L. F. Makarenko

Investigation of point and extended defects in electron irradiated silicon—Dependence on the particle energy

This work is focusing on generation, time evolution, and impact on the electrical performance of silicon diodes impaired by radiation induced active defects. n-type silicon diodes had been irradiated with electrons ranging from 1.5 MeV to 27 MeV. It is shown that the formation of small clusters starts already after irradiation with high fluence of 1.5 MeV electrons. An increase of the introduction rates of both point defects and small clusters with increasing energy is seen, showing saturation for electron energies above ∼15 MeV. The changes in the leakage current at low irradiation fluence-values proved to be determined by the change in the configuration of the tri-vacancy (V3). Similar to V3, other cluster related defects are showing bistability indicating that they might be associated with larger vacancy clusters. The change of the space charge density with irradiation and with annealing time after irradiation is fully described by accounting for the radiation induced trapping centers. High resolution ...

Reactions of interstitial carbon with impurities in silicon particle detectors

We present deep level transient spectroscopy (DLTS) data measured on very high resistivity n-type float-zone silicon detectors after irradiation with 6MeV electrons. The carbon interstitial annealing kinetics is investigated as a function of depth in the detector structure and related to the inhomogeneous depth distribution of oxygen and carbon impurities in the devices. We compare our results with data published in previous works and point out some possible misinterpretation of DLTS data due to detector processing induced inhomogeneous distribution of impurities. Finally, we present a method to determine the absolute concentration of the oxygen and carbon impurities as functions of depth in devices by carefully analyzing the carbon interstitital annealing kinetics.

Interstitial Carbon Related Defects in Low-Temperature Irradiated Si: FTIR and DLTS Studies

The evolution of radiation-induced carbon-related defects in low temperature irradiated oxygen containing silicon has been studied by means of Fourier transform infrared absorption spectroscopy (FTIR) and deep level transient spectroscopy (DLTS). FTIR measurements have shown that annealing of interstitial carbon atom Ci, occurring in the temperature interval 260-300 K, results in a gradual appearance of a number of new absorption bands along with the well known bands related to the CiOi complex. The new bands are positioned at 812, 910.2, 942.6, 967.4 and 1086 cm-1. It has been found that the pair of bands at 910 and 942 cm-1 as well as another set of the bands at 812, 967.4 and 1086 cm-1 display identical behavior upon isochronal annealing, i.e. the bands in both groups appear and disappear simultaneously. The disappearance of the first group occurs at T = 285-300 K while the second group anneals out at T = 310-340 K. These processes are accompanied by an increase in intensity of the bands related to CiOi. It is suggested that intermediate states (precursors) are formed upon the transformation from a single (isolated) Ci atom to a stable CiOi defect. The results obtained in DLTS studies are in agreement with the FTIR data and show unambiguously the formation of CiOi precursors with slightly lower activation energy for the hole emission as compare to that for the main CiOi state.

Formation and annealing of boron-oxygen defects in irradiated silicon and silicon-germanium n+–p structures

New findings on the formation and annealing of interstitial boron-interstitial oxygen complex (BiOi) in p-type silicon are presented. Different types of n+−p structures irradiated with electrons and alpha-particles have been used for DLTS and MCTS studies. Electronic excitation essentially changes the formation rate of BiOi. It has been found that the increase of oxygen content slows the BiOi annealing rate down. The activation energy of the BiOi dissociation has been determined and it was found that germanium doping does not change the activation energy.

DLTS Studies of Carbon Related Complexes in Irradiated N- and P-Silicon

DLTS studies of transformation kinetics of different carbon–related complexes in electron irradiated n- and p-type silicon have been performed. It has been found that silicon self-interstitials have very low mobility even at room temperature in p-Si, but become extremely mobile under elec-tron injection. It is shown that upon annealing of interstitial carbon in p-Si a metastable state for interstitial carbon-interstitial oxygen complex is formed. This state has an energy level of about Еv+0.36 eV. The formation of the stable and metastable states takes place concurrently. The observed features of the carbon-related complexes formation are likely related to the existence of different crystallographic orientation of the equiprobable pathways through which the interstitial carbon and oxygen atoms can approach each other.

An explanation of electronic structure for thermal double donors in silicon

Abstract A model of two donor centers is suggested to explain electronic structure of thermal double donors in silicon. The model consistently explains the two valley structure of the ground state, the splitting of the 2 p ± -levels and other data obtained from infra-red absorption investigations of these defects.

Kinetics of cluster-related defects in silicon sensors irradiated with monoenergetic electrons

This work focuses on the kinetic mechanisms responsible for the annealing behavior of radiation cluster-related defects with impact on the electrical performance of silicon sensors. Such sensors were manufactured on high resistivity n-type standard float-zone (STFZ) and oxygen enriched float-zone (DOFZ) material and had been irradiated with mono-energetic electrons of 3.5 MeV energy and fluences of 3 × 1014 cm−2 and 6 × 1014 cm−2. After irradiation, the samples were subjected either to isochronal or isothermal heat treatments in the temperature range from 80 °C to 300 °C. The specific investigated defects are a group of three deep acceptors [H(116 K), H(140 K), and H(152 K)] with energy levels in the lower half of the band gap and a shallow donor E(30 K) with a level at 0.1 eV below the conduction band. The stability and kinetics of these defects at high temperatures are discussed on the basis of the extracted activation energies and frequency factors. The annealing of the H defects takes place similarly in both types of materials, suggesting a migration rather than a dissociation mechanism. On the contrary, the E(30 K) defect shows a very different annealing behavior, being stable in STFZ even at 300 °C, but annealing-out quickly in DOFZ material at temperatures higher than 200 °C , with a high frequency factor of the order of 1013 s−1. Such a behavior rules out a dissociation process, and the different annealing behavior is suggested to be related to a bistable behavior of the defect.This work focuses on the kinetic mechanisms responsible for the annealing behavior of radiation cluster-related defects with impact on the electrical performance of silicon sensors. Such sensors were manufactured on high resistivity n-type standard float-zone (STFZ) and oxygen enriched float-zone (DOFZ) material and had been irradiated with mono-energetic electrons of 3.5 MeV energy and fluences of 3 × 1014 cm−2 and 6 × 1014 cm−2. After irradiation, the samples were subjected either to isochronal or isothermal heat treatments in the temperature range from 80 °C to 300 °C. The specific investigated defects are a group of three deep acceptors [H(116 K), H(140 K), and H(152 K)] with energy levels in the lower half of the band gap and a shallow donor E(30 K) with a level at 0.1 eV below the conduction band. The stability and kinetics of these defects at high temperatures are discussed on the basis of the extracted activation energies and frequency factors. The annealing of the H defects takes place similarly ...

Formation and annealing of metastable (interstitial oxygen)-(interstitial carbon) complexes in n - and p -type silicon

It is shown experimentally that, in contrast to the stable configuration of (interstitial carbon)-(interstitial oxygen) complexes (CiOi), the corresponding metastable configuration (CiOi*) cannot be found in n-Si based structures by the method of capacitance spectroscopy. The rates of transformation CiOi* →CiOi are practically the same for both n- and p-Si with a concentration of charge carriers of no higher than 1013 cm−3. It is established that the probabilities of the simultaneous formation of stable and metastable configurations of the complex under study in the case of the addition of an atom of interstitial carbon to an atom of interstitial oxygen is close to 50%. This is caused by the orientation dependence of the interaction potential of an atom of interstitial oxygen with an interstitial carbon atom, which diffuses to this oxygen atom.

Effect of electron injection on defect reactions in irradiated silicon containing boron, carbon, and oxygen

Comparative studies employing Deep Level Transient Spectroscopy and C-V measurements have been performed on recombination-enhanced reactions between defects of interstitial type in boron doped silicon diodes irradiated with alpha-particles. It has been shown that self-interstitial related defects which are immobile even at room temperatures can be activated by very low forward currents at liquid nitrogen temperatures. Their activation is accompanied by the appearance of interstitial carbon atoms. It has been found that at rather high forward current densities which enhance BiOi complex disappearance, a retardation of Ci annealing takes place. Contrary to conventional thermal annealing of the interstitial boron-interstitial oxygen complex, the use of forward current injection helps to recover an essential part of charge carriers removed due to irradiation.

Effect of the energy of bombarding electrons on the conductivity of n-4H-SiC (CVD) epitaxial layers

The electrical characteristics of epitaxial layers of n-4H-SiC (CVD) irradiated with 0.9 and 3.5MeV electrons are studied. It is shown that the donor removal rate becomes nearly four times higher as the energy of impinging electrons increases by a factor of 4, although the formation cross section of primary radiation defects (Frenkel pairs in the carbon sublattice) responsible for conductivity compensation of the material is almost energy independent in this range. It is assumed that the reason for the observed differences is the influence exerted by primary knocked-out atoms. First, cascade processes start to manifest themselves with increasing energy of primary knocked-out atoms. Second, the average distance between genetically related Frenkel pairs grows, and, as a consequence, the fraction of defects that do not recombine under irradiation becomes larger. The recombination radius of Frenkel pairs in the carbon sublattice is estimated and the possible charge state of the recombining components is assessed.