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1. V.E. Lashkaryov Institute of Semiconductor Physics of the National Academy of Sciences of Ukraine, Kyiv 03028, Ukraine
2. B.I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, Minsk 220072, Belarus
3. Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8011, Japan
Received: December 06, 2011 / Accepted: December 27, 2011 / Published: April 25, 2012.
Abstract: The mechanisms of the laser-stimulated diffusion of indium in CdTe have been studied. The structures of a thin In film on the CdTe substrate were irradiated by nanosecond pulses of ruby, KrF excimer and Nd:YAG lasers. It is established that the dominanting mechanism of In diffusion in CdTe at solid-phase (before CdTe melting) doping is baro-diffusion. The diffusion coefficient and average drift velocity of indium are determined. The temperature dynamics and kinetics of laser-induced phase transitions are studied by numerical simulation on the basis of Stefan problem.
Key words: Nanosecond laser irradiation, diffusion, doping, In/CdTe.
1 Introduction??
The effect of fast diffusion caused by high mobility of atoms in crystals at pulsed laser irradiation (PLI), allows to realize the solid- and liquid- phase doping of the submicron layers of the semiconductor crystals by pulsed irradiation of the metal, semiconductor system[1-15]. This method of the doping of semiconductor crystal surface layers is very efficient for forming of the sharp p-n- junctions at a small depth [1-6, 9-13]. In the case of a In thin film deposited on the CdTe substrate the laser irradiation can be used for creation of the X-ray and gamma-ray detectors with a low level of noise and improved spectrometric parameters [1-5].
At the same time the mechanisms of the fast diffusion in metal, semiconductor structures at PLI are not clearly understood. The elucidation of these mechanisms is important for the forecast and controlled changes of physical, electric, photo-electric properties of semiconductor structures and devices of the different assignment, especially, of the detectors of the ionizing radiation on the CdTe basis.
The clarification of dominanting mechanisms of the fast diffusion and also the study of the melting thresholds of the In film and CdTe are also necessary for the determination of the optimum regimes of the nanosecond laser-stimulated doping of the CdTe by indium. The complexity of the description of the diffusion (mass-transfer) in these systems at nanosecond irradiation is caused by substantial deviation from thermodynamic equilibrium, a high rate and a flowing simultaneously of different physical processes. In particular, they are phase transformations, generation of elastic and shock waves [8, 16], generation of the considerable temperature gradients and thermo-elastic stresses.
In this connection, the object of the work is the determination of the dominating mechanisms and basic regularities of the fast diffusion of indium in CdTe at PLI of the thin-film In/CdTe system. We also carried out the modelling of the laser heating and melting of these structures.
4. Conclusions
The features and mechanisms of diffusion of doping element (indium) in CdTe under nanosecond laser irradiation of the system In film-CdTe substrate for doping the CdTe subsurface layer and forming the p-njunction have been considered and analysed.
It is ascertain that the dominant diffusion mechanism at the laser solid-phase (up to the melting threshold of
Acknowledgments
The work was supported by Fundamental Researches State Fund of Ukraine, Project No F41.1/032 and Belarusian Republican Foundation for Fundamental Research, Project No F11K-098.
References
[1] A. Nakamura, M. Niraula, K. Asano, T. Aoki, Y. Nakanishi, Y. Hatanaka, n-type and p-tupe doping techniques for CdTe crystal using excimer laser annealing, Proceedings of JICAST, 6th Joint International Conference, China, Dec. 15-16 (2001) 164-167.
[2] V.A. Gnatyuk, T. Aoki, Y. Hatanaka, Laser-induced shock wave stimulated doping of CdTe crystals, Applied Physics Letters 88 (2006) 242111.
[3] V.A. Gnatyuk, T. Aoki, M. Niraula, Y. Hatanaka, Influence of laser irradiation and laser-induced In doping on the photoluminescence of CdTe crystals, Semiconductor Science and Technology 18 (2003) 560-565.
[4] M. Niraula, A. Nakamura, T. Aoki, Y. Tomita, Y. Hatanaka, A new fabrication technique of CdTe strip detectors for gamma-ray imaging and spectroscopy, Physica Status Solidi B 229 (2002) 1103-1107.
[5] A. Togami, Y. Ishida, T. Aoki, J. Temmyo, Y. Hatanaka. Evaluation of properties of various type CdTe hard X-ray detectors, Proc. SPIE 5922 (2005) 592210.
[6] V.А. Gnatyuk, T. Aoki, O.I. Vlasenko, S.N. Levytskyi, Y. Hatanaka, C.P. Lambropoulos, Features of characteristics and stability of CdTe nuclear radiation detectors fabricated by laser doping technique, Hard X-Ray, Gamma-Ray and Neutron Detector Physics X. Proceedings of SPIE 7079(2008) 70790G-1-9.
[7] N.K. Zelenina, O.A. Matveev, Laser implantation of impurities in cadmium telluride crystals, Technical Physics Letters 6 (1998) 411-413.
[8] N.N. Berchenko, V.S. Yakovyna, Y.N. Nikiforov, I.I. Izhnin, K.R. Kurbanov, Laser-induced shock waves processing of II-VI solid solutions interface, Journal of Alloys and Compounds 371 (2004) 86-88.
[9] G. Kerrien, T. Sarnet, D. Débarre, J. Boulmer, M. Hernandez, C. Laviron, M.N. Semeria, Gas immersion laser doping (GILD) for ultra-shallow junction formation, Thin Solid Films Proceedings of Symposium 1 (2004) 106-109.
[10] X. Tong, L. Chen, Y. Wang, Effect of Si-substrate heating during laser-induced B-doping, Applied Physics A 59(1994) 189-191.
[11] A. Ogane, K. Hirata, K. Horiuchi, Y. Nishihara, Yu. Takahashi, A. Kitiyanan, T. Fuyuki, Laser-doping technique using ultraviolet laser for shallow doping in crystalline silicon solar cell fabrication, Japanese Journal of Applied Physics 48 (2009) 071201.
[12] V.A. Pilipovich, G.D. Ivlev, Y.F. Morgun, N.V. Nechaev,
V.I. Osinskii, A.Y. Peshko, Formation of p-n junctions in gallium arsenide by laser irradiation, Journal of Applied Spectroscopy 22 (1975) 324-328.
[13] V.V. Zhidkov, G.D. Ivlev, Y.F. Morgun, Action of pulsed laser radiation on zinc, gallium arsenide system, Izvestiya AN BSSR. ser. fiz.-mat, nauk. 4 (1987) 89-93.
[14] V.P. Voronkov, G.A. Gurchenok, Impurity diffusion in semiconductors at laser annealing, Semiconductors 24(1990) 1831-1834.
[15] G.A. Sukach, Laser induced shift of a p-n junction boundary in direct-gap GaAsP structures, Semiconductors 6 (1997) 645-648.
[16] A. Baidullaeva, A.I. Vlasenko, B.L. Gorkovenko, A.V. Lomovtsev, P.E. Mozol, Variation in the defect structure of p-CdTe single crystals at the passage of the laser shock wave, Semiconductors 4 (2000) 429-432.
[17] J. Manning, Diffusion Kinetics for Atoms in Crystals, Van Nostrand, Princeton, 1968.
[18] M.E. Gurevich, A.F. Zhuravlev, L.N. Larikov, V.G. Novitski?, A.E. Pogorelov, Research of the directed transfer of atoms in metals under action of the laser radiation, Metallofizika 3 (1981) 108-112.
[19] D.S. Gertsriken, V.F. Mazanko, V.M. Tyshkevich, V.M. Fal’chenko, Mass Transfer in Metals at Low Temperatures under Conditions of External Stresses, Institute of Metal. Physics, Kiev, 1999.
[20] M.E. Gurevich, L.N. Larikov, V.F. Mazanko, A.E. Pogorelov, V.M. Fal’chenko, Influence of the laser radiation on the mobility of atoms of iron, Fizika i Khimiya Obrabotki Materialov 2 (1977) 7-9.
[21] V.B. Fiks, Ion Conductivity in Metals and Semiconductors(Electrotransfer), Nauka, Moscow, 1969.
[22] R. Triboulet, P. Siffert, CdTe and related compounds; physics, defects, hetero- and nano-structures, crystal growth, Surfaces and Applications, Elsevier Ltd. 2010.
[23] E. Gatskevich, P. P?ikryl, G. Ivlev, Modelling laser-induced phase transformations in semiconductors, Mathematics and Computer in Simulation 76 (2007) 65-72.
[24] H. Landolt, R. B?rnstein, Numerical Data and Functional Relationships in Sciences and Technology, Springer-Verlag, Berlin, 1982.
[25] O. Madelung, Semiconductors, Data Handbook, 3rd ed, Springer, 2004.
[26] A.N. Bekrenev, G.N. Epshte?n, Postdeformation Processes of High-Speed Loading, Metallurgiya, Moscow, 1992.
[27] V.A. Putilin, A.M. Shterenberg, A.V. Kamashev, A.I. Krestelev, The dynamics of the interstitial atoms in the laser-induced flat shock wave, Vestnik Samarskogo Gos. Tekh. Univ., Ser. Fiz.-Mat. 9 (2000) 190-191.
[28] Y.Y. Meshkov, D.S. Gertsriken, V.F. Mazanko, To the question about mass-transfer mechanism in the metals under pulse load conditions, Metallofizika i Noveishie Tekhnologii 4 (1996) 52-52.
[29] A.E. Pogorelov, K.P. Ryaboshapka, A.F. Zhuravlyov, Mass transfer mechanism in real crystals by pulsed laser irradiation, Journal of Applied Physics 92 (2002) 5766-5771.
[30] A.N. Valyaev, A.D. Pogrebnyak, V.I. Lavrent’ev, S.N. Volkov, S.V. Plotnikov, Influence of the shock wave pressure gradient in α-Fe irradiated by a high-power ion beam on the occurence of a microhardness maximum at large depths, Technical Physics Letters 24 (1998) 102-104.
[31] V.P. Veleshchuk, A. Ba?dullaeva, A.I. Vlasenko, V.A. Gnatyuk, B.K. Dauletmuratov, S.N. Levitskii, et al., Mass transfer of indium in the In-CdTe structure under nanosecond laser irradiation, Physics of the Solid State 52(2010) 469-476.
[32] M.N. Libenson, M.N. Nikitin, About diffusion of atoms of the film in substrate under the action of laser radiation, Fiz. Khim. Obrab. Mater. 1 (1973) 9-14.
[33] P. Fochuk, O. Panchuk, P. Feychuk, L. Shcherbak, A. Savitskyi, O. Parfenyuk, et al., Indium dopant behaviour in CdTe single crystals, Nuclear Instruments and Methods in Physics Research A 458 (2001) 104-112.
2. B.I. Stepanov Institute of Physics of the National Academy of Sciences of Belarus, Minsk 220072, Belarus
3. Research Institute of Electronics, Shizuoka University, Hamamatsu 432-8011, Japan
Received: December 06, 2011 / Accepted: December 27, 2011 / Published: April 25, 2012.
Abstract: The mechanisms of the laser-stimulated diffusion of indium in CdTe have been studied. The structures of a thin In film on the CdTe substrate were irradiated by nanosecond pulses of ruby, KrF excimer and Nd:YAG lasers. It is established that the dominanting mechanism of In diffusion in CdTe at solid-phase (before CdTe melting) doping is baro-diffusion. The diffusion coefficient and average drift velocity of indium are determined. The temperature dynamics and kinetics of laser-induced phase transitions are studied by numerical simulation on the basis of Stefan problem.
Key words: Nanosecond laser irradiation, diffusion, doping, In/CdTe.
1 Introduction??
The effect of fast diffusion caused by high mobility of atoms in crystals at pulsed laser irradiation (PLI), allows to realize the solid- and liquid- phase doping of the submicron layers of the semiconductor crystals by pulsed irradiation of the metal, semiconductor system[1-15]. This method of the doping of semiconductor crystal surface layers is very efficient for forming of the sharp p-n- junctions at a small depth [1-6, 9-13]. In the case of a In thin film deposited on the CdTe substrate the laser irradiation can be used for creation of the X-ray and gamma-ray detectors with a low level of noise and improved spectrometric parameters [1-5].
At the same time the mechanisms of the fast diffusion in metal, semiconductor structures at PLI are not clearly understood. The elucidation of these mechanisms is important for the forecast and controlled changes of physical, electric, photo-electric properties of semiconductor structures and devices of the different assignment, especially, of the detectors of the ionizing radiation on the CdTe basis.
The clarification of dominanting mechanisms of the fast diffusion and also the study of the melting thresholds of the In film and CdTe are also necessary for the determination of the optimum regimes of the nanosecond laser-stimulated doping of the CdTe by indium. The complexity of the description of the diffusion (mass-transfer) in these systems at nanosecond irradiation is caused by substantial deviation from thermodynamic equilibrium, a high rate and a flowing simultaneously of different physical processes. In particular, they are phase transformations, generation of elastic and shock waves [8, 16], generation of the considerable temperature gradients and thermo-elastic stresses.
In this connection, the object of the work is the determination of the dominating mechanisms and basic regularities of the fast diffusion of indium in CdTe at PLI of the thin-film In/CdTe system. We also carried out the modelling of the laser heating and melting of these structures.
4. Conclusions
The features and mechanisms of diffusion of doping element (indium) in CdTe under nanosecond laser irradiation of the system In film-CdTe substrate for doping the CdTe subsurface layer and forming the p-njunction have been considered and analysed.
It is ascertain that the dominant diffusion mechanism at the laser solid-phase (up to the melting threshold of
Acknowledgments
The work was supported by Fundamental Researches State Fund of Ukraine, Project No F41.1/032 and Belarusian Republican Foundation for Fundamental Research, Project No F11K-098.
References
[1] A. Nakamura, M. Niraula, K. Asano, T. Aoki, Y. Nakanishi, Y. Hatanaka, n-type and p-tupe doping techniques for CdTe crystal using excimer laser annealing, Proceedings of JICAST, 6th Joint International Conference, China, Dec. 15-16 (2001) 164-167.
[2] V.A. Gnatyuk, T. Aoki, Y. Hatanaka, Laser-induced shock wave stimulated doping of CdTe crystals, Applied Physics Letters 88 (2006) 242111.
[3] V.A. Gnatyuk, T. Aoki, M. Niraula, Y. Hatanaka, Influence of laser irradiation and laser-induced In doping on the photoluminescence of CdTe crystals, Semiconductor Science and Technology 18 (2003) 560-565.
[4] M. Niraula, A. Nakamura, T. Aoki, Y. Tomita, Y. Hatanaka, A new fabrication technique of CdTe strip detectors for gamma-ray imaging and spectroscopy, Physica Status Solidi B 229 (2002) 1103-1107.
[5] A. Togami, Y. Ishida, T. Aoki, J. Temmyo, Y. Hatanaka. Evaluation of properties of various type CdTe hard X-ray detectors, Proc. SPIE 5922 (2005) 592210.
[6] V.А. Gnatyuk, T. Aoki, O.I. Vlasenko, S.N. Levytskyi, Y. Hatanaka, C.P. Lambropoulos, Features of characteristics and stability of CdTe nuclear radiation detectors fabricated by laser doping technique, Hard X-Ray, Gamma-Ray and Neutron Detector Physics X. Proceedings of SPIE 7079(2008) 70790G-1-9.
[7] N.K. Zelenina, O.A. Matveev, Laser implantation of impurities in cadmium telluride crystals, Technical Physics Letters 6 (1998) 411-413.
[8] N.N. Berchenko, V.S. Yakovyna, Y.N. Nikiforov, I.I. Izhnin, K.R. Kurbanov, Laser-induced shock waves processing of II-VI solid solutions interface, Journal of Alloys and Compounds 371 (2004) 86-88.
[9] G. Kerrien, T. Sarnet, D. Débarre, J. Boulmer, M. Hernandez, C. Laviron, M.N. Semeria, Gas immersion laser doping (GILD) for ultra-shallow junction formation, Thin Solid Films Proceedings of Symposium 1 (2004) 106-109.
[10] X. Tong, L. Chen, Y. Wang, Effect of Si-substrate heating during laser-induced B-doping, Applied Physics A 59(1994) 189-191.
[11] A. Ogane, K. Hirata, K. Horiuchi, Y. Nishihara, Yu. Takahashi, A. Kitiyanan, T. Fuyuki, Laser-doping technique using ultraviolet laser for shallow doping in crystalline silicon solar cell fabrication, Japanese Journal of Applied Physics 48 (2009) 071201.
[12] V.A. Pilipovich, G.D. Ivlev, Y.F. Morgun, N.V. Nechaev,
V.I. Osinskii, A.Y. Peshko, Formation of p-n junctions in gallium arsenide by laser irradiation, Journal of Applied Spectroscopy 22 (1975) 324-328.
[13] V.V. Zhidkov, G.D. Ivlev, Y.F. Morgun, Action of pulsed laser radiation on zinc, gallium arsenide system, Izvestiya AN BSSR. ser. fiz.-mat, nauk. 4 (1987) 89-93.
[14] V.P. Voronkov, G.A. Gurchenok, Impurity diffusion in semiconductors at laser annealing, Semiconductors 24(1990) 1831-1834.
[15] G.A. Sukach, Laser induced shift of a p-n junction boundary in direct-gap GaAsP structures, Semiconductors 6 (1997) 645-648.
[16] A. Baidullaeva, A.I. Vlasenko, B.L. Gorkovenko, A.V. Lomovtsev, P.E. Mozol, Variation in the defect structure of p-CdTe single crystals at the passage of the laser shock wave, Semiconductors 4 (2000) 429-432.
[17] J. Manning, Diffusion Kinetics for Atoms in Crystals, Van Nostrand, Princeton, 1968.
[18] M.E. Gurevich, A.F. Zhuravlev, L.N. Larikov, V.G. Novitski?, A.E. Pogorelov, Research of the directed transfer of atoms in metals under action of the laser radiation, Metallofizika 3 (1981) 108-112.
[19] D.S. Gertsriken, V.F. Mazanko, V.M. Tyshkevich, V.M. Fal’chenko, Mass Transfer in Metals at Low Temperatures under Conditions of External Stresses, Institute of Metal. Physics, Kiev, 1999.
[20] M.E. Gurevich, L.N. Larikov, V.F. Mazanko, A.E. Pogorelov, V.M. Fal’chenko, Influence of the laser radiation on the mobility of atoms of iron, Fizika i Khimiya Obrabotki Materialov 2 (1977) 7-9.
[21] V.B. Fiks, Ion Conductivity in Metals and Semiconductors(Electrotransfer), Nauka, Moscow, 1969.
[22] R. Triboulet, P. Siffert, CdTe and related compounds; physics, defects, hetero- and nano-structures, crystal growth, Surfaces and Applications, Elsevier Ltd. 2010.
[23] E. Gatskevich, P. P?ikryl, G. Ivlev, Modelling laser-induced phase transformations in semiconductors, Mathematics and Computer in Simulation 76 (2007) 65-72.
[24] H. Landolt, R. B?rnstein, Numerical Data and Functional Relationships in Sciences and Technology, Springer-Verlag, Berlin, 1982.
[25] O. Madelung, Semiconductors, Data Handbook, 3rd ed, Springer, 2004.
[26] A.N. Bekrenev, G.N. Epshte?n, Postdeformation Processes of High-Speed Loading, Metallurgiya, Moscow, 1992.
[27] V.A. Putilin, A.M. Shterenberg, A.V. Kamashev, A.I. Krestelev, The dynamics of the interstitial atoms in the laser-induced flat shock wave, Vestnik Samarskogo Gos. Tekh. Univ., Ser. Fiz.-Mat. 9 (2000) 190-191.
[28] Y.Y. Meshkov, D.S. Gertsriken, V.F. Mazanko, To the question about mass-transfer mechanism in the metals under pulse load conditions, Metallofizika i Noveishie Tekhnologii 4 (1996) 52-52.
[29] A.E. Pogorelov, K.P. Ryaboshapka, A.F. Zhuravlyov, Mass transfer mechanism in real crystals by pulsed laser irradiation, Journal of Applied Physics 92 (2002) 5766-5771.
[30] A.N. Valyaev, A.D. Pogrebnyak, V.I. Lavrent’ev, S.N. Volkov, S.V. Plotnikov, Influence of the shock wave pressure gradient in α-Fe irradiated by a high-power ion beam on the occurence of a microhardness maximum at large depths, Technical Physics Letters 24 (1998) 102-104.
[31] V.P. Veleshchuk, A. Ba?dullaeva, A.I. Vlasenko, V.A. Gnatyuk, B.K. Dauletmuratov, S.N. Levitskii, et al., Mass transfer of indium in the In-CdTe structure under nanosecond laser irradiation, Physics of the Solid State 52(2010) 469-476.
[32] M.N. Libenson, M.N. Nikitin, About diffusion of atoms of the film in substrate under the action of laser radiation, Fiz. Khim. Obrab. Mater. 1 (1973) 9-14.
[33] P. Fochuk, O. Panchuk, P. Feychuk, L. Shcherbak, A. Savitskyi, O. Parfenyuk, et al., Indium dopant behaviour in CdTe single crystals, Nuclear Instruments and Methods in Physics Research A 458 (2001) 104-112.