of n-GaAs was investigated as a possible “cleaning” procedure prior to contact metallization. The ion-beam source energy was varied between 35 eV and 1200 eV at a fixed current density of 1 mA/cm2. The effects of ion-milling on lightly doped n-GaAs were analyzed electrically by measuring current-voltage (IV) and capacitance-voltage (CV) characteristics of Schottky barriers formed after the ion-milling. The metal semiconductor barriers were prepared immediately following ion-milling without breaking vacuum. Photoluminescence and Rutherford Backscattering (RBS) were used to determine if any physical modification of the surface and near surface region of the ion-milled substrates had occurred.

Significant progress has been made in the past year in the use of high energy (MeV) ion irradiation to tune the bandgap and therefore emission wavelengths of single and multiple quantum well structures. These shifts are attributable to compositional mixing across the well and barrier layer interfaces, a process that is driven by the vacancy flux, released during the anneal stage, from radiation defects. We present data from a series of measurements in both GaAs- and InP-based QW structures to demonstrate the importance of the implantation parameters chosen (ion species, energy, flux, fluence and implant temperature). The dramatic difference in the response of these two systems with regard to the implant depth is believed to be associated with the very different diffusivities of the Gp III site vacancies. Prospects for implementing the irradiation approach as a spatially selective, planar process in integrated optoelectronic circuitry look very attractive and are illustrated for both passive and active components by reference to recent results from tuned wavelength lasers.

A comparison of ion irradiation-induced intermixing in GaAs-Al0.54Gao46As quantum well structures with H, O and As ions is investigated by low temperature photoluminescence. Very large energy shifts are observed together with good recovery of the photoluminescence intensities after annealing in samples irradiated with protons. No saturation in the energy shifts is observed in samples irradiated even up to a dose of 4.3 x 1016 cm-2. Similar large shifts with low absorption are also observed in O and As implanted samples but at a significantly lower ion dose. However, both the heavier ions show a saturation effect in the degree of intermixng at higher doses. The degree of intermixing is believed to be a delicate balance among multiple competing processes that occurs across the interface.

High energy (2 MeV) ion implantation of Fe in InP has been investigated by means of Rutherford backscattering spectrometry (RBS), transmission electron microscopy (TEM) and secondary ions mass spectrometry (SIMS). The implanted doses ranged between 5×l013 and 5×l014 at/cm2. Annealing in the 650–800 °C range was performed and the primary as well as secondary damage evolution has been studied. The correlations between defect structure and Fe redistribution properties have been carefully analysed. The results show the role of the primary defect structure in determining the annealing properties, both for damage recovery and Fe redistribution. The latter is also influenced by the doping of the substrate.

Hg (mercury) in GaAs is known to be a moderately deep acceptor impurity, having a 52 meV activation energy. Optical properties of Hg acceptors in GaAs were systematically investigated as a function of Hg concentration, [Hg]. Samples were prepared by high-energy ion-implantation of Hg+ into GaAs grown by the liquid encapsulated Czochralski (LEC) method. Heat treatment was made by furnace annealing and rapid thermal annealing. Photoluminescence measurements at 2K revealed that the Hg-related so-called “g” line is formed in addition to the well-defined conduction band-to-Hg acceptor transition, (e, Hg). Additionally, three shallow emissions are formed for net hole concentrations INA-NDI greater than 2×1017cm−3 . This is the first demonstration that even Hg in GaAs makes multiple shallow emissions due to acceptor-acceptor pairs and LEC GaAs can be used for the investigations of these emissions.

Furnace annealing (FA) and rapid thermal annealing (RTA) were made for Cd+ ion-implanted GaAs with Cd concentration, [Cd] from 1×1016cm−3 to 3×1021 cm−3. In FA samples, Raman scattering spectra exhibited a single peak at 292 cm−1 for entire [Cd] range which is LO-phonon mode from (100) GaAs. In RTA samples, LO-phonon mode is a single peak for [Cd]<1×1019cm−3 but with growing [Cd], TO-phonon mode appears for [Cd] 1×1020cm3 and becomes a dominant signal for [Cd]=3×1021 cm−3. The quenching of LO-phonon mode with increasing [Cd] was more clearly observed in RTA samples than in FA ones. Hall-effects results, however, showed that activation rate of RTA samples is 6–7 times larger than that of FA ones for [Cd] 1×1021 cm−3. 2K photoluminescence spectra revealed that in FA samples multiple shallow emissions associated with Cd are formed while in RTA ones the dominant emission is the band to Cd acceptor transition.

We have examined the role of co-implanted carbon in suppressing the formation of secondary defects in self-ion irradiated Si(100). Implantation of 540 keV energy Si ions to a fluence of 1015 cm-2 followed by a 900°C, 15 minute anneal leads to the growth of an extended defect band at the end-of-range. Range matched carbon co-implantation can be used to modify this defect development dramatically. While direct co-implantation of carbon and silicon ions has no apparent effect on the formation of extended defects, such formation can be suppressed when the implanted C is incorporated substitutionally into the silicon lattice. Ion channelling and nuclear reaction analysis show that substitutional carbon is removed from substitutional sites during Si ion irradiation. In this case, it is proposed that excess interstitial silicon ions which normally lead to the growth of secondary defects will occupy the lattice sites previously occupied by carbon ions.

A novel process for the fabrication of complex membrane structures in n-GaAs has been developed which utilises high energy nitrogen implantation and annealing to produce a semi-insulating etch stop layer and pulsed anodic etching for the selective removal of material. The process is versatile and can be used to produce complex, single crystal, stress-free, self-supporting membrane structures which are suitable for use as transducers operating up to ∼300°C. The semi-insulating properties of the membrane demonstrates its potential use as a substrate for electronic circuits.

The trend toward smaller dimensions in integrated circuit technology presents severe physical and engineering challenges for ion implantation. These challenges, together with the need for physically-based models at exceedingly small dimensions, are leading to a new level of understanding of fundamental defect science in silicon. Recently the DOE Council on Materials requested that our panel examine the current status and future research opportunities in the area of ion beams in semiconductor processing. Particularly interesting are the emerging approaches to defect and dopant distribution modeling, transient enhanced diffusion, high energy implantation and defect accumulation, and metal impurity gettering. These topics were explored both from the perspective of the emerging science issues and the technology challenges.

The results of alloying Al, Fe, and Mo surfaces by Be, Al, Ni, Sn under polyenergetic Ar+ ion beam irradiation with a mean energy of 10 keV have been presented. It has been shown that along with film and substrate materials sputtering there takes place the penetration of film atoms into substrate materials at a depth which is significantly greater (by a factor of 3… 10) than the projective range of ions in the given materials. The analysis of possible alloying depths with regard to different models (pure radiation range for monoenergetic ion beams; when the decrease of concentration is approximated by the exponential dependence; when the internal forcing out stresses are taken into account) for equal irradiation dose shows that the model, in which the migration of implanted atoms in the fields of forcing out stresses are considered, gives most close agreement between the calculated data and experimental ones.

Well-defined, homogenous, deep-buried 3C-SiC layers have been formed in silicon by ion beam synthesis using MeV C+ ions. Layers are characterized by RBS/channeling, X-ray diffraction, x-sectional TEM and electron diffraction. The redistribution of implanted carbon atoms into a rectangular carbon depth distribution associated with a well-defined layer during the post-implantation anneal is shown to depend strongly on the existence of crystalline carbide precipitates in the as-implanted state.

Nanocrystalline granular films of compositions Ag75Fe25, Ag61iFe39 are deposited on Si (001) substrates by ion beam deposition technique. The structure of as deposited and annealed (400°C/0.3 h) films is investigated by X-ray diffraction and the lattice parameter of the Ag particles is determined. The size of the Ag-particles is estimated from the line broadening of Ag(111) reflection and Scherrer formula and the values are 9 and 16 nm before and after the heat treatment. The magnetic moment and the saturation magnetization of the Fe-particles are determined from the magnetic field dependent magnetization data and using the Langevin function. A relationship between the structure and magnetism is discussed.