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Far-infrared photoconductivity spectroscopies of GaAs thin film at electric fields
454
ABSTRACTS A new kind of N-O thermal donors (NOTD} were generated when the N-doped Ct-Si samples were annealed in 300 - 550°C. NOTDs are quite similar to the thermal donors (TD) in Cz-Si, but NOTDs are monovalent donor with leve!s the sa~e as those of neutral thermal donors TD °. No new donors is formed for samples annea!ed in 600 - ~O0°C, This means that the presence of nitrogen in Cz-Si suppress the formation of new thermal donors(ND).
FAR-INFRARED PHOTOCON D UCTIVITY SPECTROSCOPIES OF GaAs FILM AT ELECTRIC FIELDS
THIN
Zhonghui Chcn S.C. Shen National Laboratory for Infrared Physics, Shanghai Institute o f Teclmical Physics, Academia Sinica,200083, China We mcasured far infrared photoconductivity spectroscopies o f Sidoped GaAs thin film at different bias as well as dark current-voltage characteristics at 4.2K. Our experinacnts show that the intensity of the peak I S ~ 2 P increases with the field supe,'linearly below the critical field of 5V/cm, rapidly drop to zero above it. In addition, the currentvoltage characteristics show a S-shaped negative resistance at critical field o f 5.5V/cm, which is larger than value determined by spectroscopics. This difference originate from the fact that far infrared radiation changes the generationrecombination between donor and conduction band. On the basis of noaequilibrium phase transition theory, we conclude that far infrared radiation, as well as the external field and temperature, can induce and control the nonequilibrium phase transition of Si-dopcd GaAs. By considering the variation o f intensity o f IS--*2P transition with field and the I-V characteristics, we find that the ionization probability o f 2P state increase with external electric field below 5V/cm. In addition to plaotothcrnml ionization, the impact ionization and field-induced tunneling process may play an important role at higher field in far infrared photoconductivity o f Si-doped GaAs.
Oxv~en Comnlexin2 with Group !! Impurities in Silicon
S.E. Daly, J.D. Ciunpion, E. McGlyml, M.O. I leury School of Physical Sciences, Dublin City Utfiversity, Collins Avenue, Dublin 9, Ireland. /M.C. do Canno ,'uld M.II. Nazart~, I~elmrtimento de Fisica, Llniversid',Klede Aveiro, 3800 Aveiro, Portugal. Czochralski-grown (CZ) silicon crystals contain high concentrations of oxygen incorporated during the growth process. The presence of the oxygen is of
Vol. 93, No. 5 considerable technical significance since it affects both the mechanical and electrical properties of silicon wafers. As a result, the interactions of oxygen impurities with defects and other impurities in silicon, and the aggregation of oxygen during thermal annealing, have been studied extensively [ 1]. The majority of the group II e l e m e n t s are incorporated in silicon as aeceptors or as poorly specified defect complexes, with magnesium alone having a well-established donor behaviour [2]. We report the results of a comprehensive photoluminescence (PL) study at liquid helimn temperatures of CZ-silicon doped with the group II impurities Be, Zn and Cd. For Be, a strong zerophonon transition is observed at 1138.17(5) meV with a series of sharp high energy local mode phonon replicas. For Zn, two separate PL spectra are observed with zero-phonon line energies at 1129.82(5) meV and 1090.68(5) meV. In the case of Cd, a sharp line is observed at 980.26 (5) meV. Uniaxial stress measurements show that in all cases the defects are of axial symmetry. The absence of these defects in FZ silicon samples provides strong circumstantial evidence for the involvement of oxygen. The data are interpreted in the context of shallow impurity levels and the implications of the data for the control of oxygen behaviour in silicon are discussed. References
[1] 2037 [2] 462
V.V. Voronkov, Semicond. Sci. Technol. 8 (1993) and references therein LT. Ho and A.K. Ramadas, Phys. Rev. BS, (1972)
Annihilation Studies of Oxygen-related (4700C) Thermal Donor Centers in CZ-Si W.G6tz 1, G.Pensl2, W.Zulehner3, R.Addinall4, and R.C.Newman4 1SolidState ElectronicsLab, Stanford University Stanford, CA 94305, USA. 21nstitutfor AngewandtePhysik,91058 Edangen, Germany 3Wacker Chemitronic,84489 Burghausen,Germany 4InterdisciplinaryResearchCentrefor Semiconductor Materials,LondonSW7 2BZ, UnitedKingdom Thermal Donors (TDs) are generated in oxygen rich Czochralski-grown silicon (CZ-Si) at temperatures around 450°C. They form a family of shallow double donors (TDx) which differ slightly in ground state binding energies in both the neutral charge state (TDx0) and the positive charge state (TDx+). In this study the annihilation kinetics of individual TDx centers grown at 470°C is investigated in CZ-Si ([Oi]=l.3x1018cm-3), using two different sets (A,B) of samples which differ in the TD starting concentrations [TDtot] start, but not in the total oxygen content. ['l'Dtot] start of set A samples, is equal to 5x1015cm -3, while [TDtodstart of set B samples corresponds to 2xl0Y3cm-3. Pairs of samples (A, B) are exposed to various heat treatments in the temperature range from 4800C to 700°C in a Rapid Thermal Annealing (RIA) system. Changes in the concentration of individual TDx centers and in the interstitial oxygen due to the heat treatments conducted for l s up to 20h are monitored by FTIR absorption measurements. We demonstrate that individual TDx centers
ABSTRACTS A new kind of N-O thermal donors (NOTD} were generated when the N-doped Ct-Si samples were annealed in 300 - 550°C. NOTDs are quite similar to the thermal donors (TD) in Cz-Si, but NOTDs are monovalent donor with leve!s the sa~e as those of neutral thermal donors TD °. No new donors is formed for samples annea!ed in 600 - ~O0°C, This means that the presence of nitrogen in Cz-Si suppress the formation of new thermal donors(ND).
FAR-INFRARED PHOTOCON D UCTIVITY SPECTROSCOPIES OF GaAs FILM AT ELECTRIC FIELDS
THIN
Zhonghui Chcn S.C. Shen National Laboratory for Infrared Physics, Shanghai Institute o f Teclmical Physics, Academia Sinica,200083, China We mcasured far infrared photoconductivity spectroscopies o f Sidoped GaAs thin film at different bias as well as dark current-voltage characteristics at 4.2K. Our experinacnts show that the intensity of the peak I S ~ 2 P increases with the field supe,'linearly below the critical field of 5V/cm, rapidly drop to zero above it. In addition, the currentvoltage characteristics show a S-shaped negative resistance at critical field o f 5.5V/cm, which is larger than value determined by spectroscopics. This difference originate from the fact that far infrared radiation changes the generationrecombination between donor and conduction band. On the basis of noaequilibrium phase transition theory, we conclude that far infrared radiation, as well as the external field and temperature, can induce and control the nonequilibrium phase transition of Si-dopcd GaAs. By considering the variation o f intensity o f IS--*2P transition with field and the I-V characteristics, we find that the ionization probability o f 2P state increase with external electric field below 5V/cm. In addition to plaotothcrnml ionization, the impact ionization and field-induced tunneling process may play an important role at higher field in far infrared photoconductivity o f Si-doped GaAs.
Oxv~en Comnlexin2 with Group !! Impurities in Silicon
S.E. Daly, J.D. Ciunpion, E. McGlyml, M.O. I leury School of Physical Sciences, Dublin City Utfiversity, Collins Avenue, Dublin 9, Ireland. /M.C. do Canno ,'uld M.II. Nazart~, I~elmrtimento de Fisica, Llniversid',Klede Aveiro, 3800 Aveiro, Portugal. Czochralski-grown (CZ) silicon crystals contain high concentrations of oxygen incorporated during the growth process. The presence of the oxygen is of
Vol. 93, No. 5 considerable technical significance since it affects both the mechanical and electrical properties of silicon wafers. As a result, the interactions of oxygen impurities with defects and other impurities in silicon, and the aggregation of oxygen during thermal annealing, have been studied extensively [ 1]. The majority of the group II e l e m e n t s are incorporated in silicon as aeceptors or as poorly specified defect complexes, with magnesium alone having a well-established donor behaviour [2]. We report the results of a comprehensive photoluminescence (PL) study at liquid helimn temperatures of CZ-silicon doped with the group II impurities Be, Zn and Cd. For Be, a strong zerophonon transition is observed at 1138.17(5) meV with a series of sharp high energy local mode phonon replicas. For Zn, two separate PL spectra are observed with zero-phonon line energies at 1129.82(5) meV and 1090.68(5) meV. In the case of Cd, a sharp line is observed at 980.26 (5) meV. Uniaxial stress measurements show that in all cases the defects are of axial symmetry. The absence of these defects in FZ silicon samples provides strong circumstantial evidence for the involvement of oxygen. The data are interpreted in the context of shallow impurity levels and the implications of the data for the control of oxygen behaviour in silicon are discussed. References
[1] 2037 [2] 462
V.V. Voronkov, Semicond. Sci. Technol. 8 (1993) and references therein LT. Ho and A.K. Ramadas, Phys. Rev. BS, (1972)
Annihilation Studies of Oxygen-related (4700C) Thermal Donor Centers in CZ-Si W.G6tz 1, G.Pensl2, W.Zulehner3, R.Addinall4, and R.C.Newman4 1SolidState ElectronicsLab, Stanford University Stanford, CA 94305, USA. 21nstitutfor AngewandtePhysik,91058 Edangen, Germany 3Wacker Chemitronic,84489 Burghausen,Germany 4InterdisciplinaryResearchCentrefor Semiconductor Materials,LondonSW7 2BZ, UnitedKingdom Thermal Donors (TDs) are generated in oxygen rich Czochralski-grown silicon (CZ-Si) at temperatures around 450°C. They form a family of shallow double donors (TDx) which differ slightly in ground state binding energies in both the neutral charge state (TDx0) and the positive charge state (TDx+). In this study the annihilation kinetics of individual TDx centers grown at 470°C is investigated in CZ-Si ([Oi]=l.3x1018cm-3), using two different sets (A,B) of samples which differ in the TD starting concentrations [TDtot] start, but not in the total oxygen content. ['l'Dtot] start of set A samples, is equal to 5x1015cm -3, while [TDtodstart of set B samples corresponds to 2xl0Y3cm-3. Pairs of samples (A, B) are exposed to various heat treatments in the temperature range from 4800C to 700°C in a Rapid Thermal Annealing (RIA) system. Changes in the concentration of individual TDx centers and in the interstitial oxygen due to the heat treatments conducted for l s up to 20h are monitored by FTIR absorption measurements. We demonstrate that individual TDx centers