Transcript 下載/瀏覽

Temperature and current dependences of
electroluminescence from InGaN/GaN
multiple quantum wells
Jiunn-ChyiLee , Ya-FenWu , Yi-PingWang , Tzer-EnNee
YS
outline
•
•
•
•
•
Introduction
Experiment
Results and discussion
Conclusion
References
Introduction
• The report on a detailed investigation of the EL spectra from
InGaN/GaN MQWs as a function of temperature and
injection current level to understand the mechanism of
carriers transferring in the structure.
• The anomalous S-shaped temperature behavior of the EL
peak energy and the W-shaped temperature behavior of the
EL full-width at half- maximum (FWHM) are well explained
by the localized carrier hopping and thermalization process.
Experiment
Chip size:350*350μm2
Ni-Au
100nm-Mg-doped p-GaN-1019cm-3
2nm-In0.18 Ga0.82 N/11nm-GaN MQW 5 periods
3μm-Si-doped n-GaN-5*1018cm-3
20nm-GaN buffer
Sapphire
Ti/Al/Ti/Au
Results and discussion
Fig. 1. EL spectra of
InGaN/GaN MQWs
in the temperature
range from 20 to
300K. The driving
current is 20mA.
Fig. 2. Temperature dependence of(a)peak position. (b)FWHM of EL spectra from the
InGaN/GaN MQWs with different values of current.The solid lines are fitting curves
based on the band-tail model with fitting parameters listed in Table1.
（1）
（2）
Table1
Fitting parameters used in the band-tail mode lfo rcalculating the localization effect in
InGaN/GaN MQWs at various injection currents
帶尾能態(band-tail )
Fig. 2. Temperature dependence of(a)peak position. (b)FWHM of EL spectra from the
InGaN/GaN MQWs with different values of current.The solid lines are fitting curves based
on the band-tail model with fitting parameters listed in Table1.
Fig. 3. The dependence of the spectral peak position on injection current in the
InGaN/GaN MQWs at different temperatures between 20 and 300K.
Fig. 4. EL external quantum efficiency of InGaN/GaN MQWs as a function of temperature
in the injection current range from 10 to 100 mA.
Conclusion
• It is observed that the EL efficiency is strongly
dependent on temperature and injection current.
• The variation of EL efficiency with increasing
temperatures and increasing injection currents
is consistent with the investigation of heating
effect and localization effect.
References
• J. Bai, T. Wang, S. Sakai, J. Appl. Phys. 88 (2000) 4729.
• P.G. Eliseev, P.Perlin, J.Lee, M.Osin´ ski, Appl.Phys.Lett.
71(1997)569.
• S. Dhar, U. Jahn, O. Brandt, P. Waltereit, K.H. Ploog, Appl. Phys.
Lett. 81 (2002) 673.
2.79
10mA
60mA
100mA
2.78
Photon Energy(eV)
2.77
2.76
2.75
2.74
2.73
2.72
2.71
2.70
2.69
2.68
2.67
0
50
100
150
200
Temperature(k)
250
300
2.70
Photon Energy (eV)
2.69
2.68
2.67
2.66
10mA
60mA
100mA
2.65
2.64
0
50
100
150
200
Temperature (K)
250
300
帶尾能態(band-tail ):
對於施體(donor)密度超過價帶之能態密度(density of state)的n 型
半導體，不但電子開始填至導帶，更導致能帶結構變形，例如形
成非拋物線(non-parabolic)形式的導帶，以及在能隙周圍形成侷
限載子之帶尾能態(bandtail state)[16]。由於氮化銦奈米結構的背
景電子濃度(約1018cm-3)遠大於光激載子密度(約1016cm-3)，主
要的光學複合過程為填至費米能階(Fermi level)的電子以及侷限
在價帶頂端帶尾能態的光激電洞(photoexcited hole)，因此非對稱
的發光譜線形狀主要是由電子分布所決定。當背景電子濃度降低
時不但譜峰位置和電子分布的費米能階位置隨之往低能量移動，
譜線的半高全寬也隨之降低。