摘要
研究了碲锌镉衬底(111)晶面的不同极性对水平推舟液相外延生长碲镉汞薄膜的影响。实验结果显示,(111)A面碲锌镉衬底水平液相外延生长碲镉汞薄膜材料组分和厚度均与常规(111)B面碲锌镉衬底碲镉汞薄膜材料相当;碲镉汞母液在采用(111)A面、(111)B面衬底进行液相外延生长的碲镉汞薄膜上接触角分别为(50±2)°和(30±2)°,结合微观模型分析确认碲镉汞母液在碲镉汞薄膜(111)A面存在更大的表面张力;观察并讨论了(111)A面碲镉汞与(111)B面碲镉汞薄膜材料表面微观形貌的差别;实验获得的(111)A面碲镉汞薄膜XRD半峰宽为33.1 arcsec。首次报道了(111)晶面选择对母液残留的影响,研究结果表明,采用(111)A面碲锌镉衬底进行碲镉汞水平推舟液相外延生长,能够在不降低晶体质量的情况下,大幅减小薄膜表面母液残留。
碲镉汞是用于红外探测的一种极其重要的三元窄禁带半导体材料,具有一系列其他红外半导体材料无可比拟的优点,在红外遥感、红外夜视、红外测温、红外报警等国防军事及国民经济各个领域中发挥重要的作
碲镉汞晶体具有闪锌矿结构,对于闪锌矿结构晶体而言,(111)面是表面原子密度最高的晶面,从微观上看也是最平整的表面。通常情况下,碲镉汞液相外延都在(111)晶面的衬底上进行。闪锌矿结构晶体的(111)晶面由两层不同原子交叉堆积而成,由于闪锌矿结构不具有对称中心,因此(111)晶片的两个表面具有不同的极性,正极性的金属原子层表面被定义为(111)A表面,负极性的非金属原子层表面被定义为(111)B表
本文分别采用(111)A面和(111)B面碲锌镉衬底水平推舟外延生长了碲镉汞薄膜,对外延薄膜的光学性能、表面形貌、晶体质量等进行了表征,明确了碲锌镉衬底(111)A面与(111)B面在水平液相外延生长中的差别。本文首次报道了采用(111)A面碲锌镉衬底进行水平推舟液相外延生长可以大幅减少碲镉汞薄膜材料表面母液残留,并从碲锌镉(111)A面和(111)B面表面原子结构的差异出发,结合实验分析,认为碲镉汞生长母液在碲镉汞(111)A表面具有相对更大的表面张力,从而导致更少的残留母液。
本实验所采用的碲锌镉衬底为通过布里奇曼法生长的碲锌镉单晶材料切割而成,切割方向为(111)方向,衬底尺寸为25 mm×25 mm。在测试前,对表面进行机械抛光和化学机械抛光,去除表面损伤层,在生长前进一步使用0.5%的溴乙醇溶液腐蚀30 s以获得新鲜表面。外延生长采用水平推舟外延生长技术,母液配比为(Cd0.049Hg0.951)0.170Te0.830,目标薄膜组分为Hg0.80Cd0.20Te。外延生长开始温度为470 ℃,降温速率为0.2 ℃/min,生长时间为40 min。






图1 (a)CdZnTe(111)A面液相外延HgCdTe五点红外透过光谱;(b)相应五点的组分和厚度计算值;(c)三片CdZnTe(111)A面液相外延HgCdTe的组分和厚度;(d)CdZnTe(111)B面液相外延HgCdTe五点红外透过光谱;(e)相应五点的组分和厚度计算值;(f)三片CdZnTe(111)B面液相外延HgCdTe的组分和厚度
Fig. 1 (a) Infrared transmission spectra of five points on HgCdTe LPE material on CdZnTe (111) A surface, (b) Its corresponding calculative values of composition and thickness of the five points, (c) Composition and thickness of three HgCdTe samples on CdZnTe (111) A surface, (d) Infrared transmission spectra of five points on HgCdTe LPE material on CdZnTe (111) B surface, (e) Its corresponding calculative values of composition and thickness of the five points, (f) Composition and thickness of three HgCdTe samples on CdZnTe (111) B surface

图2 (a)CdZnTe(111)A面液相外延HgCdTe材料的宏观表面形貌照片;(b)CdZnTe(111)B面液相外延HgCdTe材料的宏观表面形貌照片
Fig. 2 (a) Photo of LPE HgCdTe sample on CdZnTe (111) A surface; (b) Photo of LPE HgCdTe sample on CdZnTe (111) B surface
通过侧向拍照手段对碲镉汞母液残留的轮廓曲线进行更进一步的分析处理,初步计算了碲镉汞熔体在(111)A面和(111)B面的接触角和表面张力。
γgl·cosθ+γsl =γsg , | (1) |






图3 (a)(c)(e)CdZnTe(111)A面液相外延HgCdTe材料母液残留正、侧向照片;(b)(d)(f)CdZnTe(111)B面液相外延HgCdTe材料母液残留正、侧向照片
Fig. 3 (a) (c) (e) Droplet photos of LPE HgCdTe film on CdZnTe (111) A surface; (b) (d) (f) Droplet photos of LPE HgCdTe film on CdZnTe (111) B surface
该现象的成因本质是闪锌矿结构晶体(111)A面与(111)B面表面化学结构不同。碲锌镉晶体与碲镉汞晶体均为闪锌矿结构,且具有非常接近的晶格常数。闪锌矿结构的碲镉汞晶体和碲锌镉晶体(111)B面最外层为Te原子层,其中每个Te原子具有1个悬挂键,次外层为金属原子层,其中每个Hg(或Cd)原子具有3个悬挂键;而(111)A面最外层为金属原子层,其中每个Hg(或Cd)原子仅具有一个悬挂键,次外层为Te原子层,其中每个Te原子具有3个悬挂

图4 水平推舟液相外延HgCdTe母液在碲镉汞(111)表面接触吸附示意图:(a)HgCdTe母液熔体位于(111)A面;(b)HgCdTe母液熔体位于(111)B面
Fig. 4 Schematic diagram of HgCdTe melt on HgCdTe film (111) surface in slider liquid phase epitaxal growth:(a) HgCdTe melt on HgCdTe (111) A surface,(b) HgCdTe melt on HgCdTe (111) B surface


图5 (a)CdZnTe(111)A面液相外延HgCdTe的表面显微形貌;(b)CdZnTe(111)B面液相外延HgCdTe的表面显微形貌
Fig. 5 (a) Surface morphology of LPE HgCdTe on CdZnTe (111) A surface; (b) Surface morphology of LPE HgCdTe on CdZnTe (111) B surface
HRXRD是分析晶体结晶质量的重要手段之一。在高分辨XRD测试中,我们可以通过双晶摇摆曲线的半峰宽(FWHM)来对晶体的质量进行表征。如果材料中存在晶格缺陷和位错,会导致测试到半峰宽展宽。为了研究衬底生长面极性对薄膜材料晶格质量的影响,我们使用高分辨XRD衍射仪对液相外延HgCdTe薄膜进行了ω-扫描测试。测试的结果显示,(111)A面液相外延HgCdTe薄膜与(111)B面液相外延HgCdTe薄膜的FWHM分别为33.1 arcsec和39.6 arcsec。对于碲镉汞材料(333)晶面FWHM文献一般报道水平为25~40 arcse

图6 (a)CdZnTe(111)A面液相外延HgCdTe材料XRD双晶摇摆曲线(b)CdZnTe(111)B面液相外延HgCdTe材料XRD双晶摇摆曲线
Fig. 6 (a) The ω-scans HRXRD rocking curve of LPE HgCdTe film grown on CdZnTe (111) A surface; (a) The ω-scans HRXRD rocking curve of LPE HgCdTe film grown on CdZnTe (111) B surface
本文采用水平推舟液相外延生长技术,在相同的工艺条件下,通过(111)A面和(111)B面碲锌镉衬底分别进行了碲镉汞外延生长实验,研究了不同极性的(111)晶面碲锌镉衬底对碲镉汞液相外延生长结果的影响。实验显示,碲锌镉(111)A面生长的碲镉汞薄膜组分、厚度、透过率等性能指标与碲锌镉(111)B面生长的碲镉汞薄膜相近。由于相较于(111)A面,(111)B面碲锌镉衬底外延生长的(111)B面碲镉汞薄膜表面Hg/Cd金属悬挂键更多,Te原子更容易在(111)B面上吸附,因此,碲镉汞母液在(111)A面上的表面张力更小,更容易在生长结束被扫出衬底,相同条件下,(111)A面上的母液残留面积更小。由于外延生长晶格输运机理有所区别,(111)A面碲锌镉衬底生长的碲镉汞薄膜生长台阶轮廓明显异于(111)B面,但其具体影响机制有待进一步研究。使用(111)A面和(111)B面外延生长的碲镉汞薄膜材料XRD半峰宽分别为33.1arcsec和39.6 arcsec,均具有较好的晶体质量。
本研究结果表明,采用(111)A面碲锌镉衬底外延生长的碲镉汞薄膜,晶体质量、表面形貌等均不劣于采用(111)B面碲锌镉衬底外延生长碲镉汞薄膜,(111)A面碲锌镉衬底还额外具有生长后母液易扫出的优势。因此可以认定,相较于通常使用的(111)B面碲锌镉衬底,使用(111)A面碲锌镉作为衬底材料是水平推舟液相外延碲镉汞薄膜更加优秀的技术途径。
References
Rogalski A. History of infrared detectors [J]. Opto-Electronics Review, 2012, 20(3): 279–308. [百度学术]
Chen Boliang, Li Xiangyang. Infrared imaging detectors for space applications [M]. Science Press, 2016. [百度学术]
陈伯良, 李向阳. 航天红外成像探测器. 科学出版社), 2016. [百度学术]
WenLei, Antoszewski J, Faraone O. Progress, challenges, and opportunities for HgCdTe infrared materials and detectors[J]. Applied Physics Reviews, 2015, 2(4): 041303. [百度学术]
Gravrand O, Destefanis G, Bisotto S, et al. Issues in HgCdTe Research and Expected Progress in Infrared Detector Fabrication[J]. Journal of Electronic Materials, 2013, 42(11): 3349-58. [百度学术]
Zeng Gehong. Development and Prospect of IR FPAs [J]. Infrared Technology, .曾戈虹. 红外焦平面器件的研制与展望 . 红外技术, 1995, 17(3):1-5. [百度学术]
Sun Quanzhi, Wei Yanfeng, Zhang Juan, et al. Effect of Lattice Mismatch on HgCdTe LPE Film Surface Morphology [J]. Journal of Electronic Materials, 2016, 45(9): 1-6. [百度学术]
Capper P, Garland J, Kasap S, et al. Mercury cadmium telluride : growth, properties, and applications [J]. Journal of Physics & Chemistry of Solids, 2010, 47(1): 65–68. [百度学术]
Granozzi G, Rizzi G A, Herman G S, et al. Polarity determination of the HgCdTe(111) surface by azimuthal X-ray photoelectron diffraction experiments [J]. Physica Scripta, 1990, 41(6):913. [百度学术]
Herman G S, Friedman D J, Tran T T, et al. X‐ray photoelectron diffraction from the HgCdTe(111) surface [J]. Journal of Vacuum Science & Technology B Microelectronics & Nanometer Structures, 1991, 235(3):1870-1873. [百度学术]
Takeuchi T, Kore-Eda T, Ebina A. Surface barriers formation mechanism of the chemically etched CdTe(111) polar surfaces and gold interfaces [J]. Applied Surface Science, 1996, s 100–101: 596-600. [百度学术]
Zha Gangqiang, Jie Wanqi, Tan Tingting, et al. The atomic and electronic structure of CdZnTe (1 1 1) A surface [J]. Chemical Physics Letters, 2006, 427: 196-200. [百度学术]
Kowalski B J, Orłowski B A, Ghijsen J. Oxide formation on the CdTe(111)A (1×1) surface [J]. Applied Surface Science, 2000, 166(1): 237-241. [百度学术]
Shih H D, Kinch M A, Aqariden F, et al. Development of high-operating-temperature infrared detectors with gold-doped Hg0.70Cd0.30Te [J]. Applied Physics Letters, 2004, 84(8):1263-1265. [百度学术]
Tennant W E, Arias J M, Bajaj J. HgCdTe at Teledyne [C]. SPIE Defense, Security, & Sensing. International Society for Optics and Photonics, 2009. [百度学术]
Qiu Guangyin, Zhang Chuanjie, Wei Yanfeng, et al. As-doped HgCdTe films grown by Te-rich LPE [J]. J. Infrared Millim. Waves .仇光寅, 张传杰, 魏彦锋,等. As掺杂碲镉汞富碲液相外延材料特性的研究 . 红外与毫米波学报, 2012, 31(1):15-20. [百度学术]
Wu Jun, Mao Xufeng, Wan Zhiyuan, et al. Improvement of Compositional Uniformity of HgCdTe Grown by LPE [J]. Infrared Technology.吴军, 毛旭峰, 万志远,等. 液相外延碲镉汞材料组分均匀性改善 . 红外技术, 2014, 36(12):973-975. [百度学术]
Song Shufang, Tian Zhen. Preparation study of p-type As doped HgCdTe material [J]. Laser and Infrared, 2018, 48(12):3.宋淑芳, 田震. 原位As掺杂p型碲镉汞薄膜的制备研究 . 激光与红外), 2018, 48(12):1500-1502. 10.3969/j.issn.1001-5078.2018.12.009 [百度学术]
Weiss E. Thirty years of HgCdTe technology in Israel [C]. Infrared Technology & Applications XXXV. International Society for Optics and Photonics, 2009. [百度学术]
Weiss E, Klin O, Benory E, et al. Substrate quality impact on the carrier concentration of undoped annealed HgCdTe LPE layers [J]. Journal of Electronic Materials, 2001, 30(6):756-761. [百度学术]
Benson J D, Varesi J B, Stoltz A J, et al. Surface structure of (111)A HgCdTe [J]. Journal of Electronic Materials, 2006, 35(6):1434-1442. [百度学术]
Yang Jianrong. Physics and technology of HgCdTe materials [M]. National Defense Industry Press, 2012. [百度学术]
杨建荣. 碲镉汞材料物理与技术. 国防工业出版社), 2012. [百度学术]
L.D.Landa, E.M.Lifshitz. Statistical Physics [M]. Higher Eduction Press, L.D.朗道, Е·М·栗弗席兹. 统计物理学, 高等教育出版社), 2012. [百度学术]
Shigenaka K, Sugiura L, Nakata F, et al. Effects of growth rate and mercury partial pressure on twin formation in HgCdTe (111) layers grown by metalorganic chemical vapor deposition[J]. Journal of Electronic Materials, 1993, 22(8):865-871. [百度学术]
Nishino H, Murakami S, Nishijima Y. Structure and Surface Properties of Metalorganic Vapor Phase Epitaxial CdTe and HgCdTe(111)B Layers Grown on Vicinal GaAs(100) Subatrates [J]. Japanese Journal of Applied Physics, 1999, 38(Part 1, No. 10): 5775-82. [百度学术]
Wang Jianli, Tang Gang,Wu X.S. , et al. The adsorption of O on (001) and (111) CdTe surfaces: A first-principles study [J]. Thin Solid Films, 2012, 520: 3960-3964. [百度学术]
Bai Xuxu, Jie Wanqi, Zha Gangqiang, et al. Adsorption of water molecules on the CdZnTe (111) B surface [J]. Chemical Physics Letters, 2010, 489(1-3): 103-106. [百度学术]
Radhakrishnan J K, Sitharaman S, Gupta S C. Surface morphology of Hg0.8Cd0.2Te epilayers grown by LPE using horizontal slider [J]. Applied Surface Science, 2003, 207: 33-9. [百度学术]
Mao Xufeng. Research on Preparation of HgCdTe films Crystal by liquid crystal phase epitaxy [D]. Yunnan University, 2013. [百度学术]
毛旭峰. 利用液相外延制备HgCdTe薄膜晶体的研究 . 云南大学), 2013. [百度学术]
Pelliciari B. Te-rich liquid-phase epitaxy of Hg1-x Cdx Te [J]. Progress in Crystal Growth and Characterization of Materials, 1994, 29(1-4): 1-39. [百度学术]
Castelein P, Baier N, Gravrand O, et al. Latest developments on p-on-n HgCdTe architectures at DEFIR[J]. Proceedings of the SPIE, 2014, 9070: 90702Y-1-14. [百度学术]
Sun Quanzhi, Sun Ruiyun, Wei Yanfeng,et al. Batch production technology of 50mm×50mm HgCdTe LPE materials with high performance [J]. J. Infrared Millim. Waves, 孙权志, 孙瑞赟, 魏彦锋,等. 50mm×50mm高性能HgCdTe液相外延材料的批生产技术 . 红外与毫米波学报, 2017, 36(1): 49-53. [百度学术]