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材料的载流子浓度和迁移率是影响器件性能的关键因素, 变温Hall测试结果证明杂质掺杂AlGaN中的载流子浓度和迁移率随温度 降低而减小.然而极化诱导掺杂的载流子浓度和迁移率不受温度变化的影响.以准绝缘 的GaN体材料作为衬底, 在组分分层渐变的AlGaN中实现的极化诱导掺杂浓度 仅仅在1017 cm-3数量级甚至更低. 本研究采用载流子浓度为1016 cm-3量级的非有意n型掺杂GaN模板为衬底, 用极化诱导掺杂技术在分子束外延生长的AlGaN薄膜材料中实现了高 达1020 cm-3 量级的超高电子浓度. 准绝缘的体材GaN半导体作衬底时, 只有表面自由电子作为极化掺杂源, 而非有意掺杂的GaN模板衬底除了提供表面自由电子外,还能为极化电场 提供更多的自由电子源, 从而实现超高载流子浓度的n型掺杂.Carrier concentration and mobility of materials are key factors affecting device performance. Hall tests at different temperatures demonstrate that the carrier concentration and mobility in impurity-doped AlGaN decrease with temperature decreasing. However, carrier concentration and mobility obtained by polarization-induced doping are independent of temperature. Using quasi-insulating GaN as substrate, the electron concentration obtained in the linearly graded AlGaN film through impurity-doping is only 10-17 cm-3 or less. In this study, using unintentional impurity doped (n-type, 10-16 cm-3) GaN template, graded AlGaN film is grown by molecular beam epitaxial, in which polarization induced ultra-high electron concentration is up to 1020 cm-3 in graded AlGaN film without using any dopant. Using quasi-insulating GaN as substrate, only the surface of the free electrons serves as polarization dopant, while unintentionally doped GaN template is used as a substrate, in addition to free electrons on surface/interface, it is also reasonable to surmise more negative charges attracted by polarization electric field to be the source of polarization doping, in the unintentional doped GaN template, thereby achieving an ultra-high carrier concentration via polarization induced n-type doping.
[1] Chang J Y, Liou B T, Lin H W, Shih Y H, Chang S H, Kuo Y K 2011 Opt. Lett. 36 3500
[2] Gonschorek M, Carlin J F, Feltin E, Py M A, Grandjean N 2011 Appl. Phys. 109 063720
[3] Holzworth M R, Rudawski N G, Pearton S J, Jones K S, Lu L, Kang T S, Ren F, Johnson J W 2011 Appl. Phys. Lett. 98 122103
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[5] Zhang L, Ding K, Liu N X, Wei T B, Ji X L, Ma P, Yan J C, Wang J X, Zeng Y P, Li J M 2011 Appl. Phys. Lett. 98 101110
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[7] Simon J, Protasenko V, Lian C, Xing H, Jena D 2010 Science 327 60
[8] Zhang L, Ding K, Yan J C, Wang J X, Zeng Y P, Wei T B, Li Y Y, Sun B J, Duan R F, Li J M 2011 Appl. Phys. Lett. 97 062103
[9] Zhong F, Li X H, Qiu K, Yin Z J, Ji C J, Cao X C, Han Q F, Chen J R, Wang Y Q 2007 Chin. Phys. 16 2786
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[11] Jena D 2003 Ph. D. Dissertation (USA: University of California)
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[1] Chang J Y, Liou B T, Lin H W, Shih Y H, Chang S H, Kuo Y K 2011 Opt. Lett. 36 3500
[2] Gonschorek M, Carlin J F, Feltin E, Py M A, Grandjean N 2011 Appl. Phys. 109 063720
[3] Holzworth M R, Rudawski N G, Pearton S J, Jones K S, Lu L, Kang T S, Ren F, Johnson J W 2011 Appl. Phys. Lett. 98 122103
[4] Altahtamouni T M, Sedhain A, Lin J Y, Jiang H X 2008 Appl. Phys. Lett. 92 092105
[5] Zhang L, Ding K, Liu N X, Wei T B, Ji X L, Ma P, Yan J C, Wang J X, Zeng Y P, Li J M 2011 Appl. Phys. Lett. 98 101110
[6] Zhang J F, Wang C, Zhang J C, Hao Y 2006 Chin. Phys. 15 1060
[7] Simon J, Protasenko V, Lian C, Xing H, Jena D 2010 Science 327 60
[8] Zhang L, Ding K, Yan J C, Wang J X, Zeng Y P, Wei T B, Li Y Y, Sun B J, Duan R F, Li J M 2011 Appl. Phys. Lett. 97 062103
[9] Zhong F, Li X H, Qiu K, Yin Z J, Ji C J, Cao X C, Han Q F, Chen J R, Wang Y Q 2007 Chin. Phys. 16 2786
[10] Jena D, Heikman S, Speck J S, Gossard A, Mishra U K 2003 Phys. Rev. B 67 153306
[11] Jena D 2003 Ph. D. Dissertation (USA: University of California)
[12] Li S, Ware M E, Kunets V P, Hawkridge M, Minor P, Wu J, Salamo G J 2011 Phys. Status Solidi C 8 2182
[13] Ridley B K 1998 J. Appl. Phys. 84 4020
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