硫钝化GaP半导体表面性质的研究
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摘要
近年来，Ⅲ-V族化合物半导体已在电子和光电子器件中广泛地应用。以Ⅲ-V族化合物为材料场效应晶体管(MESFET)是手机的一关键元件。然而，表面态的存在降低了晶体管的性能。因此，发展表面钝化技术工作是很重要的。在这方面，已有许多关于用S钝化处理的报道，它们可以有效地降低半导体的表面态。
在本文研究了GaP(111)单晶、外延片在90±2℃的CH3CSNH2溶液中不同钝化工艺条件对表面性质的影响。用X光电子能谱仪(XPS)和扫描电子显微镜(SEM)分析在不同钝化时间下GaP的表面形貌、微结构、化学组分及电子能谱的变化，同时我们还借助光致荧光谱(PL)来分析钝化的效果。
XPS测量结果表明，钝化后在GaP表面生成了Ga和P的硫化物，Ga3d、Ga2p和P2p的芯能级ESCA峰与未钝化样品相比较都向高结合能端移动，其化学位移值与有关文献报道较一致。钝化样品表面经Ar+离子溅射(电压为5kV，电流密度为100μA／cm2)后，Ga3d、Ga2p和P2p的芯能级峰向低结合能端移动。从这些元素谱峰的变化，特别是O1s芯能级峰的强度变化可判断分析出GaP表面
的氧化物基本被去除。因而，在GaP表面形成一层薄的S覆盖层。
由SEM观测表面形貌可看出，经CH厂SNH。溶液钝化20min的GaP表面与
其它钝化处理时间比较，其表面比较均匀、平整，微结构呈连续密集分布，这说
明湿法钝化需要一定的时间；从CH。CSNH。分解出来的S’与Ga原子的键合是
一个吸热过程，须在一定的温度下进行。结合XPS和 SEM的测量分析结果，
探讨了CH。CSNH。钝化GaP表面的可能机理。
我们报道了 n七aP外延片门 11）面钝化后光致荧光测量的结果，经 CH厂SNH。
溶液处理的n－GaP样品的荧光强度有显著提高，尤其是钝化25min的样品。光
致荧光强度的增强标志着GaP表面复合速率的降低，表面缺陷、态密度的减小，
同时也说明在GaP表面上形成S的钝化层。
In recent years III-V compound semiconductor have been practically applied to electronic and optoelectronic devices. Many kinds of 1II-V metal semiconductor field-effect transistors (MESFET's) are used as a key device in portable telephones. However, surfaces states degrade the performance of MESFET's. Therefore, it is of great importance to develop process technology for surface passivation. In this aspect, there have been reported that a surface treatment with sulfur is effective in reducing the surface state density.
In this paper, the GaP wafer surfaces were passivated with CH3CSNH2 solution of certain concentration at 90 ?2癈 temperature. The effect of passivation for different time on the surface structure, morphology and electronic features was investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). We also investigated the photoluminescence (PL) characteristics of GaP after it was treated
The XPS measurement results indicate that the gallium sulfide and phosphorus sulfide have been formed on the surface during the passivation. It is found that the XPS peaks of the Ga3d, Ga2p and P2p are shifted to higher binding energy compared with the untreated sample and the results are similar to other foreign correlative work. The passivated surfaces were further sputtered by Ar+ ions for 8min under the condition of voltage 5kV, current density 100(jA/cm2. It shows that the Ga3d, Ga2p and P2p peaks are located at the lower binding energies compared with unsputtered samples. The XPS analysis results also reveal that the surface oxide compound of GaP has removed basically, especially from the strength change of Ols core level. Hence it implied that a thin S overlayer has been formed on the GaP surface, which can prevent the oxidation from environment. It possesses a good chemical stability.
The SEM observation appeared that the treatment time by CH3CSNH2 solution for 20min is determined to obtain a uniform passivation film on the GaP surface compared with other treatment time, this means that the wet chemical reactions were completed in a certain interval of time when GaP wafer was dipped in the CH2CSNH3 solution. The chemical reaction between the Ga atoms of GaP surface and the S2" ions dissociated from the CH3CSNH2 solution has taken place under the condition of certain temperature. From the measurement results of XPS and SEM, the possible passivated mechanism of CH3CSNH2 solution to GaP surfaces is also discussed.
The PL measurement results reveal that the photoluminescent intensity of treatment sample is improved greatly, especially the treatment time is 25min. it indicate the reduction of surface combination velocity of GaP, resulting in the reduction of surface defect states due to the formation of sulfur passivation films.
在本文研究了GaP(111)单晶、外延片在90±2℃的CH3CSNH2溶液中不同钝化工艺条件对表面性质的影响。用X光电子能谱仪(XPS)和扫描电子显微镜(SEM)分析在不同钝化时间下GaP的表面形貌、微结构、化学组分及电子能谱的变化，同时我们还借助光致荧光谱(PL)来分析钝化的效果。
XPS测量结果表明，钝化后在GaP表面生成了Ga和P的硫化物，Ga3d、Ga2p和P2p的芯能级ESCA峰与未钝化样品相比较都向高结合能端移动，其化学位移值与有关文献报道较一致。钝化样品表面经Ar+离子溅射(电压为5kV，电流密度为100μA／cm2)后，Ga3d、Ga2p和P2p的芯能级峰向低结合能端移动。从这些元素谱峰的变化，特别是O1s芯能级峰的强度变化可判断分析出GaP表面
的氧化物基本被去除。因而，在GaP表面形成一层薄的S覆盖层。
由SEM观测表面形貌可看出，经CH厂SNH。溶液钝化20min的GaP表面与
其它钝化处理时间比较，其表面比较均匀、平整，微结构呈连续密集分布，这说
明湿法钝化需要一定的时间；从CH。CSNH。分解出来的S’与Ga原子的键合是
一个吸热过程，须在一定的温度下进行。结合XPS和 SEM的测量分析结果，
探讨了CH。CSNH。钝化GaP表面的可能机理。
我们报道了 n七aP外延片门 11）面钝化后光致荧光测量的结果，经 CH厂SNH。
溶液处理的n－GaP样品的荧光强度有显著提高，尤其是钝化25min的样品。光
致荧光强度的增强标志着GaP表面复合速率的降低，表面缺陷、态密度的减小，
同时也说明在GaP表面上形成S的钝化层。
In recent years III-V compound semiconductor have been practically applied to electronic and optoelectronic devices. Many kinds of 1II-V metal semiconductor field-effect transistors (MESFET's) are used as a key device in portable telephones. However, surfaces states degrade the performance of MESFET's. Therefore, it is of great importance to develop process technology for surface passivation. In this aspect, there have been reported that a surface treatment with sulfur is effective in reducing the surface state density.
In this paper, the GaP wafer surfaces were passivated with CH3CSNH2 solution of certain concentration at 90 ?2癈 temperature. The effect of passivation for different time on the surface structure, morphology and electronic features was investigated using scanning electron microscopy (SEM) and X-ray photoelectron spectroscopy (XPS). We also investigated the photoluminescence (PL) characteristics of GaP after it was treated
The XPS measurement results indicate that the gallium sulfide and phosphorus sulfide have been formed on the surface during the passivation. It is found that the XPS peaks of the Ga3d, Ga2p and P2p are shifted to higher binding energy compared with the untreated sample and the results are similar to other foreign correlative work. The passivated surfaces were further sputtered by Ar+ ions for 8min under the condition of voltage 5kV, current density 100(jA/cm2. It shows that the Ga3d, Ga2p and P2p peaks are located at the lower binding energies compared with unsputtered samples. The XPS analysis results also reveal that the surface oxide compound of GaP has removed basically, especially from the strength change of Ols core level. Hence it implied that a thin S overlayer has been formed on the GaP surface, which can prevent the oxidation from environment. It possesses a good chemical stability.
The SEM observation appeared that the treatment time by CH3CSNH2 solution for 20min is determined to obtain a uniform passivation film on the GaP surface compared with other treatment time, this means that the wet chemical reactions were completed in a certain interval of time when GaP wafer was dipped in the CH2CSNH3 solution. The chemical reaction between the Ga atoms of GaP surface and the S2" ions dissociated from the CH3CSNH2 solution has taken place under the condition of certain temperature. From the measurement results of XPS and SEM, the possible passivated mechanism of CH3CSNH2 solution to GaP surfaces is also discussed.
The PL measurement results reveal that the photoluminescent intensity of treatment sample is improved greatly, especially the treatment time is 25min. it indicate the reduction of surface combination velocity of GaP, resulting in the reduction of surface defect states due to the formation of sulfur passivation films.
引文
[1] Spicer W E, Chye P W, Skeath P R, et al., "New and unified model for Schottky barrier and III-V insulator interface states formation" J. Vac. Sci. Technol., 16(1979) , 1422．
[2] Zahn DRT, Kampen TU, Hohenecker S, Braun W, "GaAs serface passivation by ultra-high vacuum deposition of chalcogen atoms", Vacuum, 57(2000) ,139．
[3] Rudolph R, Pettenkofer C, Klein A, Jaegermann W, "Chemical passivation of Si(111) capped by a thin GaSe layer",167(2000) , 122．
[4] McGovern IT, Korbbel A, Leslie A, Dudzik E, et al., "X-ray standing wave study of wet-etch sulphur-treated InP(100) surface", Applied surface science, 166(2000) , 196．
[5] Lebedev MV, Aono M, "Valence band photoemission, band bending, and ionization energy of GaAs(100) treated in alcoholic sulfide solution", Journal of appled physics, 87(2000) , 289．
[6] Fukuda Y, Suzuki Y, Sanada N, Shimomura M, Masuda S, "(NH4) 2S.x-treated InAs(001) surface studied by x-ray photoelectron spectrosxopy and low-energy electron diffraction", Physical Review B, 56(1997) , 1084．
[7] Beaudry R, Watkins SP, Xu XG, Yeo P, "Photoreflectance study of phosphorus passivation of GaAs (001) ", Journal of applied physics, 87(2000) , 7838．
[8] Kim JW, Kang MG, Park HH, "Investigation on the surface characteristics of GaAs after sulfuric-vapor", Thin Solid Films, 356(1999) , 423．
[9] Kim JW, Kang MG, Park HH, "Distribution of S in (NH4) 2S-X-treated GaAs surface", Journal of the Korean physical society, 35(1999) , 152．
[10] Choy WH, Kwork RWM, So BKL, Hui GKC, et al. "Surface roughness and oxide contents of gas-phase and solution-phase polysulfide passivation of III-V surface", 17(1999) , 93．
[11] Miller EA, Richmond GL, "Photocorrosion of n-GaAs and passivation by Na2S: A comparison of the (100) , (110) , and (111) B face", 101(1997) , 2669．
[12] Bessolov VN, Lebedev MV, "Chalcogenide passivation of III-V semiconductor surfaces", Semiconductors, 32(1998) , 1141．
[13] Han IK, Kim EK, Lee JL, et al. "Srability of sulfur-treated InP surface studied by photoluminescence and x-ray photoelectron spectroscopy", Journal of applied physics, 81(1997) , 6986．
[14] Sandroff C J, Nortenburg R N, Bischoff J C, et al., "Dramatic senhancement in the gain of a GaAs/AlGaAs heterostructure bipolar transistor by surface chemical passivation", Appl. Phys. Lett., 51(1987) , 33．
[15] Y. Mada, K. Wada, and Y. Wada, "Passivaton of (NH4) 2-S-treated GaAs surface with a As2S3 film", Appl. Phys. Lett., 61(1992) , 2993．
[16] Y. Mada, and K. Wada, "Passavition of an n-type GaAs surface with an As2S2 film"Appl. Phys., Lett. 66(1995) , 733．
[17] Y. Mada, and K. Wada, "Passavition of an n-type InP surface with an As2S3 film"J. Appl. Phys. 83 (1998) , 2025．
[18] L. M. Terman, "An investigation of surface states at a silicon/silicon oxide interface employing metal-oxide-silicon diodes", Solid-State Electronics,5(1962) , 285．
[19] Islam ABMO, Tambo T and Tatsuyama C, "Passivation of GaAs surface by GaS" ,Vacuum, 59(2000) , 894．
[20] Sun Jx, Seo Dj, " Chemical bonding and electronic properties of SeS2-treated GaAs(100) ", J. Appl., 85(1999) , 969．
[21] Nozu S, Matsuda K, Sugino T, "Charaterization of GaAs surface treated with remote PH3 plasma" J. Appl. Phys., 38(1999) , 295．
[22] Tsai CD, Lee CT, "Passivation mechanism analysis of sulfur-passivated InGaP surface using X-ray photoelectron", J. Appl. Phys., 87(2000) , 4230．
[23] Martinez GL and Curiel, "Surface recombination and sulfide passivation of GaN", J. Electronic Mterials, 29(2000) , 325．
[24] Eftekhari G, "Thermal stability of indium tin oxide/n-GaAs heterostures with
and without sulfur passivation", Physica status solidi a-applied research, 178(2000), 709.
[25] Kang MG, Kim JW, Park HH, "Amelioration of the interfacial properties in Au/GaAs Schottky contact using sulfidationg and hydrogenation",Japanese journal of applied physics part 1-regular papers short notes & review papers, 39(2000), 7003.
[26] Datta S, Gokhale MR, Shah AP, Arora BM, Kumar S,"Temperature dependence id surface photovoltage of bulk semiconductors and the effect of surface passivation",Applied physics letters, 77(2000), 4383.
[27] 袁泽亮、丁训民等，“中性(NH_4)_2S_2溶液钝化GaAs(100)表面的研究”物理学报，47(1998)，68．
[28] 陆尔东、张发培、余小江等，“GaAs表面硫化学钝化，CH_3CSNH_2处理新探”，物理学报，46(1997)，2022．
[29] Sugarara H, Oshima M, Oigawa H el al., "Chemistry of S/GaAs and metal/S/GaAs system",J. Vac. Sci. Technol.,1993, A11 (1):52-57.
[30] 林秀华，徐富春，江炳熙，“用CH_3CSNH_2钝化GaP表面特性的研究”，发光学报，21(2000)，115．
[31] Nordling C, Sterman,"J. Physics Handbook",Henan Sci. &Tech. Press, Zhengzhou, (1986)56.
[32] Sandroff C J, Hedge M S, Chiang C C,"Electronic passivation of GaAs surfaces through the formation of arsenic-sulfur bonds",J. Vac. Sci. Technol.,B7(1989), 841.
[33] B.A.Cowans, Z.Dardas, M.S.Carpenter et al., "X-ray photoelectron scectroscopy of ammonium sulfide treated GaAs(100)",Appl. Phys. Lett.,54(1989), 365.
[34] X.Y. Hou, W. Z. Cai, Z. Q. He et al., "Electrochemical sulfur passivation of GaAs",Appl. Phys. Lett.,60(1992), 2252.
[35] Z.S. Li, W. Z. Cai, R. Z. Su et al.,"S2C12 treatment: A new sulfur passivation method of GaAs serface", Appl. Phys. Lett.,64(1994), 3425.
[36] 王建祺、吴文辉、冯大明，“电子能谱引论”，北京：国防工业出版社，1992，P．24．
[37] H. Sugahara, M. Oshima, H. Oigawa et al., "Synchrotron radiation photemission analysisfor(NH4)2Sx-treated GaAs",J. Appl. Phys.,69(1991), 4349.
[38] C.J. Spindt, D, Liu, K. Miyano et al., "Vacuum ultraviolet photoelectron spectroscopy of (NH4)2S-treated GaAs (100) surface",Appl. Phys. Lett.,55(1989), 861.
[39] Wagner C D, Riggs W M, Davis L E, et al., "HANDBOOK X-RAY PHOTOELECTRON SPECTROSCOPY",Perkin-Elmer Corporation Physics Electronics Division, Eden Prairie Minnesota, (1978), 56-57.
[40] Xu Chunfang, Lu Xuekun, "Advance of sulfide treated InSb(111) surface",Semicond Technol.,10(1991), 12.
[41] 陆家和、陈长彦等，“表面分析技术”，电子工业出版社，(1987)，249．
[42] D.R. Wight, J. Phys. D: Appl. Phys.,10(1977)4, 431.
[2] Zahn DRT, Kampen TU, Hohenecker S, Braun W, "GaAs serface passivation by ultra-high vacuum deposition of chalcogen atoms", Vacuum, 57(2000) ,139．
[3] Rudolph R, Pettenkofer C, Klein A, Jaegermann W, "Chemical passivation of Si(111) capped by a thin GaSe layer",167(2000) , 122．
[4] McGovern IT, Korbbel A, Leslie A, Dudzik E, et al., "X-ray standing wave study of wet-etch sulphur-treated InP(100) surface", Applied surface science, 166(2000) , 196．
[5] Lebedev MV, Aono M, "Valence band photoemission, band bending, and ionization energy of GaAs(100) treated in alcoholic sulfide solution", Journal of appled physics, 87(2000) , 289．
[6] Fukuda Y, Suzuki Y, Sanada N, Shimomura M, Masuda S, "(NH4) 2S.x-treated InAs(001) surface studied by x-ray photoelectron spectrosxopy and low-energy electron diffraction", Physical Review B, 56(1997) , 1084．
[7] Beaudry R, Watkins SP, Xu XG, Yeo P, "Photoreflectance study of phosphorus passivation of GaAs (001) ", Journal of applied physics, 87(2000) , 7838．
[8] Kim JW, Kang MG, Park HH, "Investigation on the surface characteristics of GaAs after sulfuric-vapor", Thin Solid Films, 356(1999) , 423．
[9] Kim JW, Kang MG, Park HH, "Distribution of S in (NH4) 2S-X-treated GaAs surface", Journal of the Korean physical society, 35(1999) , 152．
[10] Choy WH, Kwork RWM, So BKL, Hui GKC, et al. "Surface roughness and oxide contents of gas-phase and solution-phase polysulfide passivation of III-V surface", 17(1999) , 93．
[11] Miller EA, Richmond GL, "Photocorrosion of n-GaAs and passivation by Na2S: A comparison of the (100) , (110) , and (111) B face", 101(1997) , 2669．
[12] Bessolov VN, Lebedev MV, "Chalcogenide passivation of III-V semiconductor surfaces", Semiconductors, 32(1998) , 1141．
[13] Han IK, Kim EK, Lee JL, et al. "Srability of sulfur-treated InP surface studied by photoluminescence and x-ray photoelectron spectroscopy", Journal of applied physics, 81(1997) , 6986．
[14] Sandroff C J, Nortenburg R N, Bischoff J C, et al., "Dramatic senhancement in the gain of a GaAs/AlGaAs heterostructure bipolar transistor by surface chemical passivation", Appl. Phys. Lett., 51(1987) , 33．
[15] Y. Mada, K. Wada, and Y. Wada, "Passivaton of (NH4) 2-S-treated GaAs surface with a As2S3 film", Appl. Phys. Lett., 61(1992) , 2993．
[16] Y. Mada, and K. Wada, "Passavition of an n-type GaAs surface with an As2S2 film"Appl. Phys., Lett. 66(1995) , 733．
[17] Y. Mada, and K. Wada, "Passavition of an n-type InP surface with an As2S3 film"J. Appl. Phys. 83 (1998) , 2025．
[18] L. M. Terman, "An investigation of surface states at a silicon/silicon oxide interface employing metal-oxide-silicon diodes", Solid-State Electronics,5(1962) , 285．
[19] Islam ABMO, Tambo T and Tatsuyama C, "Passivation of GaAs surface by GaS" ,Vacuum, 59(2000) , 894．
[20] Sun Jx, Seo Dj, " Chemical bonding and electronic properties of SeS2-treated GaAs(100) ", J. Appl., 85(1999) , 969．
[21] Nozu S, Matsuda K, Sugino T, "Charaterization of GaAs surface treated with remote PH3 plasma" J. Appl. Phys., 38(1999) , 295．
[22] Tsai CD, Lee CT, "Passivation mechanism analysis of sulfur-passivated InGaP surface using X-ray photoelectron", J. Appl. Phys., 87(2000) , 4230．
[23] Martinez GL and Curiel, "Surface recombination and sulfide passivation of GaN", J. Electronic Mterials, 29(2000) , 325．
[24] Eftekhari G, "Thermal stability of indium tin oxide/n-GaAs heterostures with
and without sulfur passivation", Physica status solidi a-applied research, 178(2000), 709.
[25] Kang MG, Kim JW, Park HH, "Amelioration of the interfacial properties in Au/GaAs Schottky contact using sulfidationg and hydrogenation",Japanese journal of applied physics part 1-regular papers short notes & review papers, 39(2000), 7003.
[26] Datta S, Gokhale MR, Shah AP, Arora BM, Kumar S,"Temperature dependence id surface photovoltage of bulk semiconductors and the effect of surface passivation",Applied physics letters, 77(2000), 4383.
[27] 袁泽亮、丁训民等，“中性(NH_4)_2S_2溶液钝化GaAs(100)表面的研究”物理学报，47(1998)，68．
[28] 陆尔东、张发培、余小江等，“GaAs表面硫化学钝化，CH_3CSNH_2处理新探”，物理学报，46(1997)，2022．
[29] Sugarara H, Oshima M, Oigawa H el al., "Chemistry of S/GaAs and metal/S/GaAs system",J. Vac. Sci. Technol.,1993, A11 (1):52-57.
[30] 林秀华，徐富春，江炳熙，“用CH_3CSNH_2钝化GaP表面特性的研究”，发光学报，21(2000)，115．
[31] Nordling C, Sterman,"J. Physics Handbook",Henan Sci. &Tech. Press, Zhengzhou, (1986)56.
[32] Sandroff C J, Hedge M S, Chiang C C,"Electronic passivation of GaAs surfaces through the formation of arsenic-sulfur bonds",J. Vac. Sci. Technol.,B7(1989), 841.
[33] B.A.Cowans, Z.Dardas, M.S.Carpenter et al., "X-ray photoelectron scectroscopy of ammonium sulfide treated GaAs(100)",Appl. Phys. Lett.,54(1989), 365.
[34] X.Y. Hou, W. Z. Cai, Z. Q. He et al., "Electrochemical sulfur passivation of GaAs",Appl. Phys. Lett.,60(1992), 2252.
[35] Z.S. Li, W. Z. Cai, R. Z. Su et al.,"S2C12 treatment: A new sulfur passivation method of GaAs serface", Appl. Phys. Lett.,64(1994), 3425.
[36] 王建祺、吴文辉、冯大明，“电子能谱引论”，北京：国防工业出版社，1992，P．24．
[37] H. Sugahara, M. Oshima, H. Oigawa et al., "Synchrotron radiation photemission analysisfor(NH4)2Sx-treated GaAs",J. Appl. Phys.,69(1991), 4349.
[38] C.J. Spindt, D, Liu, K. Miyano et al., "Vacuum ultraviolet photoelectron spectroscopy of (NH4)2S-treated GaAs (100) surface",Appl. Phys. Lett.,55(1989), 861.
[39] Wagner C D, Riggs W M, Davis L E, et al., "HANDBOOK X-RAY PHOTOELECTRON SPECTROSCOPY",Perkin-Elmer Corporation Physics Electronics Division, Eden Prairie Minnesota, (1978), 56-57.
[40] Xu Chunfang, Lu Xuekun, "Advance of sulfide treated InSb(111) surface",Semicond Technol.,10(1991), 12.
[41] 陆家和、陈长彦等，“表面分析技术”，电子工业出版社，(1987)，249．
[42] D.R. Wight, J. Phys. D: Appl. Phys.,10(1977)4, 431.