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β-Ga2O3 単結晶における自己束縛励起子の安定性の評価
E-Ga2O3 ༢⤖ᬗ䛻䛚䛡䜛⮬ᕫ᮰⦡ບ㉳Ꮚ䛾Ᏻᐃᛶ䛾ホ౯ ᒣᒸඃ䚸୰ᒣṇ 㜰ᕷ❧ᏛᏛ㝔ᕤᏛ◊✲⛉㟁Ꮚሗ⣔ᑓᨷ Characterization of stability of self-trapped excitons in a E-Ga2O3 single crystal Suguru Yamaoka and Masaaki Nakayama Department of Applied Physics, Graduate School of Engineering, Osaka City University We have investigated photoluminescence (PL) and absorption properties of a E-Ga2O3 single crystal from the viewpoint of the stability of self-trapped excitons (STEs). A broad PL band with a large Stokes shift, which is conventionally assigned to the STE, was observed. To reveal the stability of the STE, we precisely measured the temperature dependence of the Urbach tails in absorption spectra. It was confirmed that Urbach tails at all temperatures converge into a given point, which verifies the validity of the treatment of the Urbach tail. We analysed the temperature dependence of the exponential slope, the so-called steepness constant, of the Urbach tail and evaluated the exciton-phonon coupling constant g, which defines the stability of the STE, to be g=5.4. Based on a previously reported theory for exciton-phonon interactions, g>1 generally results in that the STE is a stable state relative to a free exciton. Consequently, the above large g factor demonstrates that the STE formation is stable in E-Ga2O3. 1. ࡣࡌࡵ 㓟≀༙ᑟయ࡛࠶ࡿE-Ga2O3 ࡣࠊᚑ᮶ࡢࣃ ࣮࣡ࢹࣂࢫ⏝࠸ࡽࢀ࡚࠸ࡿ࣡ࢻࢠࣕ ࢵࣉ༙ᑟయ࡛࠶ࡿ GaN ࡸ SiC ẚ࡚ࠊ ࡁ࡞ࣂࣥࢻࢠࣕࢵࣉ࢚ࢿࣝࢠ࣮(4.7 eV)ࢆ ࡶࡘࡇࡽ[1]ࠊࡼࡾ୍ᒙࡢపᦆኻࠊ㧗⪏ ᅽࡢࢹࣂࢫ≉ᛶࢆᣢࡘࡇࡀᮇᚅࡉࢀ࠾ ࡾࠊ㏆ᖺࠊE-Ga2O3 ࢆ⏝࠸ࡓ FET ࡀ㛤Ⓨࡉ ࢀ[2]ࠊࡁ࡞ὀ┠ࡀ㞟ࡲࡗ࡚࠸ࡿࠋࡉࡽࠊ E-Ga2O3 ࡣ㏱᫂ᑟ㟁⭷ࠊ῝⣸እග᳨ฟჾ➼ ࡶᛂ⏝ࡉࢀ࡚࠸ࡿ[3-6]ࠋ E-Ga2O3 ࡣ༢ᩳᬗᵓ㐀ࢆࡿ[7]ࠋ྾ࢫ ࣌ࢡࢺࣝࡣࠊb ㍈ࠊཬࡧࠊc ㍈ᑐࡋ࡚೫ග ≉ᛶࢆ♧ࡍ[8-11]ࠋE-Ga2O3 ࡽࡢⓎගࡣࠊ 㠀ᖖࣈ࣮ࣟࢻ࡛࠶ࡾࠊࡁ࡞ࢫࢺ࣮ࢡࢫ ࢩࣇࢺࢆక࠺ࡇࡀሗ࿌ࡉࢀ࡚࠸ࡿ[10, 11]ࠋ ࡇࡢࣈ࣮ࣟࢻ࡞Ⓨගᖏࡣࠊ⌧㇟ㄽⓗࠊ⮬ ᕫ᮰⦡ṇᏍࡑࡢṇᏍࡽ࠼ࡽࢀࡓ㟁Ꮚ ࡽᵓᡂࡉࢀࡿ⮬ᕫ᮰⦡ບ㉳Ꮚࡽࡢࡶࡢ ࡛࠶ࡿ⪃࠼ࡽࢀ࡚࠸ࡿ[10, 11]ࠋ⮬ᕫ᮰⦡ 267 ບ㉳Ꮚࡣ࠾ࡶࠊࣝ࢝ࣜࣁࣛࢻ࡛ほ ࡉࢀࡿ[12]ࠋE-Ga2O3 ࠾࠸࡚ࠊVarley ࡽࡢ ⌮ㄽィ⟬ᇶ࡙ࡃ[13]ࠊ㔜࠸᭷ຠ㉁㔞ࢆࡶ ࡘṇᏍࡣࠊ᱁Ꮚṍࡳࢆకࡗ࡚ᒁᅾࡍࡿࠋ ࡑࡋ࡚ࠊᑠࡉ࡞࣏࣮ࣛࣟࣥ(⮬ᕫ᮰⦡ṇᏍ) ࡀᙧᡂࡉࢀࠊ⮬ᕫ᮰⦡ṇᏍࡣࠊ㓟⣲ཎᏊࡢ 2p ㌶㐨ᒁᅾࡍࡿሗ࿌ࡉࢀ࡚࠸ࡿࠋࡋ ࡋ࡞ࡀࡽࠊE-Ga2O3 ࠾࠸࡚ࠊ⮬ᕫ᮰⦡ບ ㉳ᏊᙧᡂࡢᏳᐃᛶ㛵ࡍࡿ᫂☜࡞ᐇ㦂ⓗド ᣐࡣࠊࡇࢀࡲ࡛ሗ࿌ࡉࢀ࡚࠸࡞࠸ࠋ Schreiber ㇏ἑࡼࡿບ㉳Ꮚ-᱁Ꮚ┦ స⏝㛵ࡍࡿ⌮ㄽࡼࡿ[14]ࠊ⮬⏤ບ㉳Ꮚ ẚ㍑ࡋࡓ⮬ᕫ᮰⦡ບ㉳ᏊࡢᏳᐃᛶࡣࠊ྾ ࢫ࣌ࢡࢺࣝ⌧ࢀࡿᣦᩘ㛵ᩘⓗ࡞ࡩࡿࡲ ࠸ࢆ♧ࡍప࢚ࢿࣝࢠ࣮ഃࡢ〈(࣮ࣂࢵࢡ ࢸࣝ)ࡢゎᯒࡽồࡲࡿບ㉳Ꮚ̿᱁Ꮚ┦ స⏝ᐃᩘ g ࡽ᫂ࡽ࡞ࡿࠋg ࡀ 1 ࡼ ࡾࡁ࠸ሙྜࠊ୍⯡ⓗ⮬ᕫ᮰⦡ບ㉳Ꮚࡣࠊ ⮬⏤ບ㉳Ꮚẚ࡚Ᏻᐃ࡞ࡿࠋᮏ◊✲࡛ ࡣࠊE-Ga2O3 ༢⤖ᬗ࠾࠸࡚ࠊ࣮ࣂࢵࢡࢸ 2. ヨᩱᐇ㦂᪉ἲ ᮏ◊✲࡛⏝࠸ࡓヨᩱࡣࠊ⼥ᾮᡂ㛗ἲࡼ ࡾ (010) 㠃 ᪉ ᡂ 㛗 ࡉ ࢀ ࡓ ࣥ ࢻ ࣮ ࣉ E-Ga2O3 ༢⤖ᬗ࡛࠶ࡿ(ࢱ࣒ࣛ〇సᡤస〇)ࠋ ヨᩱࡢཌࡉࡣ 0.60 mm ࡛࠶ࡿࠋගᏛ ᐃࡣ ྾ࠊⓎගࠊཬࡧࠊⓎගບ㉳ࢫ࣌ࢡࢺࣝࡢ ᐃࢆ⾜ࡗࡓࠋ྾ࢫ࣌ࢡࢺࣝࡢ ᐃࡣࠊ ࢲࣈࣝࣅ࣮࣒ᆺศගගᗘィ(ศゎ⬟ 0.1 nm) ࢆ⏝࠸ࠊ10 K ࡽ 280 K ࡲ࡛ࡢ ᗘ౫Ꮡᛶ ࢆ⣔⤫ⓗ ᐃࡋࡓࠋࡲࡓࠊⓎගࢫ࣌ࢡࢺ ࣝࡣࠊບ㉳ග※ YAG ࣮ࣞࢨ࣮ࡢ➨ 5 㧗ㄪ Ἴࢆ⏝࠸ࠊ࣐ࣝࢳࢳࣕࣥࢿࣝศගჾ᳨࡛ฟ ࡋࡓ(ศゎ⬟ 1.5 nm)ࠋⓎගບ㉳ࢫ࣌ࢡࢺࣝࡢ ບ㉳ග※ࡣࠊࣉࣜࢬ࣒ศගჾࡼࡗ࡚༢ Ⰽࡉࢀࡓ㔜Ỉ⣲ࣛࣥࣉࢆ⏝࠸ࠊࣇ࢛ࢺࣥ ࢝࢘ࣥࢸࣥࢢࢩࢫࢸ᳨࣒࡛ฟࡋࡓ(ศゎ ⬟ 1.4 nm)ࠋ࡞࠾ࠊⓎගࠊⓎගບ㉳ࢫ࣌ࢡࢺ ࣝࡣࠊ10 K ࡛ ᐃࢆ⾜ࡗࡓࠋ 3. ᐇ㦂⤖ᯝ⪃ᐹ ᅗ 1 ࡣࠊE-Ga2O3 ༢⤖ᬗࡢ 10 K ࠾ࡅࡿ Ⓨගࢫ࣌ࢡࢺࣝࠊཬࡧࠊ▮༳ࡢ࢚ࢿࣝࢠ࣮ ࡛ཷගࡋࡓⓎගບ㉳ࢫ࣌ࢡࢺࣝࢆ⾲ࡋ࡚࠸ PL PLE det. Normalized PL Intensity 10 K 2.0 3.0 4.0 5.0 Absorption Coefficient (cm-1) ࣝࡢ ᗘ౫Ꮡᛶࢆ⣔⤫ⓗ ᐃࡋࠊࡑࡢ ⤖ᯝࢆཧ⪃ᩥ⊩[14, 15]ᇶ࡙࠸࡚ゎᯒࡋࡓࠋ ࡑࡢ⤖ᯝࠊ⮬ᕫ᮰⦡ບ㉳ᏊࡢᏳᐃᛶࡀ᫂ࡽ ࡞ࡗࡓࠋ 103 102 280 K 10 10 K 30 K step 4.4 4.6 4.8 5.0 Photon Energy (eV) ᅗ 2. β-Ga2O3 ༢⤖ᬗ࠾ࡅࡿ྾ࢫ࣌ࢡࢺࣝ ࡢ ᗘ౫Ꮡᛶࠋᐇ⥺ࡣᐇ㦂⤖ᯝࠊ◚⥺ࡣᘧ(1) ᇶ࡙࠸ࡓࣇࢵࢸࣥࢢ⤖ᯝࢆ♧ࡋ࡚࠸ ࡿࠋ ࡿࠋᅗ 1 ࠾࠸࡚ࠊⓎගບ㉳ࢫ࣌ࢡࢺࣝࡢ ࣆ࣮ࢡࢆᇶ‽ 1.5 eV ࡢࢫࢺ࣮ࢡࢫࢩࣇࢺ ࢆకࡗࡓࣈ࣮ࣟࢻ࡞Ⓨගࣂࣥࢻࡀࠊほ ࡉ ࢀࡓࠋ୍⯡ⓗࠊ⮬ᕫ᮰⦡ບ㉳ᏊࡽࡢⓎ ගࡣࠊᙉ࠸᱁Ꮚ⦆ࡼࡗ࡚ࠊࡁ࡞ࢫࢺ ࣮ࢡࢫࢩࣇࢺࢆకࡗࡓࣈ࣮ࣟࢻ࡞Ⓨගࡀほ ࡉࢀࡿࠋࡺ࠼ࠊᅗ 1 ࡢⓎගࡣࠊ⌧㇟ㄽ ⓗ⮬ᕫ᮰⦡ບ㉳Ꮚࡽࡢࡶࡢ࡛࠶ࡿ⪃ ࠼ࡽࢀ࡚࠸ࡿ[10, 11]ࠋ ᅗ 2 ࡣ྾ࢫ࣌ࢡࢺࣝ⌧ࢀࡿ࣮ࣂࢵ ࢡࢸࣝࡢ ᗘ౫Ꮡᛶࡢ⤖ᯝࢆ 10 K ࡽ 280 K ࡲ࡛ࠊ30 K ࡈᐇ⥺࡛⾲♧ࡋ࡚࠸ ࡿࠋᅗ 2 ࠾࠸࡚ࠊ࣮ࣂࢵࢡࢸࣝᑐ ᛂࡍࡿᣦᩘ㛵ᩘⓗ࡞〈ࢆ᫂☜ほ ࡋࡓࠋ ࡲࡓࠊ࡚ࡢ ᗘ࡛ࢫࢸࢵࣉᵓ㐀ࡀほ ࡉ ࢀࡓࠋࡇࢀࡣࠊගᏛ␗᪉ᛶ㉳ᅉࡍࡿ⪃ ࠼ࡽࢀࡿ[8-11]ࠋࡇࡢゎᯒ࡛ࡣࠊ⡆༢ࡢࡓࡵࠊ ప࢚ࢿࣝࢠ࣮ഃࡢ࣮ࣂࢵࢡࢸࣝࡔࡅࢆ ྲྀࡾᢅ࠺ࠋ࣮ࣂࢵࢡࢸࣝࡣ௨ୗࡢᘧ࡛ ⾲ࡉࢀࡿ[14]ࠋ α Photon Energy (eV) ᅗ 1. 10 K ࠾ࡅࡿE-Ga2O3 ࡢⓎග(ᐇ⥺) Ⓨගບ㉳ࢫ࣌ࢡࢺࣝ(㯮)ࠋ▮༳ࡣⓎග ບ㉳ࢫ࣌ࢡࢺࣝࡢཷග࢚ࢿࣝࢠ̿ࢆ♧ࡋ ࡚࠸ࡿࠋ 104 ª E Eº α 0 exp « σ (T ) 0 » k BT ¼ ¬ (1) ࡇࡇ࡛ࠊE0 ࡣᴟప ࡛ࡢບ㉳Ꮚ࢚ࢿࣝࢠ࣮ ᑐᛂࡍࡿ᮰࢚ࢿࣝࢠ̿ࠊ V(T)ࡣ ᗘ ౫Ꮡࡍࡿࢫࢸ࣮ࣉࢿࢫಀᩘ࡛࠶ࡿࠋᅗ 2 268 E 0.2 V(T) B Ea B EST ELR 0.1 0 0 100 200 300 ELR Temperature (K) Q ᅗ 4. ⮬⏤ບ㉳Ꮚࠊཬࡧࠊ⮬ᕫ᮰⦡ບ㉳Ꮚ ᅗ 3. ࣮ࣂࢵࢡࢸࣝࡢഴࡁࡽᚓࡽࢀࡓ ࢫࢸ࣮ࣉࢿࢫಀᩘࡢ ᗘ౫Ꮡᛶࠋ㯮ࡣᐇ 㦂⤖ᯝࠊᐇ⥺ࡣᘧ(2)ᇶ࡙࠸ࡓࣇࢵࢸࣥ ࢢ⤖ᯝࢆ♧ࡋ࡚࠸ࡿࠋ ᑐࡍࡿ㓄ᗙᶆࣔࢹࣝࠋᶓ㍈ࡣ᱁Ꮚṍࡳ Q ࢆ ⾲ࡍࠋ ⾲ࡉࢀࡿࠋ ࡢ◚⥺ࡣࠊᘧ(1)ᇶ࡙࠸ࡓࣇࢵࢸࣥࢢ ⤖ᯝࢆ♧ࡋ࡚࠾ࡾࠊ◚⥺ࡣ࠶ࡿ୍Ⅼ᮰ ࡍࡿ⤖ᯝࡀᚓࡽࢀࡓࠋࡇࡢ⤖ᯝࡣࠊ࣮ࣂ ࢵࢡࢸࣝࡢྲྀࡾᢅ࠸ࡀࠊጇᙜ࡛࠶ࡿࡇ ࢆ♧ࡋ࡚࠸ࡿࠋࡇࡢ᮰Ⅼࡽ᮰࢚ࢿࣝ ࢠ̿E0=4.98 eV, D0=5.3103 cm-1 ồࡲࡗ ࡓࠋ᮰࢚ࢿࣝࢠ̿E0 ࡣࠊ10 K ࠾ࡅࡿⓎ ගບ㉳ࢫ࣌ࢡࢺ࡛ࣝᚓࡽࢀࡓࣆ࣮ࢡ࢚ࢿࣝ ࢠ࣮4.9 eV ࡰ୍⮴ࡋ࡚࠸ࡿࠋ ᅗ 3 ࡢ㯮ࡣࠊ࣮ࣂࢵࢡࢸࣝࡢഴࡁ ࡽᚓࡽࢀࡓࢫࢸ࣮ࣉࢿࢫಀᩘ V(T)ࡢ ᗘ౫Ꮡᛶࡢ⤖ᯝࢆ⾲ࡋ࡚࠸ࡿࠋᩥ⊩[15]ᇶ ࡙ࡃࠊࢫࢸ࣮ࣉࢿࢫಀᩘ V(T)ࡢ ᗘ౫ Ꮡᛶࡣࠊ σ (T ) σ0 ª E ph º 2 k BT tanh « » E ph ¬ 2 k BT ¼ g E LR B (3) ࡇࡇ࡛ࠊELR ࡣ᱁Ꮚ⦆࢚ࢿࣝࢠ̿ࠊB ࡣບ ㉳Ꮚࣂࣥࢻ༙ᖜ࡛࠶ࡿࠋᅗ 4 ࡣࠊ⮬⏤ບ㉳ Ꮚࠊཬࡧࠊ⮬ᕫ᮰⦡ບ㉳Ꮚᑐࡍࡿ㓄ᗙ ᶆࣔࢹࣝࢆ⾲ࡋ࡚࠸ࡿࠋg ࡀ 1 ࡼࡾࡁ࠸ ሙྜࠊ⮬ᕫ᮰⦡≧ែࡀ᭱ప࢚ࢿࣝࢠ̿࡞ ࡾࠊ⮬⏤ບ㉳Ꮚẚ࡚ࠊ⮬ᕫ᮰⦡ບ㉳Ꮚ ࡀᏳᐃ࡞ࡿࠋg ࡣࡲࡓࠊ௨ୗࡢᘧ࡛ࡶᐃ ⩏ࡉࢀࡿ[14]ࠋ g s σ0 (4) ࡇࡇ࡛ࠊs ࡣḟඖ౫Ꮡࡍࡿࢫࢸ࣮ࣉࢿࢫ ᐃᩘ࡛࠶ࡿࠋ3 ḟඖ⤖ᬗ࡛ࡣࠊs=1.5 ࡛࠶ࡿ [14]ࠋࡓࡔࡋࠊཝᐦࡣࠊs=1.5 ࡣ༢⣧࡞❧ ᪉ᬗ⣔࠾ࡅࡿィ⟬್࡛࠶ࡿࠋࡋࡋ࡞ࡀ ࡽࠊs=1.5 ࡢ್ࡣࠊ⤒㦂ⓗศᏊᛶ⤖ᬗࢆྵ ࡴᵝࠎ࡞❧᪉ᬗ⣔௨እࡢ≀㉁࡛ࡶ⏝࠸ࡽࢀ ࡚࠾ࡾࠊ⮬ᕫ᮰⦡ບ㉳ᏊࡢᏳᐃᛶࡢド᫂ 㐺⏝ࡉࢀ࡚࠸ࡿ[12]ࠋE-Ga2O3 ࠾࠸࡚ࠊᅗ 3 ࡛ᘧ(2)ࢆ⏝࠸࡚ࢫࢸ࣮ࣉࢿࢫಀᩘࡢ ᗘ౫ᏑᛶࡢࣇࢵࢸࣥࢢࡼࡾᚓࡽࢀࡓV ࡣ 0.28 ࡛࠶ࡿࡓࡵࠊg=5.4 ồࡲࡗࡓࠋࡇ ࢀࡣ 1 ࡼࡾ༑ศࡁ࡞್࡛࠶ࡿࠋࡍ࡞ࢃ ࡕࠊE-Ga2O3 ࠾࠸࡚ࠊ⮬ᕫ᮰⦡ບ㉳Ꮚࡣࠊ ⮬⏤ບ㉳Ꮚẚ࡚Ᏻᐃ࡛࠶ࡿࡇࡀࠊᐇ (2) ࡛࠼ࡽࢀࡿࠋࡇࡇ࡛ࠊEph ࡣບ㉳Ꮚ┦ స⏝ࡍࡿ⌧㇟ㄽⓗ࡞ࣇ࢛ࣀ࢚ࣥࢿࣝࢠ̿ࠊ Vࡣ㧗 ࠾ࡅࡿࢫࢸ࣮ࣉࢿࢫಀᩘࡢ ᮰್࡛࠶ࡿࠋᅗ 3 ࡢᐇ⥺ࡣࠊᘧ(2)ࢆ⏝࠸ࡓ ࣇࢵࢸࣥࢢ⤖ᯝࢆ♧ࡋ࡚࠸ࡿࠋࣇࢵ ࢸࣥࢢࣃ࣓࣮ࣛࢱࡣࠊࡑࢀࡒࢀࠊV=0.28, Eph=31 meV ồࡲࡗࡓࠋ Schreiber ㇏ἑࡼࡾሗ࿌ࡉࢀࡓ⌮ㄽ ᇶ࡙ࡃ[14]ࠊ⮬ᕫ᮰⦡ບ㉳ᏊࡢᏳᐃᛶࢆ♧ ࡍບ㉳Ꮚ̿᱁Ꮚ┦స⏝ᐃᩘࡣ௨ୗࡢᘧ࡛ 269 ࡞ࡿࠋᚑࡗ࡚ࠊE-Ga2O3 ࡛ࡣࠊ⮬ᕫ᮰⦡ບ㉳ ᏊࡀᏳᐃ࡛࠶ࡿࡇࡀ᫂ࡽ࡞ࡗࡓࠋࡉ ࡽࠊ⮬ᕫ᮰⦡ບ㉳ᏊᙧᡂࡢᏳᐃ࢚ࢿࣝ ࢠ̿ࡣࠊ0.68 eV ホ౯ࡉࢀࠊࡇࢀࡣ⮬ᕫ᮰ ⦡ṇᏍᙧᡂࡢᏳᐃ࢚ࢿࣝࢠ࣮ࡢィ⟬್ 0.53 eV[13]ࡰ୍⮴ࡋࡓࠋࡑࢀࡺ࠼ࠊ ࡁ࡞ࢫࢺ࣮ࢡࢫࢩࣇࢺࢆకࡗࡓࣈ࣮ࣟࢻ࡞ Ⓨගᖏࡣࠊ᫂☜⮬ᕫ᮰⦡ບ㉳Ꮚࡽࡢࡶ ࡢ࡛࠶ࡿࡇ࡛࠶ࡿ⤖ㄽ࡙ࡅࡽࢀࡿࠋ 㦂ⓗド᫂ࡉࢀࡓࠋ ㇏ἑࡼࡿ⮬ᕫ᮰⦡ບ㉳Ꮚࣔࢹࣝ(ᅗ 4) ᇶ࡙ࡃ[16]ࠊᅗ 2 ♧ࡋࡓ࣮ࣂࢵࢡࢸ ࣝࡢ᮰࢚ࢿࣝࢠ̿ࡣ E0=Ea㸫Bࠊ⮬ᕫ᮰ ⦡ບ㉳ᏊࡽࡢⓎග࢚ࢿࣝࢠ̿ࡣ Ea㸫2ELR ࡛࠼ࡽࢀࡿࠋ࡞࠾ࠊEa ࡣບ㉳Ꮚࣂࣥࢻࡢ ୰ᚰ࢚ࢿࣝࢠ࣮࡛࠶ࡿࠋࡺ࠼ࠊࢫࢺ࣮ࢡ ࢫࢩࣇࢺ Es ࡣ௨ୗࡢᘧ࡛࠼ࡽࢀࡿࠋ (5) Es 2 E LR B ᪤㏙ࡓࡼ࠺ࠊᅗ 1 ࡽࠊࢫࢺ࣮ࢡࢫ ࢩࣇࢺࡣࠊES=1.5 eV ࡛࠶ࡿࠋg=5.4ࠊEs=1.5 eVࠊཬࡧࠊᘧ(3)(5)ࡽࠊ᱁Ꮚ⦆࢚ࢿࣝ ࢠ̿ELR=0.83 eVࠊບ㉳Ꮚࣂࣥࢻ༙ᖜ B=0.15 eV ぢ✚ࡶࡽࢀࡓࠋ ᭱ᚋࠊ⮬ᕫ᮰⦡ບ㉳ᏊࡢᏳᐃ࢚ࢿࣝ ࢠ̿ࡘ࠸࡚㆟ㄽࡍࡿࠋᩥ⊩[16]ᇶ࡙ࡃࠊ Ᏻᐃ࢚ࢿࣝࢠ̿EST ࡣᅗ 4 ࡼࡾࠊ௨ୗࡢᘧ ࡛࠼ࡽࢀࡿࠋ EST E LR B (6) ᘧ(6)ࢆ⏝࠸࡚ࠊᐇ㦂್ࡽ EST=0.68 eV ồࡲࡗࡓࠋᩥ⊩[13]࡛ࠊE-Ga2O3 ࠾ࡅࡿ⮬ ᕫ᮰⦡ṇᏍᙧᡂࡢᏳᐃ࢚ࢿࣝࢠ̿ࡣ➨୍ ཎ⌮ⓗ࡞⌮ㄽィ⟬ࡼࡾࠊEST=0.53 eV ồ ࡵࡽࢀ࡚࠸ࡿࠋ⮬ᕫ᮰⦡ບ㉳Ꮚࡢᒁᅾ୰ᚰ ࡣ⮬ᕫ᮰⦡ṇᏍ࡛࠶ࡿࡇࡽࠊ⮬ᕫ᮰⦡ ບ㉳ᏊᙧᡂࡢᏳᐃᛶࡣࠊ⮬ᕫ᮰⦡ṇᏍ ࡢᏳᐃ࢚ࢿࣝࢠ̿ࡼࡗ࡚Ỵᐃࡉࢀࡿࠋ ࡇࡢゎᯒࡽᚓࡽࢀࡓ EST=0.68 eV ࡣࠊ⮬ᕫ ᮰⦡ṇᏍࡢᏳᐃ࢚ࢿࣝࢠ̿ࡢィ⟬್ EST=0.53 eV Ⰻ࠸୍⮴ࢆ♧ࡋ࡚࠸ࡿࠋࡇࡢ ⤖ᯝࡣࠊ⮬ᕫ᮰⦡ບ㉳ᏊᙧᡂࡢᏳᐃᛶ㛵 ࡍࡿࡇࢀࡽࡢゎᯒࡣጇᙜ࡛࠶ࡿࡇࢆ ࡅ࡚࠸ࡿࠋ 4. ࡲࡵ E-Ga2O3 ༢⤖ᬗ࠾ࡅࡿ⮬ᕫ᮰⦡ບ㉳Ꮚࡢ Ᏻᐃᛶࡢゎ᫂ࢆ┠ⓗࡋ࡚◊✲ࢆ⾜ࡗࡓࠋ Schreiber ㇏ἑࡼࡿࠊບ㉳Ꮚ̿᱁Ꮚ┦ స⏝ࡢ⌮ㄽᇶ࡙࠸࡚[14]ࠊ࣮ࣂࢵࢡࢸ ࣝࡢ ᗘ౫Ꮡᛶࡘ࠸࡚ゎᯒࢆ⾜ࡗࡓࠋࡑ ࡢ⤖ᯝࠊບ㉳Ꮚ̿᱁Ꮚ┦స⏝ᐃᩘ g=5.4 ồࡲࡗࡓࠋ୍⯡ⓗ g>1 ࡢሙྜࠊ⮬⏤ບ ㉳Ꮚẚࠊ⮬ᕫ᮰⦡ບ㉳Ꮚࡢ᪉ࡀᏳᐃ 270 ཧ⪃ᩥ⊩ [1] H. 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