scispace - formally typeset
Search or ask a question
Journal ArticleDOI

Electrically active defects due to end-of-ion-range damage in silicon irradiated with MeV Ar+ ions

TL;DR: In this article, the authors reported the occurrence of mid-gap acceptor levels using DLTS and TATS in a region well beyond the ion range, indicating that these deep levels are associated with point defects with local disorder in the neighbourhood.
Abstract: Damage induced by MeV Ar+ ion implantation and end of range defects in Si have been studied by capacitance-voltage, thermally stimulated capacitance, deep level transient spectroscopy (DLTS) and time analyzed transient spectroscopy (TATS). Unlike earlier studies, which focus on defects induced during post-implantation annealing steps, we study as-implanted p-type silicon samples. We report the occurrence of mid-gap acceptor levels using DLTS and TATS in a region well beyond the ion range. The presence of temperature dependent series resistance due to damaged region distorts DLTS lineshapes, even leading to sign reversal of DLTS peaks in some cases. A new and better method of correcting series resistance effects in capacitance transients has been employed. It is based on detecting the point of inversion of isothermal transients which are nonmonotonic due to the presence of series resistance. The capture process is found to be thermally activated with a high barrier energy. Possible origin of capture barrier and broadening in activation energy are discussed. Our results indicate that these deep levels are associated with point defects with local disorder in the neighbourhood.
Citations
More filters
Journal ArticleDOI
TL;DR: In this article, NPN transistors have been irradiated by 60 MeV oxygen ions in a fluence ranging from 5.0 to 1.3 ions/cm2, and the results obtained on the activation energy, density of trap levels, apparent capture cross section, introduction rate and space charge layer lifetime of different defects for different total fluence are presented and discussed.
Abstract: NPN transistors have been irradiated by 60 MeV oxygen ions in a fluence ranging from 5 × 1010 to 1 × 1013 ions/cm2. The DC current gain (hFE), excess base current ( Δ I B =I B post −I B pre ), excess collector current ( Δ I C =I C post −I C pre ) and collector saturation current (I C Sat ) of the ion irradiated transistors were studied systematically. The hFE of the transistors were found to be decreased drastically after ion irradiation. A significant increase has been observed in the collector current (IC) along with the increase in the base current (IB) after ion irradiation. The I C Sat of the ion irradiated transistors were also decreased significantly after irradiation. The radiation induced trap levels in the collector base depletion region of NPN transistors were studied by deep level transient spectroscopy technique and different types of trap levels were observed. The results obtained on the activation energy, density of trap levels, apparent capture cross section, introduction rate and space charge layer lifetime of different defects for different total fluence are presented and discussed.

30 citations

Journal ArticleDOI
TL;DR: In this article, the ion-irradiated transistors of NPN transistors were studied by employing the deep level transient spectroscopy technique and different types of trap levels were observed.
Abstract: NPN transistors were irradiated by 95 MeV oxygen ions in a fluence ranging from 5 × 1010 to 5 × 1012 ions cm−2. The dc current gain (hFE), excess base current (ΔIB = IBpost − IBpre), excess collector current (ΔIC = ICpost − ICpre) and collector-saturation current (ICS) of the ion-irradiated transistors were studied systematically. We found that both hFE and ICS of the transistors decrease drastically after ion irradiation. Secondly, a significant increase in the collector current (IC) along with the increase in the base current (IB) after ion irradiation was observed. The radiation-induced trap levels in the collector–base depletion region of NPN transistors were studied by employing the deep level transient spectroscopy technique and different types of trap levels were observed. The results obtained on the activation energy, density of trap levels, apparent capture cross section of the defects, introduction rate and space charge layer lifetime of different defects for different total fluence are presented and discussed.

26 citations

Journal ArticleDOI
TL;DR: In this article, the authors used deep level transient spectroscopy (DLTS), minority carrier transient spectrograms (SCTS), Laplace DLTS, and photoluminescence lifetime measurements to study recombination active defects in nitrogen-doped and nitrogen-lean n-type FZ-Si samples.
Abstract: Float zone silicon (FZ-Si) is typically assumed to be an extremely high quality material, with high minority carrier lifetimes and low concentrations of recombination active defects. However, minority carrier lifetime in FZ-Si has previously been shown to be unstable following thermal treatments between 450 and 700 °C, with a range of unidentified deep level states being linked to reduced carrier lifetime. There are suspicions that nitrogen doping, which occurs from the growth atmosphere, and intrinsic point defects play a role in the degradation. This study aims to address this by using deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy, Laplace DLTS, and photoluminescence lifetime measurements to study recombination active defects in nitrogen-doped and nitrogen-lean n-type FZ-Si samples. We find that nitrogen-doped samples experience increased degradation due to higher concentrations of deep level defects during thermal treatments compared to nitrogen-lean samples. In an attempt to explain this difference, in-diffusion of nickel has been used as a marker to demonstrate the existence of higher vacancy concentrations in the nitrogen-doped samples. The origin of the recombination active defects responsible for the thermally induced lifetime degradation in FZ-Si crystals is discussed.Float zone silicon (FZ-Si) is typically assumed to be an extremely high quality material, with high minority carrier lifetimes and low concentrations of recombination active defects. However, minority carrier lifetime in FZ-Si has previously been shown to be unstable following thermal treatments between 450 and 700 °C, with a range of unidentified deep level states being linked to reduced carrier lifetime. There are suspicions that nitrogen doping, which occurs from the growth atmosphere, and intrinsic point defects play a role in the degradation. This study aims to address this by using deep level transient spectroscopy (DLTS), minority carrier transient spectroscopy, Laplace DLTS, and photoluminescence lifetime measurements to study recombination active defects in nitrogen-doped and nitrogen-lean n-type FZ-Si samples. We find that nitrogen-doped samples experience increased degradation due to higher concentrations of deep level defects during thermal treatments compared to nitrogen-lean samples. In an a...

21 citations

Journal ArticleDOI
TL;DR: In this article, an investigation of electron traps in n-GaN, grown on sapphire by metal organic vapour phase epitaxy, by using charge deep level transient spectroscopy (Q -DLTS) is reported.
Abstract: We report investigation of electron traps in n-GaN, grown on sapphire by metal organic vapour phase epitaxy, by using charge deep level transient spectroscopy (Q -DLTS). Measurements have been made isothermally by rate window scanning over the temperature range 300–370 K and for rate windows in the range 105 s–1 to 1 s–1. Two traps are observed in this range with (i) activation energies ∼0.58 eV and ∼0.45 eV and (ii) capture cross sections ∼2 × 10–15 cm2 and ∼3 × 10–19 cm2 respectively. The first of these defects has been observed in all of the DLTS investigations reported in the literature. However, the second trap has not been seen in majority of the earlier reports. Possible reasons for this difference are discussed. (© 2008 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)

12 citations

Journal ArticleDOI
TL;DR: In this article, the authors studied electrically active defects in buried layers, produced by heavy ion implantation in silicon, using both conventional DLTS and an isothermal spectroscopic technique called time analyzed transient spectroscopy operated in constant capacitance mode (CC-TATS).
Abstract: We have studied electrically active defects in buried layers, produced by heavy ion implantation in silicon, using both conventional deep level transient spectroscopy (DLTS) and an isothermal spectroscopic technique called time analyzed transient spectroscopy operated in constant capacitance mode (CC-TATS). We show that CC-TATS is a more reliable method than DLTS for characterization of the heavily damaged buried layers. The major trap produced in the buried layers in p-type Si by MeV Ar+ implantation is found to have an energy level at Ev+0.52 eV. This trap, believed to be responsible for compensation in the damaged layer, shows exponential capture dynamics. We observed an unusually high thermal activation energy for capture, which is attributed to a macroscopic energy barrier for carriers to reach the buried layer. We observe two other majority carrier traps, and also a minority carrier trap possibly due to inversion within the depletion layer.

7 citations

References
More filters
Journal ArticleDOI
TL;DR: In this paper, a classification scheme for implant-related damage which arise upon annealing consisting of five categories is presented, and the most common forms of this damage are microtwins, hairpin dislocations and segregation related defects.
Abstract: A classification scheme for the different forms of implant-related damage which arise upon annealing consisting of five categories is presented. Category I damage is “subthreshold” damage or that which results prior to the formation of an amorphous layer. If the dose is increased sufficiently to result in the formation of an amorphous layer then the defects which form beyond the amorphous/crystalline (a/c) interface are classified as category II (“end of range”) damage. Category III defects are associated with the solid phase epitaxial growth of the amorphous layer. The most common forms of this damage are microtwins, hairpin dislocations and segregation related defects. It is possible to produce a buried amorphous layer upon implantation, If this occurs, then the defects which form when the two a/c interfaces meet are termed category IV (“clamshell”, “zipper”) defects. Finally, category V defects arise from exceeding the solid solubility of the implanted species in the substrate at the annealing temperature. These defects are most often precipitates or dislocation loops.

478 citations

Journal ArticleDOI
TL;DR: Comparison of the deep-level transient spectroscopy (DLTS) and EPR results allowed tentative identification of the different DLTS lines with particular EPR spectra, and thus conclusions about the microscopic models for different defects were reached.
Abstract: Energy levels of defect states introduced by plastic deformation of n-type silicon have been studied by capacitance transient spectroscopy. From the observed properties of the defects, it is concluded that two different types of defects are produced. The first type is interpreted as point defects located in the vicinity of, or inside, dislocations. These deep-level defects have been analyzed in a model involving level broadening due to strain fields and/or defect interaction. The analysis gives information on thermal emission rates, capture cross sections, ionization energies, and deep-level broadenings. In addition, this analysis allows for the determination of accurate defect concentrations. From the improved concentration measurements it has been possible to determine the dependence of the repulsive potential (responsible for the unusual capture mechanism) on the filling times during the capture process. The second type of defects seems to be directly related to dislocations, but their physical properties could not be determined unambiguously. Comparison of the deep-level transient spectroscopy (DLTS) and EPR results allowed tentative identification of the different DLTS lines with particular EPR spectra, and thus conclusions about the microscopic models for different defects. The quantitative comparison of defect concentrations measured by DLTS and EPR also suggests that in strongly deformed silicon, part of the EPR lines might be broadened due to imperfections in the lattice surrounding the paramagnetic center.

266 citations

Journal ArticleDOI
Sjoerd Roorda, S. Doorn, W.C. Sinke, P. M. L. O. Scholte1, E. J. van Loenen1 
TL;DR: Differential scanning calorimetry of amorphous silicon (a-Si) prepared by ion implantation shows a one-time low-temperature heat release, equal to one-third of the heat of crystallization as mentioned in this paper.
Abstract: Differential scanning calorimetry of amorphous silicon (a-Si) prepared by ion implantation shows a one-time low-temperature heat release, equal to one-third of the heat of crystallization. This heat release is direct evidence for structural relaxation of a-Si. It is in agreement with predictions made on the basis of Raman spectrometry.

189 citations

Journal ArticleDOI
James F. Ziegler1
TL;DR: In this paper, a review is made of proposed circuit structures which involve deep ion implantation, such as deep buried bipolar collectors fabricated without epitaxy, barrier layers to reduce FET memory sensitivity to soft-fails, CMOS isolation well structures, MeV implantation for customization and correction of completed circuits and graded reach-throughs to deep active device components.
Abstract: High energy ion implantation offers the oppertunity for unique structures in semiconductor processing. The unusual physical properties of such implantations are discussed as well as the special problems in masking and damage annealing. A review is made of proposed circuit structures which involve deep implantation. Examples are: deep buried bipolar collectors fabricated without epitaxy, barrier layers to reduce FET memory sensitivity to soft-fails, CMOS isolation well structures, MeV implantation for customization and correction of completed circuits and graded reach-throughs to deep active device components.

125 citations

Journal ArticleDOI
TL;DR: In this article, the authors pointed out that depending on the value of the sample resistance in series with the diode capacitance, the DLTS signal can be strongly reduced and even its sign may be reversed, entailing a possible confusion between majority and minority carrier traps.
Abstract: Peculiar features of Deep Level Transient Spectroscopy (DLTS) measurements on resistive samples are pointed out Depending on the value of the sample resistance in series with the diode capacitance, the DLTS signal can be strongly reduced and even its sign may be reversed, entailing a possible confusion between majority and minority carrier traps Means of detecting these effects are discussed and a correction procedure is proposed, based on varying the circuit impedance by means of an additional resistance in series with the sample Illustrative examples include ion implanted silicon and the case of a germanium bicrystal

97 citations