Unitraveling-Carrier Photodiodes for Terahertz Applications

Device design for unitraveling-carrier photodiodes (UTC-PDs) and their derivative structures is reconsidered from the point of view of terahertz (THz) applications. A key design procedure for maximizing their bandwidth is optimization by incorporating hybrid absorbers. The effect of quasi-field in p...

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Bibliographic Details
Published in:IEEE journal of selected topics in quantum electronics 2014-11, Vol.20 (6), p.79-88
Main Authors: Ishibashi, Tadao, Muramoto, Yoshifumi, Yoshimatsu, Toshihide, Ito, Hiroshi
Format: Article
Language:English
Subjects:
Antennas
Bandwidth
Bias
Derivatives
Diodes
Electric potential
Indium gallium arsenide
Optical switches
Optimization
Photodiodes
Space charge
Transient analysis
Voltage
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Summary:Device design for unitraveling-carrier photodiodes (UTC-PDs) and their derivative structures is reconsidered from the point of view of terahertz (THz) applications. A key design procedure for maximizing their bandwidth is optimization by incorporating hybrid absorbers. The effect of quasi-field in p-type absorber is carefully examined. It has been shown that the initial velocity transient must be taken into account to evaluate the effective average velocity. Photomixers integrating a hybrid-absorber UTC-PD and a bow-tie antenna were fabricated and characterized. THz-wave generation by the photomixers in a frequency range of up to around 2.5 THz was confirmed. The observed THz-wave output exhibits significant changes with bias voltage, where the decrease in the output with increasing negative bias voltage is more pronounced at higher frequencies. This output behavior is due to the change in electron velocity in the diode depletion layer associated with the overshoot effect. From the dependence of the output power on frequency, effective electron velocity is found to be as high as 6 \times 10^{7} cm/s at optimum bias voltage of -0.4 V.
ISSN:1077-260X
1558-4542
DOI:10.1109/JSTQE.2014.2336537