2010B1962                           BL14B2X ⥺྾཰ᚤ⣽ᵓ㐀 ᐃ࡟ࡼࡿ Eu ῧຍ GaN ࡟࠾ࡅࡿEu ࢖࢜ࣥࡢ࿘㎶ᒁᡤᵓ㐀㻔III㻕
Local Structures around Eu Ions in GaN Studiedby X-ray Absorption Fine Structure㻔III㻕⸨ཎ ᗣᩥ a, すᕝ ᩔ a, ᮤ ᮾᘓ a, ᕝ⁕ ᪸భ a, ኱ῲ ༤ᐉ b, ᮏ㛫 ᚭ⏕ b
Yasufumi Fujiwaraa, Atsushi Nishikawaa, Dongun Leea, Kosuke Kawabataa,
Hironori Ofuchib, Tetsuo Honmaba኱㜰኱Ꮫ, b㻔㈈㻕㧗㍤ᗘග⛉Ꮫ◊✲ࢭࣥࢱ࣮ aOsaka University, b JASRI᭷ᶵ㔠ᒓẼ┦࢚ࣆࢱ࢟ࢩࣕࣝἲ࡟ࡼࡾస〇ࡋࡓ Eu ῧຍ GaN ヨᩱࡢ Eu ࢖࢜ࣥ࿘㎶ᒁᡤᵓ㐀ࢆ X⥺྾཰ᚤ⣽ᵓ㐀㻔XAFS㻕 ᐃ࡟ࡼࡾㄪ࡭ࡓࠋヨᩱస〇᮲௳࡜ࡋ࡚ࠊᡂ㛗 ᗘ࠾ࡼࡧ Eu ὶ㔞ࢆኚ໬ࡉࡏࡿࡇ࡜࡟ࡼࡿ Eu ࢖࢜ࣥ࿘㎶ᒁᡤᵓ㐀࡜ࡢ┦㛵ࢆ᫂ࡽ࠿࡟ࡋࡓࠋῧຍࡉࢀࡓ Eu ࡣ୕౯ࡢ≧ែ
࡛ Ga ࢧ࢖ࢺࢆ⨨᥮ࡋ࡚࠸ࡿࡀࠊ࡜ࡃ࡟ᡂ㛗 ᗘࢆపୗࡉࡏࡿ࡜➨஧㏆᥋ཎᏊ࡛࠶ࡿ Ga ࡟ࡼࡿࣆ࣮ࢡᙉᗘࡀ༢ㄪ࡟ῶᑡࡋࠊ㓄⨨ࡢ஘ࢀࡀ᫂ࡽ࠿࡜࡞ࡗࡓࠋࣇ࢛ࢺ࣑ࣝࢿࢭࣥࢫ㻔PL㻕 ᐃ⤖ᯝ࡜ྜࢃࡏ࡚⪃ᐹࡍࡿ࡜ࠊⓎගࣆ࣮ࢡࡢࣈ࣮ࣟࢻ໬࡜࿘㎶ᒁᡤᵓ㐀ࡢኚ໬ࡀᑐᛂࡋ࡚࠾ࡾࠊ⤖ᬗᡂ㛗᮲௳ࢆไᚚࡍࡿࡇ࡜࡟ࡼࡗ࡚ࠊGaN ୰࡟ῧຍࡋࡓ Eu ࢖࢜ࣥ࡟ࡼࡿⓎගࢆไᚚࡍࡿࡇ࡜ࡀྍ⬟࡛࠶ࡿࡇ࡜ࡀࢃ࠿ࡗࡓࠋ࣮࣮࢟࣡ࢻ㸸 ࣘ࢘ࣟࣆ࣒࢘ࠊ❅໬࣒࢞ࣜ࢘ࠊ㉥ⰍⓎගࢹࣂ࢖ࢫ⫼ᬒ࡜◊✲┠ⓗ㸸GaN ⣔ᮦᩱࡣ࣡࢖ࢻࢠࣕࢵࣉࢆ᭷ࡋࠊ㟷Ⰽࡸ⥳ⰍⓎගࢲ࢖࣮࢜ࢻ㻔LED㻕ࢆᵓᡂࡍࡿ༙ᑟయᮦᩱ࡜ࡋ࡚ᐇ⏝໬ࡉࢀࠊ⾤㢌࡛ぢ࠿ࡅࡽࢀࡿࡼ࠺࡞኱⏬㠃ࣇ࣮ࣝ࢝ࣛLED ࢹ࢕ࢫࣉࣞ࢖࡞࡝࡟ᛂ⏝ࡉࢀ࡚࠸ࡿࠋࡇࢀࡲ࡛ࠊ㉥Ⰽ LED ࡟ࡣ GaN ⣔௨እࡢࠊGaAs ᇶᯈୖ࡟ᡂ㛗ࡉࢀࡓ AlGaInP ࡀ⏝࠸ࡽࢀ࡚ࡁࡓࠋ୍᪉ࠊGaN ⣔ᮦᩱࢆ⏝࠸࡚ࠊ㉥Ⰽ LED ࡀᐇ⌧ࡍࢀࡤࠊྠ୍ᮦᩱ࡟ࡼࡿගࡢ୕ཎⰍⓎගࡀᥞ࠺ࡓࡵࠊ༙ᑟయᚤ⣽ຍᕤᢏ⾡ࢆ⏕࠿ࡋࡓࣔࣀࣜࢩࢵࢡᆺ㧗⢭⣽ LED ࢹ࢕ࢫࣉࣞ࢖ࡸ LED↷᫂࡞࡝࡬ࡢᛂ⏝ࡀྍ⬟࡜࡞ࡿࠋࡇࡢࡓࡵࠊGaN ⣔ᮦᩱࢆ⏝࠸ࡓ㉥ⰍⓎගࢹࣂ࢖ࢫࡢᐇ⌧ࡣࠊ⏘ᴗⓗ࡟ᴟࡵ࡚㔜せ࡞◊✲ㄢ㢟࡜࡞ࡗ࡚࠸ࡿࠋࡇ࠺ࡋࡓ⫼ᬒ࠿ࡽࠊGaN ⣔ᮦᩱ࡟ࡼࡿ㉥Ⰽ LED ᐇ⌧࡟ྥࡅ࡚ࠊ㟷Ⰽ࣭⥳Ⰽ LED ࡛άᛶᒙ࡜ࡋ࡚⏝࠸ࡽࢀ࡚࠸ࡿ InGaN ΰᬗ⣔ࡢ㧗 In ⤌ᡂ໬ࢆ┠ᣦࡋࡓ◊✲ࡀ⢭ຊⓗ࡟⾜ࢃࢀ࡚࠸ࡿࡀࠊInGaN/GaN 㛫ࡢ᱁Ꮚ୙ᩚྜ࡟㉳ᅉࡍࡿ⤖ᬗရ㉁ࡢຎ໬ࡀ῝้࡞ㄢ㢟࡛࠶ࡿࠋ୍᪉ࠊࣘ࢘ࣟࣆ࣒࢘
(Eu)࢖࢜ࣥࡣ 3 ౯ࡢ≧ែ࡛㉥Ⰽ㡿ᇦ࡟ගᏛ㑄⛣ࢆ᭷ࡍࡿࡓࡵࠊGaN ࢆ⏝࠸ࡓ㉥ⰍⓎගᮦᩱࡢⓎග୰ᚰ࡜ࡋ࡚ὀ┠ࡉࢀ࡚࠸ࡿࠋEu ῧຍ GaN స〇᪉ἲ࡜ࡋ࡚ࠊ࢖࢜ࣥὀධἲ࡜ศᏊ⥺࢚ࣆࢱ࢟ࢩࣕࣝἲཬࡧᡃࠎࡢ᭷ᶵ㔠ᒓẼ┦࢚ࣆࢱ࢟ࢩࣕࣝἲࡀᏑᅾࡍࡿࡀࠊ࢖࢜ࣥὀධἲࡸศᏊ⥺࢚ࣆࢱ࢟ࢩࣕࣝἲ࡛ࡣࠕࢹࣂ࢖ࢫရ㉁ࡢ Eu ῧຍ GaNࠖࢆస〇ࡍࡿࡇ࡜ࡀᅔ㞴࡛࠶ࡾࠊࡑࡢస〇ᡭἲ⮬యࡢᐇ⏝ᛶ࡟ࡶ኱ࡁ࡞ㄢ㢟ࢆᢪ࠼࡚࠸ࡿࠋ୍᪉ࠊᡃࠎࡣࠊ᭷ᶵ㔠ᒓẼ┦࢚ࣆࢱ࢟ࢩࣕࣝἲࢆ⏝࠸࡚ 2࢖ࣥࢳࢧ࢖ࢬࡢࢧࣇ࢓࢖࢔ᇶᯈୖ࡟ᆒ୍࡟ Eu ῧຍ GaN ࢆస〇ࡍࡿࡇ࡜࡟ᡂຌࡋࠊGaN ⣔㉥ⰍLED ࡢᐊ ືసࢆୡ⏺࡟ඛ㥑ࡅ࡚ᐇ⌧ࡋ࡚࠸ࡿ[1, 2]ࠋࡼࡗ࡚ࠊGaN ⣔㉥Ⰽ LED ࡢᐇ⏝໬࡟ྥࡅ࡚ࠊ⌧≧ࡢᩘ༑PW ࡢගฟຊࢆ mW ⛬ᗘࡲ࡛ቑ኱ࡉࡏࡿࡇ࡜࡟᭱ᚋࡢㄢ㢟ࡀ⤠ࡽࢀ࡚ࡁ࡚࠸ࡿࠋEu Ⓨගࡣࠊῧຍࡉࢀࡓ Eu ࢖࢜ࣥཎᏊࡢ࿘㎶ᒁᡤᵓ㐀࡟ࡼࡿ⤖ᬗሙ࡟ࡼࡗ࡚Ⓨගຠ⋡ࡀኚ໬ࡍࡿࠋ
ࡇࡢࡓࡵࠊEu Ⓨගᙉᗘࡢᨭ㓄せᅉࡢゎ᫂࡟ࡣࠊGaN ୰࡟࠾ࡅࡿ Eu ࢖࢜ࣥࡢ࿘㎶ᒁᡤᵓ㐀ࢆゎᯒࡍࡿࡇ࡜ࡀ୙ྍḞ࡛࠶ࡿࠋ ᮏᐇ㦂࡛ࡣࠊ᭷ᶵ㔠ᒓẼ┦࢚ࣆࢱ࢟ࢩࣕࣝἲ࡟ࡼࡗ࡚స〇ࡋࡓ Eu ῧຍ GaN ࡟࠾࠸࡚ࠊX ⥺྾཰ᚤ⣽ᵓ㐀㻔XAFS㻕 ᐃ࡟ࡼࡾ Eu ῧຍࢧ࢖ࢺ࠾ࡼࡧࡑࡢ࿘㎶ᒁᡤᵓ㐀ࢆ᫂ࡽ࠿࡟ࡍࡿࡇ࡜ࢆ┠ⓗ࡜ࡍࡿࠋ⤖ᬗᡂ㛗᮲௳࠾ࡼࡧⓎගᙉᗘ࡜ Eu ཎᏊࡢῧຍࢧ࢖ࢺ࠾ࡼࡧࡑࡢ࿘㎶ᒁᡤᵓ㐀ࡢ㛵ಀࢆゎ᫂ࡋࠊ᭷ᶵ㔠ᒓẼ┦࢚ࣆࢱ࢟ࢩࣕࣝἲ࡟ࡼࡗ࡚ῧຍࢧ࢖ࢺࢆ⢭ᐦ࡟ไᚚࡋࠊ㧗㍤ᗘ Eu Ⓨගࡢᐇ⌧ࢆ┠ᣦࡍࠋᐇ㦂㸸ᮏᐇ㦂࡛ࡣࠊ᭷ᶵ㔠ᒓẼ┦࢚ࣆࢱ࢟ࢩࣕࣝἲ࡟ࡼࡾస〇ࡋࡓ Eu ῧຍ GaN ᒙࢆ ᐃヨᩱ࡜ࡋ࡚⏝࠸ࡓࠋヨᩱᵓ㐀ࡣࢧࣇ࢓࢖࢔ᇶᯈୖ࡟ప GaN ࣂࢵࣇ࢓ᒙࠊ↓ῧຍ GaN ᒙࢆ✚ᒙࡋࠊEu ῧຍGaN ᒙࢆ 400 nm ✚ᒙࡋࡓࡶࡢ࡛࠶ࡿࠋヨᩱࡢᡂ㛗 ᗘࢆ 1050, 1000, 950, 900oC ࡜ኚ໬ࡉࡏࡓヨᩱࠊ࠾ࡼࡧ Eu ⃰ᗘࢆ 1.3x1019 ࠿ࡽ 8.7x1019 cm-3 ࡜ኚ໬ࡉࡏࡓヨᩱࢆ‽ഛࡋࡓࠋࣇ࢛ࢺ࣑ࣝࢿࢭࣥ
ࢫ㻔PL㻕 ᐃࡢ⤖ᯝࡼࡾࠊᡂ㛗 ᗘࡀ 1000oC ࡼࡾపࡃ࡞ࡿ࡜Ⓨගࣆ࣮ࢡࡀࣈ࣮ࣟࢻ໬ࡋ࡚࠾ࡾࠊࡲ
ࡓࠊEu ⃰ᗘࡢቑ኱࡟క࠸Ⓨගᙉᗘࡀቑ኱ࡋ࡚࠸ࡃࡇ࡜ࡀほ ࡉࢀ࡚࠸ࡿࠋࡇࢀࡽࡢ PL ᐃ⤖ᯝ࡜࿘㎶ᒁᡤᵓ㐀ࡢ㛵ಀࢆ᫂ࡽ࠿࡟ࡍࡿࡓࡵࠊXAFS ᐃࢆ⾜ࡗࡓࠋᑦࠊXAFS ᐃࡣ࠸ࡎࢀࡢヨᩱࡶ⺯ගἲ࡟࡚⾜ࡗࡓࠋ⤖ᯝ࠾ࡼࡧ⪃ᐹ㸸
ᅗ 1 ࡟ᡂ㛗 ᗘࢆኚ໬ࡉࡏࡓ Eu ῧຍ GaN ࡟࠾ࡅࡿ Eu LIII ྾཰➃ࡢືᚄᵓ㐀㛵ᩘ♧ࡍࠋᡂ㛗
ᗘ 950oC ࡟࠾࠸࡚స〇ࡋࡓヨᩱࡢ XAFS ᐃ⤖ᯝࡀ௒ᅇᚓࡽࢀࡓࢹ࣮ࢱ࡛࠶ࡿࠋῧຍࡉࢀࡓ Eu࢖࢜ࣥࡣ Ga ࢧ࢖ࢺࢆ୕౯ࡢ≧ែ࡛⨨᥮ࡋ࡚࠾ࡾࠊືᚄᵓ㐀㛵ᩘ࡟࠾࠸࡚ Eu ࢖࢜ࣥࡢ➨୍㏆᥋ཎᏊ࡛࠶ࡿ N ࠾ࡼࡧ➨஧㏆᥋ཎᏊ࡛࠶ࡿ Ga ࡟ࡼࡿࣆ࣮ࢡࡀࡑࢀࡒࢀほ ࡉࢀࡓࠋࣇ࢕ࢵࢸ࢕ࣥࢢ࡟ࡼࡾᚓࡽࢀࡓ➨୍㏆᥋ Eu-N ཎᏊ㛫㊥㞳ࡣ⣙ 2.22 ύࠊ➨஧㏆᥋ཎᏊ㛫㊥㞳 Eu-Ga ࡣ⣙ 3.27 ύ࡛࠶ࡾࠊᡂ㛗 ᗘ࡟ࡼࡿཎᏊ㛫㊥㞳ࡢ㐪࠸ࡣぢࡽࢀ࡞࠿ࡗࡓࠋᡂ㛗 ᗘࡀ 1000Υࡼࡾῶᑡࡍࡿ࡟
ᚑ࠸ࠊ➨஧㏆᥋ཎᏊ࡛࠶ࡿ Ga ࡢࣆ࣮ࢡࡀῶᑡࡋ࡚࠾ࡾࠊࡇࢀࡣ Debye-Waller ᅉᏊࡢቑ኱ࢆ♧ࡍࠋࣇ࢕ࢵࢸ࢕ࣥࢢ࡟ࡼࡾᚓࡽࢀࡓ Debye-Waller ᅉᏊࡣᡂ㛗 ᗘࡢῶᑡ࡟క࠸༢ㄪቑຍࡍࡿࡇ࡜ࡀࢃ
࠿ࡾࠊ950oC ࡢヨᩱࢆ ᐃࡍࡿࡇ࡜࡟ࡼࡾࠊୖ㏙ࡋࡓኚ໬ࡀ ᗘ࡟ᑐࡋ࡚⣔⤫ⓗ࡞ኚ໬࡛࠶ࡿࡇ
࡜ࡀࢃ࠿ࡗࡓࠋࡇࢀ࡟ࡼࡾࠊPL ᐃ࡛ほ ࡉࢀࡓᡂ㛗 ᗘపୗ࡟ࡼࡿⓎගࣆ࣮ࢡࡢࣈ࣮ࣟࢻ໬ࡀ
࿘㎶ᒁᡤᵓ㐀ࡢኚ໬࡜ࡋ࡚ㄝ࡛᫂ࡁࡿࡇ࡜ࡀ᫂ࡽ࠿࡜࡞ࡗࡓࠋ
ᅗ 2 ࡟ Eu ὶ㔞ࢆኚ໬ࡉࡏࡓ Eu ῧຍ GaN ࡟࠾ࡅࡿ Eu LIII ྾཰➃ࡢືᚄᵓ㐀㛵ᩘࢆ♧ࡍࠋEu ౪⤥᪉ἲࡢ᭱㐺໬࡟ࡼࡾ 8.7x1019 cm-3 ࡲ࡛ Eu ⃰ᗘࢆቑຍࡉࡏࡓヨᩱ࡟ࡘ࠸࡚ XAFS ᐃࢆ⾜ࡗࡓࠋEu ὶ㔞ࡢቑ኱࡟క࠸ࠊPL ᙉᗘࡢቑ኱ࡀほ ࡉࢀ࡚࠸ࡿࡀࠊືᚄᵓ㐀㛵ᩘ࠿ࡽࡣཎᏊ㛫㊥㞳ཬࡧࣆ࣮ࢡᙉᗘ࡟ࡣኚ໬ࡀぢࡽࢀ࡞࠿ࡗࡓࠋࡇࢀࡣ 8.7x1019 cm-3 ࡲ࡛ Eu ⃰ᗘࢆቑ኱ࡋ࡚ࡶࠊ౫↛࡜ࡋ࡚ῧຍࡉࢀࡓ Eu ࡀ஫࠸࡟ᙳ㡪ࢆ୚࠼ࡎ⊂❧࡟ Ga ࢧ࢖ࢺࢆ⨨᥮ࡋ࡚࠸ࡿࡇ࡜ࢆ♧ࡋ࡚࠾ࡾࠊEu⃰ᗘࢆ㧗⃰ᗘ໬ࡍࡿࡇ࡜࡟ࡼࡾ᭦࡞ࡿ㧗㍤ᗘ໬ࡀྍ⬟࡛࠶ࡿࡇ࡜ࡀࢃ࠿ࡗࡓࠋ       ᅗ 2㸬Eu ⃰ᗘࢆኚ໬ࡉࡏࡓ Eu ῧຍ GaN ࡟ᅗ 1㸬ᡂ㛗 ᗘࢆኚ໬ࡉࡏࡓ Eu ῧຍ GaN
࠾ࡅࡿ Eu LIII ྾཰➃ࡢືᚄᵓ㐀㛵ᩘ࡟࠾ࡅࡿ Eu LIII ྾཰➃ࡢືᚄᵓ㐀㛵ᩘࡉࡽ࡟ࠊSIMS ᐃ࡟ࡼࡾ Eu ⃰ᗘࢆྠᐃࡋࡓヨᩱ㻔4 ヨᩱ㻕ࢆᶆ‽ヨᩱ࡜ࡋ࡚ᨺᑕග⺯ග X ⥺ᐃࢆ⾜ࡗࡓࠋᅗ 3 ࡟⺯ග X ⥺ࢫ࣌ࢡࢺࣝࢆ♧ࡍࠋᅗ 3 ᤄධᅗ࡟♧ࡍࡼ࠺࡟ EuLDࣆ࣮ࢡ࡜ Eu ⃰ᗘ࡟ࡣẚ౛㛵ಀࡀ࠶ࡾࠊྛ Eu ⃰ᗘ࡟ࡼࡗ࡚ᚓࡽࢀࡓ⺯ග X ⥺ᙉᗘࢆ᳨㔞⥺࡜ࡋࠊEu ⃰ᗘࡀᮍ▱ࡢヨᩱ࡟ࡘ࠸࡚⃰ᗘࡢྠᐃࢆ⾜࠺ࡇ࡜ࡀྍ⬟࡛࠶ࡿࠋᨺᑕගࢆ⏝࠸ࡓ⺯ග X ⥺ ᐃࢆ⾜࠺ࡇ࡜࡟ࡼࡾࠊῧຍ⃰ᗘࡀ 1019 cm-3 ࣮࢜ࢲ࣮࡜ GaN ୰࡟ᚤ㔞࡟ῧຍࡋࡓ Eu ࡟࠾࠸࡚ࡶࠊs5%ࡢ⢭ᗘ࡛⃰ᗘࡢྠᐃࡀྍ⬟࡛࠶ࡿࡇ࡜ࡀࢃ࠿ࡗࡓࠋ

ᅗ 3㸬Eu ῧຍ GaN ࡟࠾ࡅࡿ⺯ග X ⥺ࢫ࣌ࢡࢺࣝ
㸦ᤄධᅗ࡜ࡋ࡚ࠊEuLDࣆ࣮ࢡ࡜ SIMS ᐃ࡟ࡼࡗ࡚ྠᐃࡋࡓ Eu ⃰ᗘࡢ㛵ಀࢆ♧ࡍ㸧௒ᚋࡢㄢ㢟㸸 ௒ᅇࡢ ᐃ⤖ᯝ࡟ࡼࡾࠊᡂ㛗 ᗘࡀ Eu ࢖࢜ࣥࡢ࿘㎶ᒁᡤᵓ㐀࡟୚࠼ࡿᙳ㡪ࢆ⣔⤫ⓗ࡟ㄪ࡭ࡿࡇ࡜ࡀ࡛ࡁࡓࠋ࡜ࡃ࡟Ⓨගࣆ࣮ࢡ⥺ᖜࡢไᚚ࡟ࡣࠊGaN ࡟ῧຍࡉࢀࡓ Eu ࢖࢜ࣥࡢ࿘㎶ᒁᡤᵓ㐀ࡢไᚚࡀᚲ㡲࡛࠶ࡿࡇ࡜ࡀࢃ࠿ࡗࡓࠋࡲࡓࠊ㧗⃰ᗘ໬ࡋࡓヨᩱ࡟ࡘ࠸࡚ࡶ౫↛࡜ࡋ࡚ῧຍ Eu 㛫ࡢ┦஫స⏝ࡣᑠࡉࡃࠊᒁᡤᵓ㐀࡟ࡣᙳ㡪ࢆ୚࠼࡞࠸ࡇ࡜ࡀࢃ࠿ࡗࡓࠋࡇࡢ⤖ᯝࡼࡾࠊ᭦࡞ࡿ Eu⃰ᗘቑ኱ࡀⓎගࡢ㧗㍤ᗘ໬࡟᭷ຠ࡛࠶ࡿࡓࡵࠊẕయࡢ⤖ᬗᛶࢆⰋዲ࡟ಖࡕࡘࡘࠊEu ࢖࢜ࣥࡢ㧗⃰ᗘῧຍࢆ୧❧ࡉࡏࡓᡂ㛗᮲௳ࢆ᥈⣴ࡍࡿࡇ࡜ࡀᚲせ࡛࠶ࡿࠋཧ⪃ᩥ⊩㸸
[1] A. Nishikawa, T. Kawasaki, N. Furukawa, Y. Terai, and Y. Fujiwara, Appl. Phys. Exp. 2, 071004 㻔2009㻕.
[2] A. Nishikawa, T. Kawasaki, N. Furukawa, Y. Terai, and Y. Fujiwara, Phys. Status Solidi A 207, 1938
㻔2010㻕.