Title

A terahertz radiation detection system design and device modeling

Date of Completion

January 2003

Keywords

Engineering, Electronics and Electrical

Degree

Ph.D.

Abstract

A novel terahertz (THz) radiation detection system was introduced based on the BICFET device of the Inversion Channel Technology (ICT). It can work at room temperature with attractive responsivity and noise performance properties. The hot electron effect due to the interaction between the electron ensemble in the channel and the radiation is formulated based on the simplified hydrodynamic theory. It is proven that the maximum detectable radiation frequency fRF is determined by the 2DEG momentum relaxation time and the IF cutoff frequency fIF is determined by the 2DEG energy relaxation time. The detection of THz radiation utilizing 2DEG is implemented by the BICFET. The basic mechanism is that the electron temperature increase in the channel will result in the increase of thermionic emission from the quantum well and hence the increase of collector current. The equilibrium, DC, AC and noise characteristics of the BICFET are modeled, from which the responsivity and NEP of the BICFET Hot Electron Bolometer are derived. The radiation coupling with integrated antennas is studied by simulation using Momentum software and C programs. The radiation pattern of the planar log-periodic antenna on a semi-infinite semiconductor substrate is first simulated, and the effect of an extended hemispherical lens attached at the back of the antenna substrate is then calculated using techniques of ray-tracing and field integration. The fabricated process is briefly described and the testing techniques for various aspects of the system are discussed. This dissertation also dealt with experimental small signal modeling of the ICT HFET, which has the same generic epi-structure as BICFET. The parasitic and intrinsic parameters of the small signal model are characterized by measuring S parameters of the device under different biasing conditions. Finally, a dynamic model of SCH semiconductor lasers is developed. A novel method based on quasi Fermi levels for electrons and holes was used to develop the theory. The model was verified by comparing with the experimental data in the literature. ^