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New defect states in irradiated p-type silicon
Volume 144, number 3
PHYSICS LETTERSA
26 February 1990
NEW DEFECT STATES IN IRRADIATED p-TYPE SILICON Kh.A. ABDULLIN, B.N. MUKASHEV, M.F. TAMENDAROV and T.B. TASHENOY Institute of High Energy Physics of theAcademy of Sciences ofthe Khazakh SSR, 480082 Alma-Ata 82, USSR Received 15 September 1989; accepted for publication 9 November 1989 Communicated by J.I. Budnick
DLTS measurements are used to detect two new defect states in irradiated p-type silicon. The amplitude and the rate of annealing of the E(0.39) state depend on the minority carrier injection level. It is supposed that the E(0.39) trap is a silicon interstitial related defect because the annealing of this state enhanced the concentration of interstitial carbon. The other new defect H (0.35) isidentified as a metastable precursor to the C 10, H (0.38) center. An energy barrier of 1 cv separates the MH(0.35) state from the stable C10, configuration.
Recently several impurity interstitial related defects were identified by using the deep level transient spectroscopy (DLTS) method [1,2]. In this report the observations of the self-interstitial related state as well as the metastable precursor ofthe well known interstitial carbon—interstitial oxygen (C101, K-center) defect [3] are presented. For the preparation of all samples silicon wafers were used, cut from Czochralski-grown (CG) or float zone (FZ) crystals doped by boron, aluminium or gallium with a resistivity of about 5—10 L~cm. A Schottky barrier diode or diffused junction was bombarded at room temperature by 4.7 MeY a-partides. For the determination of the deep level properties, capacitance transient spectroscopy with thirdorder filtering was employed [4]. The a-particle irradiation introduced the following defects: Hi (0.20, divacancy, VV), H2(0.29, C1), H4(0.38, C101), E(0.27, unidentified) [2,5], and two new defectvalues states are E(0.39) H3(0.35). The errors of these about and ±0.01 eV. The minority carrier trap of E (0.39) appears in all the irradiated samples irrespective of the kind of acceptor impurity in CG and FZ silicon. Therefore this state does not include an impurity atom, it should be an intrinsic defect. The amplitude and the rate of annealing of the E(0.39) defect depend on the minority carrier injection level as well as on the concentration of carbon and oxygen impurities. Fig. 1 shows 198
H2
2
..
I
E2
TEMPERATURE (K 4cm 3)silicon following irradiation by a-particles, 0(4.7 MeV) = 5 x 10 Fig. 21.DLTSspectraofFZ,boron-doped(p=6x10’ cm at 0°C.First (1) and fourth (2) temperature scan in the range 100—250 K with minority carrier injection.
typical transient capacitance spectra of an FZ boron doped sample under the following conditions: reverse bias 8 V, injection current density 0.1 A/cm2, after irradiation by a-particles (5 x lOb cm 2) at 0 C. Curves 1 and 2 display the first and fourth ternperature scan in the range 100—250 K. Forward bias
Volume 144, number 3
PHYSICS LETTERSA
1
injection of the diodes greatly enhances the annealing of this trap. This result clearly indicates strong dependence øf the rate of annealing on the minority
— —~
_________________
-á
I
~
carrier injection. The annealing of E (0.39) increases the concentration of the H2(0.29, C1) state. Hence one may conclude that the E(0.39) intrinsic defect is connected with the silicon interstial-related center. The defect is annealed at 60°Cand during a few days at room temperature. The dependence of the an nealing of E(O.39) on the minority carrier injection level indicates that the defect is positively charged and captures an electron easily. However this defect is not observed in EPR experiments [61, which is why it should be in the charge state. During the trap filling pulse the Si~ ions easily capture electrons: Si~+ + e Si ~ due to the Coulombic attraction for electron capture. The charge transfer can take place also due to the thermal transition of the electron to the E (0.39) state at 60°C.Therefore the Si~state anneals by capturing an electron through the charge state mechanism [71.The charge-state dependence of migration energies has been established for isolated vacancies [81 and vacancy—V group impurity atoms [9,10]. It is reasonable to suppose that the E(0.39) state is(3s2 connected with the self-interstitial donor state Si~ 3p)/Si~(3s2). The annealing of the H2(O.29, C 1) state increases the concentration of the H4(0.38, C~O1)defect. Using third-order filtering allows us to resolve the new defect state H3, see fig. 2. Note that the usual firstorder filtering DLTS spectrometer gave one broad
26 February 1990
I d <
:
i___________________ -____________________
Ak2
,
atb.uni.ts
Fig. 3. The dependence of the amplitudes (AH) of the H3 (1) and the sum H3+H4 (2) peaks of DLTS spectra on the amplitude (AH2) ofthe H2 center during thermal annealing
H4 peak with a low temperature shoulder. Fig. 3 shows the dependence of the amplitudes of the H3 and H4 peaks on the amplitude of the H2 center. It is clear that during the annealing the H2 trap completely transforms into the sum of the H3 + H4 defects. Initially the amplitudes ofthe H3 and H4 states grow approximately similarly with annealing of the H2 defect. After that the H3 completely turns into the H4. The activation energy of this process isEvi1.0 12 eV and the frequency factor is 6x l0 dently the H3 center is a metastable precursor at the ~
ground state ofthe CO, defect. It is the intermediate configuration between the C, (H2, 0.29) and C101 (H4, 0.38) states. In summary, we have observed two new defect states in irradiated silicon. The first is tentatively 2~donor state and the secconnected with the Si~ /Si ond is a metastable configuration of the C 10, ground state. It is clear that further detailed studies are reespecially for the E(0.39) defect. quired for the identification of these defect states,
d -J
z Co
References
CO -J
‘150
200
TEMPERATURE, K
3) silicon irradiation a-particles at(p=6X 20°C. l0’~cm It is the inFig. 2. following DLTS spectra of CZ,byboron-doped termediate state of the transition of the H2 center to H3+H4 duringthermal annealing.
[1] J.L. Benton, M.T. Asom, R. Sauer and L.C. Kimerling, in: Materials Research Society Proceedings, Vol. 104. Defects in electronic materials, eds. M. Stavola, S.J. Pearton and G. 86. Davies (Materials Research Society, Pittsburgh, 1988) p. [2] L.C. Kimerling, M.T. Asom, J.L. Benton, P.J. Drevinsky and C.E. Caefer, in: Materials science forum, Vols. 38—41, Part 3(1989) pp. 141—150.
199
Volume 144, number 3
PHYSICS LETTERS A
[3] J.M. Trombetta and G.D. Watkins, AppI. Phys. Lett. 51 (1987) 1103. [4]C.R. Cromwell and S. Alipanashi, Solid State Electron. 24 (1981) 25. [5] V.1. Gubskay, P.V. Kuchinski and V.M. Lomaco, Fiz. Tekn. Poluprovodn. 20 (1986) 1055. [6]R.D.Harris and G.D. Watkins, in: Proc. l3thlnt. Conf. on Def. semiconductors (1985) p.799.
200
26 February 1990
[7] J.R. Troxell, A.P. Chatterjee and G.D. Watkins, Phys. Rev. B 19(1979) 5336. [8]G.D. Watkins, Inst. Phys. Conf. Ser. 23 (1975) 1 [9] L.C. Kimerling, H.M. DeAngelis and J.W. Diebold, Solid State Commun. 16 (1975) 171. [10] A.O. Evwaraye, J. AppI. Phys. 48 (1977) 734.
PHYSICS LETTERSA
26 February 1990
NEW DEFECT STATES IN IRRADIATED p-TYPE SILICON Kh.A. ABDULLIN, B.N. MUKASHEV, M.F. TAMENDAROV and T.B. TASHENOY Institute of High Energy Physics of theAcademy of Sciences ofthe Khazakh SSR, 480082 Alma-Ata 82, USSR Received 15 September 1989; accepted for publication 9 November 1989 Communicated by J.I. Budnick
DLTS measurements are used to detect two new defect states in irradiated p-type silicon. The amplitude and the rate of annealing of the E(0.39) state depend on the minority carrier injection level. It is supposed that the E(0.39) trap is a silicon interstitial related defect because the annealing of this state enhanced the concentration of interstitial carbon. The other new defect H (0.35) isidentified as a metastable precursor to the C 10, H (0.38) center. An energy barrier of 1 cv separates the MH(0.35) state from the stable C10, configuration.
Recently several impurity interstitial related defects were identified by using the deep level transient spectroscopy (DLTS) method [1,2]. In this report the observations of the self-interstitial related state as well as the metastable precursor ofthe well known interstitial carbon—interstitial oxygen (C101, K-center) defect [3] are presented. For the preparation of all samples silicon wafers were used, cut from Czochralski-grown (CG) or float zone (FZ) crystals doped by boron, aluminium or gallium with a resistivity of about 5—10 L~cm. A Schottky barrier diode or diffused junction was bombarded at room temperature by 4.7 MeY a-partides. For the determination of the deep level properties, capacitance transient spectroscopy with thirdorder filtering was employed [4]. The a-particle irradiation introduced the following defects: Hi (0.20, divacancy, VV), H2(0.29, C1), H4(0.38, C101), E(0.27, unidentified) [2,5], and two new defectvalues states are E(0.39) H3(0.35). The errors of these about and ±0.01 eV. The minority carrier trap of E (0.39) appears in all the irradiated samples irrespective of the kind of acceptor impurity in CG and FZ silicon. Therefore this state does not include an impurity atom, it should be an intrinsic defect. The amplitude and the rate of annealing of the E(0.39) defect depend on the minority carrier injection level as well as on the concentration of carbon and oxygen impurities. Fig. 1 shows 198
H2
2
..
I
E2
TEMPERATURE (K 4cm 3)silicon following irradiation by a-particles, 0(4.7 MeV) = 5 x 10 Fig. 21.DLTSspectraofFZ,boron-doped(p=6x10’ cm at 0°C.First (1) and fourth (2) temperature scan in the range 100—250 K with minority carrier injection.
typical transient capacitance spectra of an FZ boron doped sample under the following conditions: reverse bias 8 V, injection current density 0.1 A/cm2, after irradiation by a-particles (5 x lOb cm 2) at 0 C. Curves 1 and 2 display the first and fourth ternperature scan in the range 100—250 K. Forward bias
Volume 144, number 3
PHYSICS LETTERSA
1
injection of the diodes greatly enhances the annealing of this trap. This result clearly indicates strong dependence øf the rate of annealing on the minority
— —~
_________________
-á
I
~
carrier injection. The annealing of E (0.39) increases the concentration of the H2(0.29, C1) state. Hence one may conclude that the E(0.39) intrinsic defect is connected with the silicon interstial-related center. The defect is annealed at 60°Cand during a few days at room temperature. The dependence of the an nealing of E(O.39) on the minority carrier injection level indicates that the defect is positively charged and captures an electron easily. However this defect is not observed in EPR experiments [61, which is why it should be in the charge state. During the trap filling pulse the Si~ ions easily capture electrons: Si~+ + e Si ~ due to the Coulombic attraction for electron capture. The charge transfer can take place also due to the thermal transition of the electron to the E (0.39) state at 60°C.Therefore the Si~state anneals by capturing an electron through the charge state mechanism [71.The charge-state dependence of migration energies has been established for isolated vacancies [81 and vacancy—V group impurity atoms [9,10]. It is reasonable to suppose that the E(0.39) state is(3s2 connected with the self-interstitial donor state Si~ 3p)/Si~(3s2). The annealing of the H2(O.29, C 1) state increases the concentration of the H4(0.38, C~O1)defect. Using third-order filtering allows us to resolve the new defect state H3, see fig. 2. Note that the usual firstorder filtering DLTS spectrometer gave one broad
26 February 1990
I d <
:
i___________________ -____________________
Ak2
,
atb.uni.ts
Fig. 3. The dependence of the amplitudes (AH) of the H3 (1) and the sum H3+H4 (2) peaks of DLTS spectra on the amplitude (AH2) ofthe H2 center during thermal annealing
H4 peak with a low temperature shoulder. Fig. 3 shows the dependence of the amplitudes of the H3 and H4 peaks on the amplitude of the H2 center. It is clear that during the annealing the H2 trap completely transforms into the sum of the H3 + H4 defects. Initially the amplitudes ofthe H3 and H4 states grow approximately similarly with annealing of the H2 defect. After that the H3 completely turns into the H4. The activation energy of this process isEvi1.0 12 eV and the frequency factor is 6x l0 dently the H3 center is a metastable precursor at the ~
ground state ofthe CO, defect. It is the intermediate configuration between the C, (H2, 0.29) and C101 (H4, 0.38) states. In summary, we have observed two new defect states in irradiated silicon. The first is tentatively 2~donor state and the secconnected with the Si~ /Si ond is a metastable configuration of the C 10, ground state. It is clear that further detailed studies are reespecially for the E(0.39) defect. quired for the identification of these defect states,
d -J
z Co
References
CO -J
‘150
200
TEMPERATURE, K
3) silicon irradiation a-particles at(p=6X 20°C. l0’~cm It is the inFig. 2. following DLTS spectra of CZ,byboron-doped termediate state of the transition of the H2 center to H3+H4 duringthermal annealing.
[1] J.L. Benton, M.T. Asom, R. Sauer and L.C. Kimerling, in: Materials Research Society Proceedings, Vol. 104. Defects in electronic materials, eds. M. Stavola, S.J. Pearton and G. 86. Davies (Materials Research Society, Pittsburgh, 1988) p. [2] L.C. Kimerling, M.T. Asom, J.L. Benton, P.J. Drevinsky and C.E. Caefer, in: Materials science forum, Vols. 38—41, Part 3(1989) pp. 141—150.
199
Volume 144, number 3
PHYSICS LETTERS A
[3] J.M. Trombetta and G.D. Watkins, AppI. Phys. Lett. 51 (1987) 1103. [4]C.R. Cromwell and S. Alipanashi, Solid State Electron. 24 (1981) 25. [5] V.1. Gubskay, P.V. Kuchinski and V.M. Lomaco, Fiz. Tekn. Poluprovodn. 20 (1986) 1055. [6]R.D.Harris and G.D. Watkins, in: Proc. l3thlnt. Conf. on Def. semiconductors (1985) p.799.
200
26 February 1990
[7] J.R. Troxell, A.P. Chatterjee and G.D. Watkins, Phys. Rev. B 19(1979) 5336. [8]G.D. Watkins, Inst. Phys. Conf. Ser. 23 (1975) 1 [9] L.C. Kimerling, H.M. DeAngelis and J.W. Diebold, Solid State Commun. 16 (1975) 171. [10] A.O. Evwaraye, J. AppI. Phys. 48 (1977) 734.