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YONSEI UNIVERSITY
YONSEI UNIVERSITY
UTC-PD
(Unitraveling-carrier photodiode)
2015.04.10
김창훈
ITO, Hiroshi, et al. High-speed and high-output
InP-InGaAs unitraveling-carrier photodiodes.
Selected Topics in Quantum Electronics, IEEE
Journal of, 2004, 10.4: 709-727.
YONSEI UNIVERSITY
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Contents(UTC-PD)
2
UTC-PD operation(UTC-PD vs pin-PD)
Digital, Analog application
Device characteristics
Conclusion
YONSEI UNIVERSITY
UTC-PD operation (UTC-PD vs pin-PD)
3
< Pin-PD band diagram >
< UTC-PD band diagram >
UTC-PD characteristic
Use of electrons as the only active carriers
Active part : absorption layer(p-type)
+ carrier collection layer(lightly n-type]
Diffusion block layer : unidirectional motion of electrons
Band gap grading : reduce electron traveling time
Pin-PD characteristic
Both electrons and holes contribute to the response
Carrier velocity : hole < electron
Response : hole transport dominant
p-type
n- type
YONSEI UNIVERSITY
UTC-PD operation (UTC-PD vs pin-PD)
4
UTC-PD advantage 1 : high speed
Electron diffusion time dominant
Large minority mobility of electron
in p-InGaAs
And design thin absorption layer
without sacrificing the RC charging
time
< Charge distribution, field, and band bending at high carrier injection levels >
Photocurrent ↑
→ Mobile charge density ↑
→ Modulate field profile
p-type
Electron velocity overshoot
YONSEI UNIVERSITY
UTC-PD operation (UTC-PD vs pin-PD)
5
UTC-PD advantage 2 : higher saturation current
electron velocity overshoot >> hole velocity (pin-PD]
Electric field ↓
→ carrier velocity ↓
→ charge storage ↑
→ current saturation
< Pin-PD >
< UTC-PD >
YONSEI UNIVERSITY
Device characteristics
6
< pulse photoresponse of Pin-PD > < pulse photoresponse of UTC-PD >
Basic photoresponse
Slow tail caused by slow hole transport
Low saturation output
Slow response by space charge effect UTC-PD advantage 3 : wide linearity
High speed (advantage 1]
Wide linearity
YONSEI UNIVERSITY
Device characteristics
7
Bandwidth
< UTC-PD frequency response >
UTC-PD advantage 1 : high speed Large minority mobility of electron