Terahertz integrated transmission line sensors using a bonded epitaxial GaAs layer on silicon substrates

We have developed a novel process of transmission line type terahertz (THz) devices for biological sensing. A low-temperature-grown (LT) GaAs layer side is bonded onto silicon substrates using Au-Sn solder, then the GaAs substrate is removed by selective wet etching. Photoconductive switch elements for generating and detecting THz signals are fabricated on the transferred LT-GaAs layer. This process results in robust integrated devices against biological solutions. Sequential measurement of THz time domain spectroscopy is available for biological molecules such as DNA samples. We observe clear difference in delay time shifts according to change of quantity and the state of applied molecules.