Summary
International Symposium on Antennas and Propagation
2009
Session Number:3D1
Session:
Number:3D1-3
A Numerical Study of THz Emission Properties of Arsenic-ion-implanted GaAs Based Photoconductive Antennas
Phumin Kirawanich,
pp.991-994
Publication Date:2009/10/21
Online ISSN:2188-5079
Summary:
Radiation from far-infrared region of the electromagnetic spectrum is of great importance for time-resolved terahertz (THz) spectroscopy and imaging to provide a non-invasive method for identifying the compositions of non-conducting objects. Applications of sub-millimetre wave technology include medical imaging, bioscience, surveillance and security screening, and pharmaceutical science. The tool generating terahertz wave is usually an antenna based on the photoconductive (PC) switch, which consists of a semiconductor bridging the gap in a transmission line structure deposited on the semiconductor substrate [1]. An ultra short optical pulse focused onto the gap between two voltage-biased electrodes initiates the transient response of the photoconductive switch. The induced photocurrent then radiates into free space proportional to its time derivative. Low temperature grown GaAs (LT-GaAs) is preferred as the substrate of PC antennas due to a short carrier lifetime and reasonably good mobility that can produce ultra-short current pulses of less than picoseconds FWHM [2]. An alternative arsenic-rich material known as arsenic-ion-implanted GaAs (GaAs:As+ ) has recently been reported [3]. The GaAs:As+ exhibits structural, electrical, and ultrafast optoelectronic characteristics similar to those of LT-GaAs due to the presence of the implantation-induced defects. The advantage of GaAs:As+ over the LT-GaAs is the substrate preparation by ion implantation, which can be controlled more precisely than the epitaxial growth temperature of LT-GaAs. Thus, GaAs:As+ is expected to work as an efficient substrate for the PC antennas. For that reason, gaining an insight of the device performance through a preliminary numerical design is essential. The limitation of commercially available software is lacking of integrated interactions between the emitter and the semiconductor. In this paper we report on a numerical analysis of an ultrashort pulse emission by taking into account such interactions by incorporating between Maxwell’s curl and semiconductor carrier transport equations. We have organized the paper as follows. The details of PC antenna model and computation algorithm are described in Section 2. Section 3 discusses the numerical results. This work concludes in Section 4.