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Materials Science in Electronics devices
- Semiconductor devices -
2015 Yutaka Oyama
oyama@material.tohoku.ac.jp
http://www.material.tohoku.ac.jp/~denko/lab.html
Contents
・ Material issue of semiconductor devices and fabrication process
• Schematics of thin film growth (Molecular Layer Epitaxy, etc.)
・ Ultra fast and high frequency semiconductor electronic and photonic devices -1
• Ultra fast and high frequency semiconductor electronic and photonic devices -2
・ Crystal growth and semiconductor device epitaxy
・ Device grade evaluation of semiconductor crystals
UV
Blue
Green
Yellow
Orange
red
wavelength
color
Energy[eV] wavelength frequency
infrared
UV
X-ray
photonConductionband
Valenceband
Conductionband
Valenceband
photon
Direct transition
Electron/hole and photon interaction
High emission efficiency
Indirect transition
Electron/hole and lattice vibration (phonon) interaction
Low emission efficiency
lattice vibration (phonon)
発光色
発光領域となるp型半導体の、伝導帯と価電子帯のエネルギー差(バンドギャップ)が大きいほど、電子が伝導帯から価電子帯へ落ちるときに発せられる光のエネルギーは大きなものとなる。また、光の色は波長によって変化する。また波長は光のエネルギーが大きいほど短いものとなる。そのため、光の色は半導体のバンドギャップの大きさによって左右されることになる。バンドギャップは材料によってほぼ決まるので、放出される光の色は材料によって決まるといえる。下の表に、材料と光の色との関係を示した。
色 材料 material ピーク波長 wavelength接合構造
青
InGaN 450 量子井戸
ZnCdSe 489 ダブルへテロ
緑
ZnTeSe 512 ダブルへテロ
GaP 555 ホモ接合
黄
AGaInP 570 ダブルへテロ
InGaN 590 量子井戸
赤
AlGaAs 660 ダブルへテロ
GaP(Zn-0) 700 ホモ接合
赤外
GaAs(Si) 980 ホモ接合
InGaAsP 1300 量子井戸
0.92
6.895.87 6.48
0.18
1.35
0
0.8
1.6
2.4
5.6 6.0 6.45.2
0.5
1.0
2.0
5.0
Lattice constant [Å]
Bandgap
[eV
]w
avele
ngth
[μm
]
GaP
GaAs
InP GaSb
InSb
0.92
6.895.87 6.48
0.18
1.35
0
0.8
1.6
2.4
5.6 6.0 6.45.2
0.5
1.0
2.0
5.0
Lattice constant [Å]
Bandgap
[eV
]w
avele
ngth
[μm
]
GaP
GaAs
InP GaSb
InSb
半導体結晶の格子定数と禁制帯幅Lattice constants & band gap energies
c
hE
electron charge q is 1.602x10-19 [C],
Plank constant h is 6.626×10-34[J・s],
light velocity in vacuum c is
3×108[m/s].
主な光デバイス半導体材料の格子定数とEg(=色)
Lattice constant [A]
Band gap energy[eV]
Lattice fitting is one of the most important factor for high quality crystal growth
Lattice mismatch will introduce serious crystalline defects into device structure.
Trend of LED luminescent efficiency
~mm-10mm
~100mm
(THz wave)
GaP
LiNbO
DAST
GaSe
ZnGeP
PbTe
PbSnTe
HgCdTe
医療応用生体分子スペクトロスコピー
励起・治療
リモートセンシング(Nox、CO2・・)非石英系ファイバー通信(超低損失)
IR
(infrared)
Visible light
UV light
発光デバイス発光ダイオード(=PNダイオード)
Light emitting diode (LED) = PN diode structure
Minority carrier diffusion length of electron in p-type region is longer than that of hole in n-region,Thus light emission will enhanced at the p-side interface region of pnjunction.
発光ダイオードの光損失Reduction of emitted light intensity inside the semiconductors
Light absorption within semi.
Fresnel reflection at the semi. Air interface due to refractive index difference
Total reflection phenomenon at the semi/air interface
同種接合ホモ接合
異種接合ヘテロ接合
量子井戸構造
発光効率向上のための接合構造 Junction structures for improved luminescence
efficiency
電流狭さく構造光閉じ込め効果(屈折率大<屈折率小)
Confinement of
Current & light
Homo junction
Hetero junction
発光ダイオード(LED)の高効率化
Double hetero junction structure
Enhancement of light emission efficiency of LED
Carrier confinement by potential barrierLight confinement by high refractive index of active region
No absorption of light within cladding layer of AlGaAs
発光デバイス半導体レーザ
Spontaneous emission (natural) Stimulated emission
LASER (Light Amplification by Stimulated Emission of Radiation
ConductionBand
Valenceband
自然放出と誘導放出
Spontaneous emission & Stimulated emission
Phase of light is randomized not single frequency (wavelength)
Phase of light is single (coherent) Single frequency light
Spontaneous emission
Stimulated emission
光学遷移確率
Optical transition probability
Spontaneous emission
Stimulated emission
Inter band absorption
半導体レーザの共振器構造
Cavity of semiconductor laser
Total reflectionMirror
Partial reflectionMirror
Lasing media(lasing material)
Excitation light
半導体レーザの構造=LEDとほとんど同じ
LD structure is almost the same as that of LED
Cladding layer
Cladding layer
Active layer
Ex.cleaving
光(増幅)利得 g
電子の反転分布(負の温度)
Condition for light amplification
Normal semi. condition Abnormal (inversion distribution of electrons)
Inversion distribution=Negative temperature FD distribution
半導体レーザの光スペクトラム
Typical emission spectra of LD
半導体レーザのビームプロファイル
Light beam profile from LD
レーザビームの近視野像と遠視野像Near field and far field beam profiles of LD
電流ー光室力特性(しきい値電流)
Threshold current for lasing
低次元構造(量子井戸構造など)を用いたLD
Low dimensional structures for LDValence band is degenerated(light hole and heavy hole)Effective mass difference
ストライプ構造のレーザ
Stripe laser diode (edge emitting diode)
半導体レーザの構造例 (edge emitting laser)
Some tricky structure of LDApplication of amphoteric impurity site occupation difference between (111) sidewall and (100) surface
面発光レーザ vertical cavity laser
分布帰還形レーザ(Distributed FeedBack laser) :DFB laser波長選択性 波長可変半導体レーザ (tunable laser)
白色発光ダイオード
White light LED
長い
Operation principle of white light LED
Yellow light is emitted from the absorbed blue
or UV from LED, then the white light is
generated by the mixture of yellow and blue.
Very interesting history of LASER invention
1917 Albert Einstein: Zur Quantentheorie der Strahlung(放射の量子論について)1928 Rudolf W. Ladenburg: stimulated emission & negative absorption1939 Valentin A. Fabrikant: prediction of light amplification1947 Wilis Ram R. C. Retherford: first appearance of stimulated emission (hydrogen emission)1950 Alfred Castlel: proposal of light pumping method1953 Charles Towns, James P. Gordon(Student), Herbert J. Zeiger: Microwave amplification by solid (MASER)1953 Von Neuman: idea of semi. Laser by private letters to friends1957 Yasushi Watanabe, Jun-ichi Nishizawa (TOHOKU Univ.): JP patent of semi. LASER(特公昭35-13787)
1957 James P. Gordon: idea of open light cavity (exp. Notes) evidence for patent !
1959 April James P. Gordon: USP of LASER but canceled1960 Theodore Harold Maiman: realization of LASER (AlO3:Cr LASER)1962 Robert N. Hall: GaAs IR LASER at 77K1970 Iwao Hayashi, Morton Panish: RT LD using double hetero junction1987 James P. Gordon was formally assigned as LASER inventor by US court
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