Radiation Defect Profiles Research Articles

Investigation of the switching and carrier recombination characteristics in the proton irradiated and thermally annealed Si PIN diodes

Results of comparative study of deep level transient spectroscopy and of reverse recovery time (RR) of PIN diodes with δ-and triangle-shape radiation defect distribution profiles are presented. FZ silicon PIN diodes were irradiated by varying proton fluence in the range of 1013–1015 p/cm2 and keeping fixed or gradually changing protons energy in the range of 2–2.7 MeV to introduce different profiles of radiation defects. Variations of the functional characteristics of PIN diodes containing different density of radiation defects and their distribution profiles are compared. Isochronous 24 h annealings in the temperature range of 80–400°C have been performed in order to suppress the detrimental carrier generation centres Keywords: reverse recovery time, deep level transient spectroscopy, radiation defects, carrier lifetime, Si PIN diodes

Platinum in-diffusion controlled by radiation defects for advanced lifetime control in high power silicon devices

The low-temperature (∼700 °C) in-diffusion of platinum (Pt) into the n-type float zone silicon guided and enhanced by radiation damage produced by implantation of helium ions was used to shape the profile of ideal recombination centers—platinum substitutionals (Pt s). Implantation of helium ions with energies up to 11 MeV introducing different profiles of radiation defects were applied for this purpose. Both the platinum silicide (PtSi) and implanted Pt layers were compared as the sources of Pt diffusion. The full-depth distribution of in-diffused Pt was studied by monitoring the acceptor level of Pt s −/0 ( E C − E T = 0.23 eV) by the current transient spectroscopy. Results show that the helium implantation significantly enhances platinum diffusion and allows its control up to the depths of hundreds of micrometers. The resulting Pt s distribution can be controlled by the profile of radiation damage produced by helium ions while the amount of in-diffused Pt s is set by the dose of platinum implantation. Application of the method using both the implanted and PtSi sources is demonstrated on optimization of turn-off properties of high power PiN diodes.

Radiation enhanced diffusion of implanted platinum in silicon guided by helium co-implantation for arbitrary control of platinum profile

The in-diffusion of platinum into a low-doped n-type float zone silicon guided and enhanced by radiation damage produced by co-implantation of helium ions was investigated. The implantation of 1MeV platinum ions at different doses ranging from 5×1011 to 5×1012cm−2 was used to produce a finite source for platinum diffusion. Single and multiple energy implantation of helium ions with energies 7, 9, 11 and 13MeV introducing different profiles of radiation defects were applied to enhance and shape the diffusion of platinum atoms performed by 20min annealing at 725°C in vacuum. The distribution of in-diffused platinum was studied by monitoring the acceptor level of substitutional platinum Pts-/0 (EC−ET=0.23eV) by deep level transient spectroscopy. Results show that the helium co-implantation significantly enhances platinum diffusion and allows its control up to the depths of hundreds of micrometers. The resulting Pts distribution is given by the profile of radiation damage produced by helium ions while the amount of in-diffused Pts can be controlled by the dose of platinum implantation. It is also shown that an extra annealing at 685°C performed prior to helium implantation substantially increases the amount of in-diffused platinum.

A model for the prediction of radiation defect profiles in the semiconductor target (HgCdTe) subjected to high power short pulsed ion beams

A mathematical model to describe processes occurring during the irradiation of semiconductor materials with high power pulsed ion beams is proposed. The model takes account of recombination between vacancies and interstitial atoms and the formation of defect complexes and these processes are analysed and discussed. The effect of an inhomogeneous non-stationary temperature field and mechanical quasi-static and dynamic stress fields on radiation defect profiles is also examined. Spatial profiles of the charge carrier concentration and the implanted ion distribution are calculated and a comparison made with experimental profiles obtained for the semiconductor compound Hg1−xCdxTe. The results show that the defect concentration profiles near the surface are reduced with a large rate of recombination between vacancy and interstitial atoms.

Accurate Identification of Radiation Defect Profiles in Silicon after Irradiation with Protons and Alpha-Particles in the MeV Range

Accurate Identification of Radiation Defect Profiles in Silicon after Irradiation with Protons and Alpha-Particles in the MeV Range

Calculations of Radiation-Induced Defect Profiles in CdHgTe Crystals Exposed to Ion Pulses

The formation and evolution of the radiation-defect profiles in CdHgTe crystals exposed to high-power ion pulses is examined. A mathematical model for radiation-defect formation allowing for the effects of an inhomogeneous nonstationary temperature field and mechanical quasi-static and dynamic stress fields is discussed. Examples of calculations are given, and the calculated and experimental data are compared.

Defect distribution in MeV proton irradiated silicon measured by high-voltage current transient spectroscopy

Current transient spectroscopy (CTS) using high relaxation voltages up to 1 kV is shown to be an effective tool for non-destructive characterization of radiation defect profiles in silicon resulting from the MeV ion irradiation. The method was used for profiling of different defect centers produced in low-doped, float zone, n-type silicon by irradiation with 3, 4 and 5.3 MeV protons to a fluence of 5×10 9 and 1×10 10cm −2. The results were compared with those obtained from capacitance DLTS and reverse I– V profiling. Electronic properties and introduction rates of dominant defect centers were also established. It is shown that CTS is capable to trace full-depth profiles of dominant radiation defects and provide precise and more accurate data than previously presented by destructive profiling procedures. Measured distributions of vacancy related radiation defects agree well with the distribution of the primary damage received from Monte Carlo simulations with the exception of the peak broadening attributed to vacancy diffusion.

Divacancy profiles in MeV helium irradiated silicon from reverse I–V measurement

The application of high-voltage reverse current to voltage characteristics for characterization of ultra-deep radiation defect profiles in ion irradiated silicon p-i-n diodes is presented. Theoretical analysis shows that monitoring of the reverse current gradient with increasing bias can give, in combination with Deep Level Transient Spectroscopy (DLTS) and Capacitance–Voltage (C–V) measurement, quantitative information about the distribution of generation defect centres with the highest emissivity. The method is subsequently used for characterization of deep-level profiles in p +pnn + power diodes irradiated by He 2+ ions with energies 11–22 MeV and fluences 2.5 × 10 9–1.2 × 10 10 cm −2. The results show that the method can non-destructively determine the concentration profile of divacancies, the dominant generation centre in helium irradiated silicon, in the depths of the device where application of other methods usually fails.

Interaction of high-energy ion beams with crystals

The depth distribution of impurities and defects at high-energy ion implantation is studied experimentally and with the help of calculations based on transport equations. The doping profile after implantation of silicon with boron ions with an energy of 92 MeV is determined by measuring the layer resistance, and the profiles of radiation defects are determined by the measurements of photoluminescence yield and with the help of optical microscopy. The theoretical calculations correctly forecast mean ion ranges, but the form of experimental doping profiles is distorted by channeling. The observed distribution of defects over the projected range cannot be explained by the distribution of recoil atoms immediately after the cascade passage.

Study of defect annealing by supercurrent proton beam irradiation and of radiation defect profiles in GaAs by the positron annihilation method

The annealing of radiation defects in GaAs by a supercurrent proton beam with currents up to 200 A cm −2 and 4.8 MeV energy was studied. The positron annihilation method (measurement of angular distribution of annihilation photons) has been used to study the depth profiles of radiation defects in solids. Profiles of vacancy-type defects in GaAs irradiated by a supercurrent proton beam have been measured.

Channeled ion implantation of as+ in silicon at 300°c

Abstract Spatial distribution and lattice location of implanted As atoms in and Si as well as spatial distribution of radiation defects were studied by the RBS techniques after channeled implantation of 30 keV As+ ions with a dose of 3 × 1015 cnr2 at 300°C. The profile of As atoms was observed to have two maxima due to superposition of the profiles of initially nonchanneled and dechanneled ions. The aligned As+ ion beam generates fewer defects than the random one. The radiation defect profiles both after channeled and random implantations at 300°C are of the well pronounced bimodal type with a minimum at the depth of the maximum of elastic energy losses of nonchanneled As+ ions. A model of the layer of disordered zones with vacancy-defect nuclei and interstitial-defect shells is proposed. Annealing by a ruby laser with a pulse energy density of 1 J/ cm2 and duration 40 ns results in removal of the radiation defects and flattening of the substitutional As atom profile.

Generation of secondary electrons and radiation defects in matter during absorption of electrons with energy above 1 MeV

Using the model of sections with one-dimensional geometry, the output of δ electrons generated by electrons with energies from 1 to 10 MeV is considered as a function of the thickness and the atomic number of various absorbers. The depth distributions of thermalized electrons and radiation defect profiles are calculated for the model absorbers KCl and NaCl. Radiation defects due to irreversible displacement of lattice atoms upon elastic scattering of rapid electrons are considered. The microphotometry method is used to obtain depth distributions of enrichment centers in the ionic crystals KCl and NaCl for irradiation by electrons with energies E=1, 1.5, and 2 MeV for electron-beam incidence on the absorbers at angles ofΘ0=0, 20, 45°. The integral density of the incident beam was varied from 1·1014 to 6·1015 cm−2. It was found that in ionic crystals the enrichment center density is proportional to the density of thermalized δ electrons, if the concentration of radiation defects generated is less than 1% of the density of preradiation anion vacancies.

2111. Profiles of radiation defects and implanted boron in silicon: N P Dikiy et al,Fiz Tekh Polup, 9 (3), 1975, 592–594 ( in Russian)

2111. Profiles of radiation defects and implanted boron in silicon: N P Dikiy et al,Fiz Tekh Polup, 9 (3), 1975, 592–594 ( in Russian)