NASA Logo

NTRS

NTRS - NASA Technical Reports Server

Back to Results
Embedded Coplanar Strips Traveling-Wave PhotomixersThe electric field distribution in photomixers with electrodes deposited on the surface has already been calculated. It was shown that the strength of the electric field diminishes rapidly with depth. It was argued that the resulting reduction of the effective interaction volume of the device lowers the optical-to-heterodyne conversion. In this paper, we will present the results of our investigation on the influence of the electrode placement on the performance of photomixers. We have fabricated and measured traveling-wave photomixer devices which have both embedded and surface electrodes - the nominal spacing between the electrodes was 2 micrometers. Devices were made using either low-temperature-grown (LTG)-GaAs or ErAs:GaAs as the photoconductive material. The dark current, photocurrent, and radio frequency (RF) emission were measured at nominally 1 THz. The experimental data show a surprising difference in the behavior of ErAs:GaAs devices when the electrodes are embedded. A factor of two increase in RF radiation is observed for electric fields < 20 kV/cm. No such improvement was observed for the LTG-GaAs devices. We argue that the distinctive behavior of the two photoconductive materials is due to differences in the crystal structure - LTG-GaAs is isotropic, while ErAs:GaAs is uniaxial. We find that the carrier mobility in-plane (parallel) to the ErAs layers in the ErAs:GaAs superlattice is larger than orthogonal to these layers. The data indicate that carrier velocity overshoot is responsible for the excess radiation produced for the embedded electrode ErAs:GaAs devices.
Document ID
20020038932
Document Type
Conference Paper
Authors
Wyss, R. A.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Lee, T.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Pearson, J. C.
(Jet Propulsion Lab., California Inst. of Tech. Pasadena, CA United States)
Matsuura, S.
(California Inst. of Tech. Pasadena, CA United States)
Blake, G. A.
(California Inst. of Tech. Pasadena, CA United States)
Kadow, C.
(California Univ. Santa Barbara, CA United States)
Gossard, A. C.
(California Univ. Santa Barbara, CA United States)
Date Acquired
August 20, 2013
Publication Date
December 1, 2001
Publication Information
Publication: Proceedings of the Twenlfth International Symposium on Space Terahertz Technology
Subject Category
Electronics And Electrical Engineering
Distribution Limits
Public
Copyright
Work of the US Gov. Public Use Permitted.

Related Records

IDRelationTitle20020038920Analytic PrimaryProceedings of the Twelfth International Symposium on Space Terahertz Technology
No Preview Available