5-THz bandwidth from a GaAs-on-silicon photoconductive receiver

Abstract

We demonstrate that GaAs grown by molecular beam epitaxy on silicon has ideal characteristics for THz receiver applications. The lattice mismatch between silicon and GaAs causes a disordered growth of GaAs, reducing the carrier lifetime to 1.8 ps. This is similar to the characteristics observed in low temperature grown GaAs. Furthermore, the high resistivity silicon substrate has a very low absorption and dispersion in the far infrared. This makes it an ideal material in THz system applications, and we show that a maximum frequency of 5 THz and a sixfold increase in sensitivity can be obtained using a GaAs-on-silicon based THz detector.

Far-Infrared Dielectric Properties of Polar Liquids Probed by Femtosecond Terahertz Pulse Spectroscopy

“…It is important to note that the spectral resolution of the spectrometer is dictated by the distance scanned by the optical delay line and is not limited by the short duration of the fs THz pulse . In the present experimental setup, the response of the SOS receiver (including absorption by the sapphire substrate) dictates the upper limit of the useful frequency range; other workers have reported significant improvements in measured bandwidth upon switching to receivers with faster response characteristics . The accurate measurement of linear optical constants, however, requires only that the receiver responds linearly at any given frequency and is independent of any additional knowledge of the frequency dependence of that response.…”

Exploring Dynamics in the Far-Infrared with Terahertz Spectroscopy

“…This type of source can provide a bandwidth as high as 5 THz. 26 Because it is a resonant excitation method, it is limited not only by the excitation laser pulse width, but also the response time of the material. This type of source is typically used with oscillator-only, i.e., nonamplified, systems, and there has only been a small amount of time-resolved work using this type of THz pulse generator.…”

Optimization of photoconducting receivers for THz spectroscopy

“…Various materials and methods of construction have since been explored with the aim of improving sensitivity or bandwidth. These include flip-chip bonding of SOS receivers on to lower dispersion Si substrates [7], the epitaxial growth of Si on high resistivity Si substrates with an intervening layer of silicon dioxide [8], the growth of LT GaAs epilayers [9] and GaAs on Si epitaxy [10]. Receiver optimization involves achieving the best compromise between bandwidth, sensitivity and noise in the choice of material, antenna design and optics.…”