Substitutional disorder effects on optical spectra of extremely heavily doped Si : P obtained by ion implantation and laser annealing

The optical reflectivity spectrum (2500–5000 Å) of extremely heavily phosphorus (P)-doped Si has been studied. The E₁ and E₂ peaks, which represent the completeness of the Si crystal, are slightly affected when doping concentrations are less than 10²¹ cm^-3 (2% Si : P). However,they appreciably degrade as the doping concentration increases from 10²¹ to 5×10²¹cm^-3 (10% Si : P). As the result of band calculations using a supercell configuration and pseudopotential method, we have been able to ascribe this behavior to the substitutional disorder effect.     

Formation of heavily doped n-type layers in GaAs by multiple ion implantation

Rare earth doping of CaF₂ produces material which gives strong thermoluminescence signals. In an attempt to separate the influence of impurity and intrinsic defects CaF₂ has been implanted with ions of Ce, Dy, Mn, Ca and F. Comparisons are made with chemically doped samples and the effect of thermal treatments have been made in all cases. The cerium and dysprosium ions influence both the shallow charge trapping levels, which determine the temperature of the glow peaks, and the recombination sites which control the photon spectra.

After implantation the strong TL signals show emission at wavelengths near 360 nm for Ce, 480 nm for Dy and for Mn.

Re-excitation of the trapping levels reveals selective emission for some defects, restructuring of less stable defects and major changes in defect concentrations with thermal treatment. The effects of the impurity and intrinsic defects on the spectra are discussed. One major observation is that addition of cerium to “pure” samples does not enhance the TL sensitivity, whereas Dy and Mn both show new glow peaks. In the case of Dy it is thought that the charge trap and the luminescent site are directly linked within one complex defect.     

Effects of ion implantation on yellow luminescence in unintentional doped n-type GaN

The effects of Si, O, C and N ion implantation with different implantation doses on yellow luminescence (YL) of GaN have been investigated. The as-grown GaN samples used in the work were of unintentional doped n-type, and the photoluminescence (PL) spectra of samples had strong YL. The experimental results showed that YL of ion implanted samples exhibited marked reductions compared to samples with no implantation, while the near band edge (NBE) emissions were reduced to a lesser extent. The deep-level centers associated with YL may be produced in GaN films by O and C ion implantation, and identities of these deep-level centers were analyzed. It was also found that the dose dependence of YL was analogous with the one of the intensity ratios of YL to the near band edge (NBE) emission (I _YL /I _NBE ) for ion implanted samples. The possible reason for this comparability has been proposed.      

Supersaturated Si-As alloy formation by ion implantation and pulsed electron beam annealing

Supersaturated surface alloys produced by very high dose (0.8–2.6×10¹⁷cm^–2) implantation of As-ions into silicon and subsequent pulsed electron-beam annealing have been investigated by means of the channeling technique. The maximum solubility limit of 7×10²¹ As/cm³ has been determined. It exceeds the equilibrium solubility limit by more than a factor of 4. Angular scan measurements indicated that for doses above 1×10¹⁷cm^–2 As atoms are displaced by about 0.12 Å from the regular lattice sites.     

Metal-insulator transition in amorphous Si1−c Mnc obtained by ion implantation

A metal-insulator transition (MIT) induced by a change in the impurity Mn concentration in a material with topological disorder — amorphous Si_1−c Mn_c — is investigated. It is found that near the critical point the localization radius, permittivity, and conductivity vary according to a power law in accordance with the scaling theory of localization. The critical exponents are determined. It is concluded that the basic mechanisms of the MIT in disordered systems do not depend on the type of disorder and are universal. Pis’ma Zh. éksp. Teor. Fiz. 65, No. 4, 333–337 (25 February 1997)     

Self-assembled SiGe quantum dots embedded in Ge matrix by Si ion implantation and subsequent annealing

We have fabricated SiGe quantum dots (QDs) by means of a two-step Si ion implantation followed by thermal rapid thermal annealing (RTA) method. SiGe QDs with the 4–6 nm diameter are formed uniformly in the near-surface region of Ge substrate. The RTA processes are performed at 800 and 900 °C for 15 s, respectively. Both experimental and theoretical analysis indicates that the higher temperature (900 °C) RTA can enhance the growth of SiGe QDs. Two photoluminescence peaks are observed near 572 and 581 nm at room temperature. The mechanism of the luminescence from SiGe QDs is discussed.     

Photoluminescence in heavily doped Si: B and Si: As

We report the results of low-temperature photoluminescence measurements on a series of heavily-doped Si: As and Si: B samples. New spectra are obtained for very high doping levels (10¹⁹ 2- 10²⁰ cm^-3), and the results for the more lightly doped samples are found to be in good agreement with previously published data. By comparing the luminescence of a Si: As sample before and after partial compensation with B, we verify that minority carriers can be localized even in “metallic” samples.     

Effects of ion clusters on the performance of a heavily doped erbium-doped fiber laser

A cluster model is proposed for study of the effects of the number of ions per cluster on the performance of a heavily erbium-doped fiber laser. The results indicate that both the threshold pump power and the unstable-operation region of the fiber laser increase with increasing numbers of ions per cluster.     

Magnetic field dependence of the specific heat of heavily doped n-type silicon

The low temperature specific heat of an n-type phosphorous doped silicon sample containing 5 × 10¹⁸ charge carriers/cm³ in zero magnetic field and in a magnetic field of 28.5 kGauss has been measured. Within the experimental accuracy of the experiments no magnetic contribution to the specific heat has been detected. This result is discussed in the light of recent E.S.R. experiments on the same impurity banded silicon sample.     

Preparing buried Si3N4 layers by high-intensity ion implantation and rapid thermal annealing

Translated from Zhurnal Prikladnoi Spektroskopii, Vol. 53, No. 4, pp. 628–632, October 1990.     

Modeling of the impurity distribution obtained by ion implantation

Models and a suite of programs (TRION, PIRSON, CHAPS, and DYCOD) that make it possible to calculate the impurity distribution for any implantation dose in a target with arbitrary composition are described. Test calculations for each program showed that the results are in good agreement with experimental data and with theoretical calculations performed by other authors. The suite of programs is intended for the development of the physical principals of ion-beam technologies.Translated from Izvstiya Vysshykh Uchebnykh Zavedenii, Fizika, No. 5, pp. 8–22, May, 1994.     

Metastable surface alloys produced by ion implantation,laser and electron beam treatment

Ion Implantation, Laser and Electron-beam Treatment (LET) of metals have been employed extensively to produce metastable surface alloys. Recent published work on implanted alloys is reviewed first. The dilute implanted alloys (solute concentration <10 at. %) are shown to lead to crystalline metastable solid solutions. At higher solute concentrations, an amorphous phase has been observed for several binary systems and recently for a ternary system. The physical mechanisms at play, are discussed in detail. A review of the surface alloys produced by LET of metals is then presented—with an emphasis on the mechanisms involved. In particular, general criteria governing formation of metastable solid solutions under LET are proposed and shown to have excellent agreement with available data on metals and Si.     

On the electron energy spectrum in heavily doped non-parabolic semiconductors

An attempt is made to present a simple theoretical analysis of the energy-wave vector dispersion relation of the conduction electrons in heavily doped non-parabolic semiconductors forming band tails. We observe that the complex energy spectrum in doped small-gap materials whose unperturbed conduction band is described by the three band model of Kane is due to the interaction of the impurity atoms in the tail with the spin-orbit splitting constant of the valence band (Δ), For band-gap (E_g)<Δ the imaginary part predominates which tails in to the conduction band. For the opposite inequality the real part comes in to play which tails in to the split-off band. In the absence of the band tailing effect, the imaginary part of the complex energy spectrum vanishes and the same is also true for doped two-band Kane-type and parabolic energy bands respectively. The present formulation helps us in investigating the Boltzmann transport equation dependent transport properties of degenerate semiconductors and are expected to agree better with experiments. The well-known results of unperturbed three and two band models of Kane together with wide-gap parabolic energy bands have been obtained as special cases of our generalized analysis under certain limiting conditions.     

Ferromagnetism in ZnO doped with Co by ion implantation

The importance of doping ZnO with magnetic ions is associated with the fact that this oxide is a good candidate for the formation of a magnetic-diluted semiconductor. Most of the studies reported in Co-doped ZnO were carried out in thin films, but the understanding of the modification of the magnetic behaviour due to doping demands the study of single-crystalline samples. In this work, ZnO single crystals were doped at room temperature with Co by ion implantation with fluences ranging between 2×10¹⁶ and 1×10¹⁷ ions cm⁻² and implantation energy of 100 keV. As implanted samples show a superparamagnetic behaviour attributed to the formation of Co clusters, room temperature ferromagnetism is attained after annealing at 800 °C, but no magnetoresistance was detected in the temperature range from 10 to 300 K.     

Nanowire growth on Si wafers by oxygen implantation and annealing

We report on nanowire formation on oxygen implanted Si wafers. In this method, a Si wafer is first oxygen-implanted and then annealed at high temperatures in Ar ambient to promote growth of nanowires with high aspect ratio. Their lengths range from several micrometers to thousands of micrometers and their diameters range from tens of nanometers to a few microns.     

Anomalous defect drift induced in semiconductor crystals at ion implantation and pulsed laser annealing

Variations of nonequilibrium carriers' lifetime in ion implanted silicon and germanium single crystal plates are observed and studied by means of microwave photoconductivity. Sufficient changes are detected at a long distance of 1–10 mm from the region of direct action of an ion beam in the plate plane. Also investigated is the influence of pulsed laser annealing of the ion-implanted silicon and germanium surfaces on nonequilibrium carriers' lifetime. Discussed are the pronounced anisotropy of the sideways long-range effect of ion implantation and a possible mechanism of defect dynamics associated with the dislocation drift.     

Characterization of low-resistance ohmic contacts to heavily carbon-doped n-type InGaAsBi films treated by rapid thermal annealing

Carbon-doped In Ga As Bi films on In P:Fe(100)substrates have been grown by gas source molecular beam epitaxy(GSMBE).The electrical properties and non-alloyed Ti/Pt/Au contact resistance of n-type carbon-doped In Ga As Bi films were characterized by Van der Pauw-Hall measurement and transmission line method(TLM)with and without rapid thermal annealing(RTA).It was found that the specific contact resistance decreases gradually with the increase of carrier concentration.The electron concentration exhibits a sharp increase,and the specific contact resistance shows a noticeable reduction after RTA.With RTA,the In Ga As Bi film grown under CBr4 supply pressure of 0.18 Torr exhibited a high electron concentration of 1.6×10²¹ cm^-3 and achieved an ultra-low specific contact resistance of 1×10^-8Ω·cm²,revealing that contact resistance depends greatly on the tunneling effect.     

Effect of strain on the carrier mobility in heavily doped p-type Si

We present an experiment that gives insight into the origin of the dependence of the hole mobility (mu) on the dopant species in heavily doped p-type Si under low electrical field. The Hall carrier concentration and mobility were measured in Si coimplanted with B and Ga in the 0.1-2 x 10{20} cm{-3} concentration range. The strain induced by substitutional dopants, detected by high resolution x-ray diffraction, was varied by changing the relative B and Ga concentration. The effect of strain on mobility was disentangled and a linear relationship between 1/mu and the perpendicular strain was found.