2010B1844                           BL14B2X ⥺྾཰ᚤ⣽ᵓ㐀 ᐃ࡟ࡼࡿ Eu ῧຍ GaN ࡟࠾ࡅࡿEu ࢖࢜ࣥࡢ࿘㎶ᒁᡤᵓ㐀㻔II㻕Local Structures around Eu Ions in GaN Studiedby X-ray Absorption Fine Structure㻔II㻕⸨ཎ ᗣᩥ a, すᕝ ᩔ a, ྂᕝ ┤ᶞ a, ᕝ⁕ ᪸భ a, ᯇ㔝 Ꮥ๎ a, ኱ῲ ༤ᐉ b, ᮏ㛫 ᚭ⏕ b
Yasufumi Fujiwaraa, Atsushi Nishikawaa, Naoki Furukawaa, Kosuke Kawabataa, Takanori Matsunoa,
Hironobu 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௳࡜ࡋ࡚ࠊ࢔ࣥࣔࢽ࢔ὶ㔞࠾ࡼࡧ Eu ὶ㔞ࢆኚ໬ࡉࡏࡿࡇ࡜࡛ࠊEu ࢖࢜ࣥ࿘㎶ᒁᡤᵓ㐀ࡀኚ໬ࡍࡿࡇ࡜ࢆ᫂ࡽ࠿࡟ࡋࡓࠋῧຍࡉࢀࡓ Eu ࡣ୕౯ࡢ≧ែ࡛ Ga ࢧ࢖ࢺࢆ⨨᥮ࡋ࡚࠸ࡿࡀࠊ࡜ࡃ࡟࢔ࣥࣔࢽ࢔ὶ㔞ࡢኚ໬࡟ࡼࡾ➨஧㏆᥋ཎᏊ࡛࠶ࡿ Ga ࡟ࡼࡿࣆ࣮ࢡᙉᗘ࡟㢧ⴭ࡞㐪࠸ࡀ⌧ࢀࡓࠋࣇ࢛ࢺ࣑ࣝࢿࢭࣥࢫ㻔PL㻕 ᐃ࡞࡝௚ࡢ ᐃ⤖ᯝ࡜ྜࢃࡏ࡚⪃ᐹࡍࡿ࡜ࠊⓎගࣆ࣮ࢡࡢඛ㗦໬࡜࿘㎶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㻔Eu㻕࢖࢜ࣥ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⥺࢚ࣆࢱ࢟ࢩ
ࣕࣝἲ࡛ࡣࠕࢹࣂ࢖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࠸ࡿࠋ
Eu Ⓨ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ヨᩱࡢ࢔ࣥࣔࢽ࢔ὶ㔞ࢆ 2, 4, 6 SLM㻔V/III ẚ 3200, 6400,9600㻕࡜ኚ໬ࡉࡏࡓヨᩱࠊ࠾ࡼࡧ Eu ὶ㔞ࢆ 0.5, 1.0, 1.5, 1.9 sccm㻔Eu ⃰ᗘ 1.3x1019, 2.3x1019, 3.8x1019,
19-3
5.2x10 cm 㻕࡜ኚ໬ࡉࡏࡓヨᩱࢆ‽ഛࡋࡓࠋࣇ࢛ࢺ࣑ࣝࢿࢭࣥࢫ㻔PL㻕 ᐃࡢ⤖ᯝࡼࡾࠊ࢔ࣥࣔࢽ
࢔ὶ㔞ࡀῶᑡࡍࡿ࡟ࡘࢀ࡚Ⓨගࣆ࣮ࢡࡀඛ㗦໬ࡋ࡚࠾ࡾࠊEu ⃰ᗘࡢቑ኱࡟క࠸Ⓨගᙉᗘࡀቑ኱ࡋ
࡚࠸ࡃࡇ࡜ࡀほ ࡉࢀ࡚࠸ࡿࠋXAFS ᐃࡣ࠸ࡎࢀࡢヨᩱࡶ⺯ගἲ࡟࡚⾜ࡗࡓࠋ⤖ᯝ࠾ࡼࡧ⪃ᐹ㸸ᅗ 1 ࡟࢔ࣥࣔࢽ࢔ὶ㔞ࢆኚ໬ࡉࡏࡓ Eu ῧຍ GaN ࡟࠾ࡅࡿ Eu LIII ྾཰➃ࡢືᚄᵓ㐀㛵ᩘࢆ♧ࡍࠋῧຍࡉࢀࡓ Eu ࢖࢜ࣥࡣ Ga ࢧ࢖ࢺࢆ⨨᥮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⣙ 2.24 ύࠊ➨஧㏆᥋ཎᏊ㛫㊥㞳 Eu-Ga ࡣ⣙ 3.27
ύ࡛࠶ࡾࠊ࢔ࣥࣔࢽ࢔ὶ㔞࡟ࡼࡿཎᏊ㛫㊥㞳ࡢ㐪࠸ࡣぢࡽࢀ࡞࠿ࡗࡓࠋࡋ࠿ࡋࠊ࢔ࣥࣔࢽ࢔ὶ㔞ࡀῶᑡࡍࡿ࡟ᚑ࠸ࠊ➨஧㏆᥋ཎᏊ࡛࠶ࡿ Ga ࡢࣆ࣮ࢡࡀቑ኱ࡋ࡚࠾ࡾࠊࡇࢀࡣ Debye-Waller ᅉᏊࡀᑠࡉࡃ࡞ࡗ࡚࠸ࡿࡇ࡜ࢆ♧ࡍࠋࡇࡢࡓࡵࠊEu ࢖࢜ࣥࡢ㏆᥋ཎᏊࡢ⨨᥮ࢧ࢖ࢺࡢᦂࡽࡂࡀᑠࡉࡃࠊ
ᆒ୍ᛶࡢⰋዲ࡞⤖ᬗ࡜࡞ࡗ࡚࠸ࡿࡇ࡜ࡀࢃ࠿ࡗࡓࠋPL ᐃࡢ⤖ᯝ࠿ࡽ࢔ࣥࣔࢽ࢔ὶ㔞ࡢῶᑡ࡟ᚑ࠸ࠊⓎගࣆ࣮ࢡࡢඛ㗦໬ࡀほ ࡉࢀ࡚࠸ࡿࡓࡵࠊᆒ୍ᛶࡢⰋዲ࡞⤖ᬗ࡟࡞ࡿ࡯࡝ࠊࣆ࣮ࢡࡀඛ㗦໬ࡍࡿࡇ࡜ࡀࢃ࠿ࡗࡓࠋᅗ 2 ࡟ Eu ὶ㔞ࢆኚ໬ࡉࡏࡓ Eu ῧຍ GaN ࡟࠾ࡅࡿ Eu LIII ྾཰➃ࡢືᚄᵓ㐀㛵ᩘࢆ♧ࡍࠋEu ὶ㔞ࡀቑ኱ࡍࡿࡇ࡜࡟ࡼࡿ PL Ⓨගᙉᗘࡢቑ኱ࡀほ ࡉࢀ࡚࠸ࡿࡀࠊືᚄᵓ㐀㛵ᩘ࠿ࡽࡣୖグࡢ࢔ࣥࣔࢽ࢔ὶ㔞౫Ꮡᛶࡢࡼ࠺࡞ࣆ࣮ࢡᙉᗘࡢ᭷ព࡞ኚ໬ࡣぢࡽࢀ࡞࠿ࡗࡓࠋࡇࢀࡣ௒ᅇ ᐃࡋࡓヨᩱࡢ Eu ⃰ᗘ⠊ᅖ㻔<5.2x1019 cm-3㻕࡛ࡣῧຍࡉࢀࡓ Eu ࢖࢜ࣥࡀ஫࠸࡟ᙳ㡪ࢆ୚࠼ࡎ⊂❧࡟ Ga ࢧ࢖ࢺࢆ⨨᥮ࡋ࡚࠸ࡿࡇ࡜ࢆ♧ࡋ࡚࠾ࡾࠊྠᵝࡢ࿘㎶ᒁᡤᵓ㐀ࢆ᭷ࡍࡿ Eu ⃰ᗘࡀቑ኱ࡋ࡚࠸ࡿࡇ࡜ࡀ
ࢃ࠿ࡗࡓࠋࡇࡢࡓࡵࠊ㧗㍤ᗘⓎග࡟ࡣ᭦࡞ࡿ Eu ⃰ᗘࡢቑ኱ࡀ᭷ຠ࡛࠶ࡿࡇ࡜ࡀ♧ࡉࢀࡓࠋ  ᅗ 1㸬࢔ࣥࣔࢽ࢔ὶ㔞ࢆኚ໬ࡉࡏࡓ Eu ῧຍGaN ࡟࠾ࡅࡿ Eu LIII ྾཰➃ࡢືᚄᵓ㐀㛵ᩘᅗ 2㸬Eu ⃰ᗘࢆኚ໬ࡉࡏࡓ Eu ῧຍ GaN ࡟࠾ࡅࡿ Eu LIII ྾཰➃ࡢືᚄᵓ㐀㛵ᩘ௒ᚋࡢㄢ㢟㸸 ௒ᅇࡢ⤖ᯝ࡟ࡼࡾࠊ࢔ࣥࣔࢽ࢔ὶ㔞ࡀ Eu ࢖࢜ࣥࡢ࿘㎶ᒁᡤᵓ㐀࡟኱ࡁ࡞ᙳ㡪ࢆ୚࠼ࡿࡇ࡜ࡀ᫂ࡽ࠿࡜࡞ࡗࡓࠋ࡜ࡃ࡟Ⓨගࣆ࣮ࢡࡢඛ㗦໬࡟ࡣࠊGaN ࡟ῧຍࡉࢀࡓ Eu ࢖࢜ࣥࡢ࿘㎶ᒁᡤᵓ㐀ࡢไᚚࡀᚲ㡲࡛࠶ࡿࠋࡲࡓࠊ௒ᅇࡢᐇ㦂ࢆ⾜ࡗࡓ Eu ⃰ᗘ⠊ᅖ࡛ࡣࠊ⨨᥮ࢧ࢖ࢺཬࡧ࿘㎶ᒁᡤᵓ㐀࡟ࡣῧຍࡉࢀࡓ Eu ࢖࢜ࣥ㛫ࡢ┦஫స⏝ࡣᑠࡉࡃࠊ᭦࡞ࡿ Eu ⃰ᗘቑ኱ࡀⓎගࡢ㧗㍤ᗘ໬࡟᭷ຠ࡛࠶ࡿࡇ࡜ࡀࢃ࠿ࡗࡓࠋཧ⪃ᩥ⊩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.