ISSN 0020-1685, Inorganic Materials, 2007, Vol. 43, No. 11, pp. 1153–1159. © Pleiades Publishing, Inc., 2007. Original Russian Text © F.P. Korshunov, I.F. Medvedeva, L.I. Murin, V.P. Markevich, 2007, published in Neorganicheskie Materialy, 2007, Vol. 43, No. 11, pp. 1287–1294.
Effect of High-Temperature Heat Treatment on the Generation and Annealing of Radiation-Induced Defects in n-Type Silicon Crystals F. P. Korshunov, I. F. Medvedeva, L. I. Murin, and V. P. Markevich Joint Institute of Solid-State and Semiconductor Physics, Belarussian Academy of Sciences, ul. Brovki 19, Minsk, 220072 Belarus e-mail:
[email protected] Received July 14, 2006
Abstract—Defect formation and annealing processes in n-type silicon crystals heat-treated at temperatures from 550 to 1000°C for a short time and then gamma-irradiated in a 60Co source or electron-irradiated (E = 4 MeV) at room temperature have been studied using Hall effect measurements. The results demonstrate that the preheat treatment (PHT) has an insignificant effect on the energy spectrum and generation efficiency of major defect species. At the same time, PHT results in enhanced annealing of radiation-induced defects, accompanied by the formation of additional electrically active centers. PHT is assumed to activate transition-metal impurities (fast diffusers in silicon), which then interact with radiation-induced defects. DOI: 10.1134/S0020168507110015
INTRODUCTION The fabrication of silicon-based semiconductor devices includes a number of processing steps at elevated temperatures, which typically influence the defect chemistry of Si single crystals. For this reason, irradiation-induced defect formation processes in silicon-based structures may differ markedly from those in silicon crystals. Since radiation processing is widely used in the modern technology of silicon devices and integrated circuits [1, 2], knowledge of the preheat treatment (PHT) effect on the generation and annealing of radiation-induced defects (RIDs) in silicon is critical for these applications. Such studies have been carried out by a number of groups [3–12], but their results are in many respects inconsistent or even contradictory. Considerable research effort has been devoted to the effect of long-term (tens and hundreds of hours) PHT at temperatures from 600 to 1100°ë on the generation and annealing of RIDs in silicon [5–9]. Such PHTs lead to oxygen precipitation, considerably reducing the interstitial oxygen concentration in Czochralski-grown (CZ) silicon crystals, and may have a significant effect on irradiation-induced defect formation processes. In particular, Neimash et al. [6, 7] observed changes in the relative generation rates of vacancy–oxygen (A center) and vacancy–phosphorus (E center) defect complexes, which were attributed to the redistribution of vacancy (V) flows owing to the changes in interstitial oxygen concentration upon PHT at 1100°ë. In studies of the annealing behavior of RIDs in silicon preheat-treated at 600°ë, Shmalz et al. [8] and Emtsev et al. [9] found the annealing temperature of A centers to drop from 350 to
180–200°ë. This effect was interpreted under the assumption that the silicon interstitials (Sii) present in oxygen precipitates after the PHT were “liberated” at ~200°ë and then reacted with A centers according to the scheme V–é + Sii éi [8, 9]. The annealing temperature of A centers in silicon crystals was also reported to decrease as a result of short-term PHT in the range 550–1000°ë followed by rapid cooling [4, 10–12]. The effect of PHT was assumed to be associated with the activation of hydrogen and transition-metal impurities (fast diffusers in silicon) and subsequent interaction of these impurities with RIDs. In the present work, this issue is addressed in greater detail. EXPERIMENTAL We studied CZ and float-zone (FZ) n-type Si crystals with phosphorus concentrations in the range NP = (4–50) × 1013 cm–3. The FZ Si was grown in an argon atmosphere. The oxygen and carbon concentrations were NO = (6–9) × 1017 cm–3 and NC = (1–5) × 1016 cm–3 in the CZ Si and NO ≅ (1–3) × 1016 cm–3 and NC ≤ 1 × 1016 cm–3 in the FZ Si, as determined by optical measurements. The crystals were heat-treated in the range 500–1000°ë in air for 5–60 min and were then rapidly cooled ((≥100°C/s) by dropping into isopropanol. Some of the samples were annealed in ampules and were then cooled by rapidly immersing the ampules in water. The annealed and as-grown (control) crystals were gammairradiated in a 60ëÓ source or electron-irradiated (E = 4 MeV) at room temperature.
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Fig. 1. Electron concentration as a function of Fermi level position for CZ Si crystals with NP = 4.5 × 1013 cm–3: an asgrown crystal (1) was 60Co gamma-irradiated (3) and then annealed at 240°C (5); another crystal was preheat-treated at 600°C for 30 min (2), then 60Co gamma-irradiated (4), and also annealed at 240°C (6); irradiation to î = 6 × 1016 cm–2.
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Fig. 2. (1, 2, 2') Density of defects with a level at EC – 0.17 eV and (3) reduction in 300-K carrier concentration as functions of 30-min anneal temperature for CZ Si crystals (see Fig. 1): (1) control crystal, (2, 2', 3) after PHT; (2') see text.
The carrier concentration in the crystals was measured at temperatures from 77 to 400 K. The results were used to determine the concentrations and energy levels of electrically active defects. EXPERIMENTAL RESULTS CZ Si crystals 60ëÓ gamma-irradiated at ~50°ë. CZ Si crystals typically contain small amounts of dou-
bly charged oxygen-related thermal donors (with levels at EC – 0.07 eV and EC – 0.15 eV) [13], which form during postgrowth cooling. Heat treatment at t ≥ 600°ë eliminated such centers in our crystals (Fig. 1, curves 1, 2), without producing significant concentrations of additional electrically active centers with levels located above midgap. 60ëÓ gamma irradiation produced defects with levels near EC – 0.17 eV (D0.17) in both controls and preheat-treated crystals (Fig. 1, curves 3, 4). These levels were due, for the most part, to A centers and, to a lesser degree, to interstitial carbon–lattice carbon (ëi–ës) complexes [14] (these defect species are rather difficult to distinguish using electrical measurements). PHT had little or no effect on the D0.17 generation efficiency but significantly influenced the annealing behavior of these centers. Figure 2 illustrates the effect of 30-min anneals on the density of defects with a level at EC – 0.17 eV in an unheat-treated sample (curve 1) and a sample preheattreated at 600°ë before gamma-irradiation (curve 2). In the unheat-treated silicon, D0.17 annealing involves two steps: at 200–240 (poorly defined) and 300–380°ë (main). According to Makarenko et al. [4] and Murin [14], the first step is the annealing of the ëi–ës defect complex (see also Fig. 1, curve 5), and the second step is A-center annealing. Note that, in both steps, the formation of additional electrically active centers is insignificant. A qualitatively different annealing behavior of RIDs was observed in preheat-treated samples. The annealing temperature of A centers was reduced to 150– 220°ë, and their disappearance was accompanied by the formation of comparable concentrations of deep compensating centers (DCCs), which reduced the room-temperature carrier concentration (Fig. 2, curve 3). The acceptor level due to the DCCs was located at midgap (deeper than EC – 0.50 eV) or below midgap, as evidenced by the fact that those defects were not ionized up to the intrinsic region (Fig. 1, curve 6). The restoration of the carrier concentration due to the annealing of the DCCs took place in a wide temperature range, 260 to 400°ë. The process involved the formation (restoration) of a small amount of defects with a level at Eë – 0.17 eV and subsequent annealing of these defects (Fig. 2, curve 2'). PHTs at other temperatures in the range 527–827°ë had a similar effect (Figs. 3a, 3b). It can be seen that the effect of PHT was significant starting at 527°ë. The sample preheat-treated at this temperature had a reduced annealing temperature of D0.17, and some of these centers were replaced by DCCs. With increasing PHT temperature, the annealing temperature of D0.17 decreased, and almost all of these centers were replaced by DCCs. We also studied the influence of PHT time (5, 30, and 60 min at 700°ë) and cooling rate on the annealing INORGANIC MATERIALS
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Fig. 3. (a) Density of defects with a level at EC – 0.17 eV and (b) reduction in 300-K carrier concentration as functions of isochronal anneal temperature for (1) control and (2–6) preheat-treated CZ Si crystals (NP = 2 × 1014 cm–3) 60Co gamma-irradiated to î = 3 × 1017 cm–2; PHT temperature = (2) 527, (3) 577, (4) 627, (5) 727, (6) 827°ë.
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(Fig. 5b, curve 4), which had been shown earlier to contain hydrogen atoms [15, 16] and had been tentatively identified as H–Ci–Oi defect complexes [16, 17]. CZ and FZ Si crystals irradiated with fast electrons near 0°ë. Fast-electron irradiation of CZ Si crystals at 0°ë produces not only A centers but also carbon
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of the defects with a level at EC – 0.17 eV and the formation of DCCs. The PHT time (in the specified range) was found to have an insignificant effect on the enhanced annealing of A centers and the efficiency of DCC generation. At the same time, the rate of subsequent cooling had a marked effect on the efficiency of the conversion of A centers into DCCs. This is clearly illustrated by Fig. 4, which shows the D0.17 and DCC concentrations as functions of isochronal anneal temperature for two samples cut from the same wafer and preheat-treated at 700°ë for 30 min, but cooled at different rates: one sample was dropped into isopropanol (rapid cooling), and the other was immersed together with the ampule in water (slow cooling). Next, both samples were 60Co gamma-irradiated. In the sample cooled by dropping into isopropanol, the D0.17 annealing temperature was reduced to 150– 220°ë (Fig. 4, curve 1), and the D0.17 annealing was accompanied by the formation of comparable concentrations of DCCs (curve 3). In the samples cooled with the ampule (curves 2, 4), D0.17 annealing took place in a wide temperature range (200 to 350°ë), DCCs were formed at higher temperatures, and only some of the Ä centers converted to DCCs. Note that RIDs exhibited similar annealing behavior after PHT at 1000°ë and cooling of the sample by rapidly immersing the silica ampule in water. In that case, however, D0.17 annealing was accompanied not only by DCC generation but also by the formation of defects with levels at EC – 0.25–0.35 eV (Fig. 5a, curve 3; Fig. 5b, curves 2, 3). Just as the DCCs, those centers were annealed out in the range 275–350°ë. In addition, in this temperature range we observed the formation of low densities of defects with a level at EC – 0.075 eV
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Fig. 4. (1, 2) Density of defects with a level at EC – 0.17 eV and (3, 4) reduction in carrier concentration as functions of isochronal anneal temperature for CZ Si crystals with NP = 2 × 1014 cm–3 preheat-treated at 700°ë for 30 min and then cooled (1, 3) by dropping into isopropanol (rapid cooling) and (2, 4) by immersing together with the ampule in water (slow cooling), followed by 60Co gamma irradiation to î = 3.2 × 1017 cm–2.
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Fig. 5. (a) Electron concentration as a function of Fermi level position for CZ Si crystals with NP = 2 × 1014 cm–3 (1) preheat-treated at 1000°ë, (2) then 60Co gamma-irradiated to î = 3.2 × 1017 cm–2, and (3) annealed at 250°ë. (b) Densities of defects with levels at (1) EC – 0.17 eV, (3) EC – (0.25–0.35) eV, and (4) EC – 0.075 eV and (2) reduction in the carrier concentration measured at EF = EC – 0.17 eV as functions of isochronal anneal temperature for CZ Si crystals with NP = 2 × 1014 cm–3 preheat-treated at 1000°ë.
interstitials (with a level at EC – 0.12 eV) and divacancies (levels at EC – 0.2 eV and EC – 0.4 eV) [18]. Near room temperature, carbon interstitials in both unheattreated and preheat-treated crystals predominantly form ëi–éi defect complexes, which act as deep donors (with a level at EV + 0.35 eV [19]) and have no effect on the electron concentration in n-Si. The annealing behavior of A centers in crystals electron-irradiated after PHT is similar to that in gamma-irradiated Si. We found no conclusive evidence that PHT influenced the annealing behavior of divacancies. Nevertheless, pre-
liminary results indicated that their annealing temperature was also reduced, but, in contrast to A centers, the divacancies in n-type silicon converted to electrically inactive centers. Irradiation of FZ Si crystals produces V–P defect complexes (E centers) in addition to A centers, divacancies, and ëi. In the crystals with NP = 5 × 1014 cm–3, such complexes are generated with approximately the same efficiency as A centers. On the other hand, since the oxygen and carbon concentrations in these crystals differ little, ëi annealing is accompanied by the formation of both ëi–Oi and ëi–ës defect complexes, in comparable concentrations. As mentioned above, the ëi–ës complex has a level at EC – 0.17 eV. Accordingly, the formation of this complex at temperatures from 30 to 80°ë increases the net density of defects with a level at EC – 0.17 eV (Fig. 6a). In the temperature range 100– 150°ë, the density of such defects increases further, but this is due to the annealing of E centers (Fig. 6b) and the formation of additional A centers. PHT of FZ Si crystals at temperatures from 500 to 700°ë was found to have an insignificant effect on the annealing behavior of the ëi, E, and (in contrast to CZ Si) D0.17 centers. At higher temperatures (≥800°ë), the effect of PHT was similar to that in CZ Si (Figs. 6a, 6b, curves 3): the defects with a level at EC – 0.17 eV had a markedly reduced annealing temperature and partially converted to DCCs. A more detailed analysis of the temperature dependences of carrier concentration suggested that, most likely, only the A centers fully converted to DCCs, whereas the ëi–ës defect complexes and divacancies converted to electrically inactive centers. DISCUSSION The annealing temperature of RIDs in bulk crystals may decrease for two reasons. One reason is the formation (presence) of additional sinks for mobile RIDs, which accelerate RID annealing with no changes in the activation energy of the process. For example, ëi annealing in CZ Si crystals occurs at 0–30°C, whereas in FZ Si crystals, where the concentration of major sinks (oxygen and carbon) is far lower, Ci interstitials may persist up to 80–130°C. In both instances, however, the activation energy for Ci annealing is ~0.8 eV [20]. The other reason is the formation (presence) of mobile species capable of interacting with RIDs and converting them to a different state. One clear example of such a process is the interaction of hydrogen with RIDs [15–17, 21, 22]. The former process appears unlikely in crystals that have been subjected to short-term PHT. In this case, there are no changes in the state of oxygen (no precipitation) or carbon and no generation of any extended defects that would be capable of absorbing vacancies or INORGANIC MATERIALS
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Fig. 6. (a) Density of defects with a level at EC – 0.17 eV and (b) reduction in 300-K carrier concentration as functions of isochronal anneal temperature for (1) control and preheat-treated CZ Si crystals (NP = 5 × 1014 cm–3) irradiated with fast electrons to î = 1 × 1015 cm–2; PHT temperature = (2) 700 and (3) 800°C.
V–O complexes, as evidenced by the fact that heat treatment has no effect on the efficiency of irradiation-induced defect formation in CZ Si crystals. Moreover, the estimated activation energy for the conversion of A centers to DCCs is ~1 eV, whereas the activation energy for the conventional annealing of A centers is ~1.8 eV [22]. It appears more likely that PHT leads to the formation of electrically inactive defects mobile above 100°C and capable of interacting with RIDs. This assumption is supported by the fact that a 30-min additional anneal at temperatures from 200 to 300°ë markedly reduces the effect of PHT on the annealing behavior of RIDs in samples heat-treated before irradiation. Clearly, this is associated with the reduction in the density of mobile thermal defects upon heat treatment in the range 200– 300°ë. That such defects have high mobility is evidenced by the observed influence of cooling rate: the PHT effect was strongest after quenching. The nature of the mobile thermal defects is rather difficult to establish with certainty from available experimental data. Clearly, the mobile thermal defects are not native defects since the efficiency of their generation depends significantly on the growth process. Under identical PHT conditions, the density of mobile thermal defects, which can be evaluated from the DCC concentration, is much higher in CZ Si crystals compared to FZ Si. The density of native defects (V and Sii) in Si at ~800°ë is known to be no higher than 1013 cm–3 [23]. At the same time, in some of the CZ Si crystals the density of mobile thermal defects reacting with A centers reached (2–3) × 1014 cm–3 even at a PHT temperature as low as 600°C. INORGANIC MATERIALS
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It is reasonable to assume that the mobile thermal defects are fast diffusers (hydrogen, transition-metal, and other impurities). The concentration of these impurities in as-grown silicon crystals may be rather high [24], and most of them are usually in a bound state, in the form of various complexes (clusters) which have appeared during postgrowth cooling. Subsequent heat treatment followed by quenching reactivates the impurities [25], to the level of their solubility at the PHT temperature, which enables more active interaction with RIDs. This conclusion fits well with the results reported by You et al. [26], who observed similar annealing behavior of RIDs in Fe-doped crystals quenched from 1000°ë. In such crystals, A centers were annealed out at 100–150°ë, with the formation of defects with a level at EC – 0.36 eV, which were identified as V–O–Fe defect complexes [26]. Note that, in our experiments at t ≤ 827°ë, no RIDs with a level at EC – 0.36 eV were detected. Also, Fe atoms cannot be responsible for the formation of DCCs because, in the temperature range 600–800°C, the iron solubility in silicon is rather low (1014 cm–3) are copper and nickel [28]. These metals are among the most abundant residual impurities in CZ
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Si crystals. Moreover, according to Aboelfotoh and Svensson [29], copper may have a significant effect on the annealing behavior of RIDs in Si crystals irradiated with fast electrons. It is reasonable to assume that it is these impurities (Cu and Ni) which are responsible for the enhanced annealing of A centers and the formation of DCCs in the crystals preheat-treated at t ≤ 827°ë. The formation of defects with levels at EC – 0.25– 0.35 eV in the silicon crystals preheat-treated at 1000°ë is, most likely, associated with the introduction of V−O–H (EC – 0.32 eV) and V–O–Fe ((EC – 0.36 eV) electrically active defect complexes. That hydrogen interacts with RIDs is also evidenced by the formation of hydrogen-containing centers with a level at EC – 0.075 eV. The Fe solubility in Si at 1000°C is ~3 × 1014 cm–3, and this impurity may also participate in the formation of defects with levels at EC – 0.25–0.35 eV. CONCLUSIONS The present results demonstrate that short-term PHT at temperatures from 550 to 1000°ë has an insignificant effect on the energy spectrum and generation efficiency of major defect species in n-type silicon crystals under 60Co gamma irradiation or fast-electron irradiation at room temperature. At the same time, we observed enhanced annealing of RIDs in the preheattreated crystals, accompanied by the formation of additional electrically active centers. This effect was most pronounced in the CZ Si crystals rapidly cooled (quenched) after PHT. The annealing temperature of A centers in those crystals was as low as 100–150°ë, and the A centers converted to deep acceptors. The generation efficiency of the deep acceptors depends on the PHT temperature and cooling rate and, as a rule, varies from ingot to ingot. These observations, coupled with earlier results, lead us to conclude that the influence of PHT is associated primarily with the presence of residual unintentional transition-metal impurities (Cu, Ni, Fe, and others). In as-grown silicon crystals, most of them are usually in a bound state, in the form of various complexes (clusters) which have appeared during postgrowth cooling. Subsequent heat treatment followed by quenching reactivates the impurities, bringing them to interstitial sites (producing an interstitial solid solution at high temperatures) or to more weakly bound complexes, which allows them to more actively interact with RIDs. Even very low concentrations of transition-metal impurities may have a significant effect on the performance parameters of silicon structures [30, 31], notably reducing the yield to specification in the device manufacturing stage. The effect of such impurities cannot be fully eliminated even with the most advanced gettering techniques [32]. Therefore, the development of novel approaches for evaluating the transition-metal concentration in silicon crystals and structures continues to be a challenge in modern microelectronics. In this context,
radiation-stimulated activation of such impurities (conversion to an electrically active state) via annealing of irradiated Si crystals appears potentially attractive. This approach can be used to assess the impurity concentration in the working (active) region of p–n structures (e.g., in combination with DLTS measurements [33]). ACKNOWLEDGMENTS This work was supported in part by the Belarussian Foundation for Basic Research, project no. F06-291. REFERENCES 1. Korshunov, F.P., Bogatyrev, Yu.V., and Vavilov, V.A., Vozdeistvie radiatsii na integral’nye mikroskhemy (Radiation Effects in Integrated Circuits), Minsk: Nauka i Tekhnika, 1986. 2. Korshunov, F.P., Bogatyrev, Yu.V., Lastovskii, S.B., et al., Radiation Effects in Technology of Semiconductor Materials and Devices, in Aktual’nye problemy fiziki tverdogo tela (Critical Issues in Solid-State Physics), Minsk: Belaruskaya Navuka, 2003, pp. 245–268. 3. Berezina, G.M., Korshunov, F.P., and Raines, L.Yu., Defect Annealing in Quenched n-Type Silicon Irradiated with Fast Electrons, Izv. Akad. Nauk SSSR, Neorg. Mater., 1979, vol. 15, no. 7, pp. 683–686. 4. Makarenko, L.F., Markevich, V.P., Murin, L.I., and Tkachev, V.D., Interactions between Radiation-Induced and Quench-Induced Defects in Silicon, Dokl. Akad. Nauk BSSR, 1981, vol. 25, no. 11, pp. 988–990. 5. Bolotov, V.V., Karpov, A.V., Stuchinsky, V.A., and Schmalz, K., Accumulation of Radiation Defects in Oxygen-Rich n-Type Silicon Heat-Treated at Temperatures from 600 to 1000°C, Phys. Status Solidi A, 1986, vol. 96, no. 1, pp. 129–134. 6. Neimash, V.B., Sagan, T.R., Tsmots’, V.M., et al., Mechanisms behind the Effect of Heat Treatment on the Irradiation Behavior of Silicon, Ukr. Fiz. Zh. (Russ. Ed.), 1991, vol. 36, no. 9, pp. 1398–1403. 7. Neimash, V.B., Sagan, T.R., and Tsmots, V.M., On the Role of Uncontrolled Sinks in Silicon under Irradiation, Phys. Status Solidi A, 1991, vol. 123, pp. K95–K100. 8. Shmalz, R., Tittelbach, K., Emtsev, V.V., and Daluda, Yu.M., Effect of Oxygen Clustering at 600°C on the Annealing of A-Centers in CZ-Silicon, Phys. Status Solidi A, 1989, vol. 116, no. 1, pp. K37–K42. 9. Emtsev, V.V., Khramtsov, V.A., and Shmalz, R., On the A-Centre Formation in Heat-Treated Cz-Silicon, Phys. Status Solidi A, 1990, vol. 120, no. 1, pp. K15–K18. 10. Korshunov, F.P., Makarenko, L.F., Markevich, V.P., et al., Enhanced Annealing of Radiation Defects in PreHeat-Treated Si Crystals, Proc. Int. Conf. on the Science and Technology of Defect Control in Semiconductors (Jokohama, 1989), North-Holland: Elsevier, 1990, pp. 541–545. 11. Medvedeva, I.F., Makarenko, L.F., Markevich, V.P., and Murin, L.I., Annealing Behavior of Radiation-Induced Defects in Preheat-Treated Si Crystals, Izv. Akad. Nauk BSSR, Ser. Fiz.-Mat. Nauk, 1991, no. 3, pp. 19–24. INORGANIC MATERIALS
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EFFECT OF HIGH-TEMPERATURE HEAT TREATMENT 12. Medvedeva, I.F., Murin, L.I., Markevich, V.P., et al., Enhanced Annealing of Radiation-Induced Defects in Preheat-Treated n-Type CZ Si Crystals, Trudy 13-go mezhdunarodnogo soveshchaniya “Radiatsionnaya fizika tverdogo tela” (Proc. 13th Int. Conf. on Irradiation Effects in Solids), Sevastopol, 2003, pp. 425–429. 13. Coutinho, J., Jones, R., Murin, L.I., et al., Thermal Double Donors and Quantum Dots, Phys. Rev. Lett., 2001, vol. 87, no. 23, p. 235 501. 14. Murin, L.I., On the Nature of Interstitial Defect with EC – 0.16 eV Level in Irradiated Silicon, Phys. Status Solidi A, 1986, vol. 93, no. 2, pp. K147–K149. 15. Korshunov, F.P., Markevich, V.P., Medvedeva, I.F., and Murin, L.I., Electrically Active Hydrogen-Containing Defects in Irradiated Silicon, Dokl. Akad. Belarusi, 1994, vol. 38, no. 2, pp. 35–39. 16. Medvedeva, I.F., Murin, L.I., Markevich, V.P., and Komarov, B.A., Formation and Annealing of a Metastable Hydrogen-Containing Center in Irradiated CZ Si: Influence of Various Factors, Vopr. At. Nauki Tekh., Ser.: Fiz. Radiats. Povrezhdenii Radiats. Materialoved., 2001, no. 2, pp. 48–52. 17. Yarykin, N. and Weber, J., Formation of the D1-Center in Irradiated Silicon by Room-Temperature Hydrogenation, Phys. B (Amsterdam, Neth.) 2003, vols. 340–342, pp. 701–704. 18. Korshunov, F.P., Markevich, V.P., Medvedeva, I.F., and Murin, L.I., Acceptor Levels of Divacancies in Silicon, Fiz. Tekh. Poluprovodn. (S.-Peterburg), 1992, vol. 26, no. 11, pp. 2007–2011. 19. Murin, L.I., On the Electrical Activity of the Ci–Oi Complex in Silicon, Phys. Status Solidi A, 1987, vol. 97, no. 2, pp. K107–K110. 20. Markevich, V.P. and Murin, L.I., Selective Capture of Carbon Interstitials in Silicon, Fiz. Tekh. Poluprovodn. (Leningrad), 1988, vol. 22, no. 5, pp. 911–914. 21. Markevich, V.P., Murin, L.I., Suezawa, M., et al., Observation and Theory of V–O–H2 Complex in Silicon, Phys. Rev. B: Condens. Matter Mater. Phys., 2000, vol. 61, no. 19, pp. 12 964–12 969.
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