Abstract
Plasma waves in semiconductor gated 2-D systems can be used to efficiently detect Terahertz (THz) electromagnetic radiation. This work reports on the response of a strained-Si Modulation-doped Field-Effect Transistor (MODFET) under front and back sub-THz illumination. The response of the MODFET has been characterized using a two-tones solid-state continuous wave source at 0.15 and 0.30 THz. The DC drain-to-source voltage of 500-nm gate length transistors transducing the sub-THz radiation (photovoltaic mode) exhibited a non-resonant response in agreement with literature results. Two configurations of the illumination were investigated: (i) front side illumination in which the transistor was shined on its top side, and (ii) back illumination side where the device received the sub-THz radiation on its bottom side, i.e., on the Si substrate. Under excitation at 0.15 THz clear evidence of the coupling of terahertz radiation by the bonding wires was found, this coupling leads to a stronger response under front illumination than under back illumination. When the radiation is shifted to 0.3 THz, as a result of a lesser efficient coupling of the EM radiation through the bonding wires, the response under front illumination was considerably weakened while it was strengthened under back illumination. Electromagnetic simulations explained this behavior as the magnitude of the induced electric field in the channel of the MODFET was considerably stronger under back illumination.
Highlights
Over the last two decades, the progress in new semiconductor materials and devices has fostered the research of room-temperature Terahertz (THz) detectors [1]
The portion of the electromagnetic (EM) spectrum located between the infrared region and the RF/microwaves one is commonly known as the Terahertz or submillimeter region and THz radiation is referred as T-rays
The present paper reports on the use of field-effect transistors (FETs) based on the SiGe/Si/SiGe double-heterojunction as sub-THz plasma-waves detectors
Summary
Over the last two decades, the progress in new semiconductor materials and devices has fostered the research of room-temperature Terahertz (THz) detectors [1]. At the beginning of the nineties, Dyakonov and Shur [12,13] presented a ground-breaking work that proposed and demonstrated the ability of sub-micron FETs (Field-Effect Transistors) to detect terahertz radiation. Electron plasma in the channel of FETs. While the proposal of Dyakonov and Shur was a theoretical work, in the course of the following years the detection of sub-terahertz radiation based on plasma waves was experimentally demonstrated using different types of FETs such as silicon MOSFETs (Metal-Oxide-Semiconductor Field-Effect Transistor) [14], strained-Si MODFETs Terahertz detectors based on the properties of the 2D electron plasmas in FET channels perform direct detection of the incoming THz radiation using a frequency down-conversion technique. The present paper reports on the use of field-effect transistors (FETs) based on the SiGe/Si/SiGe double-heterojunction as sub-THz plasma-waves detectors. The study focuses on the differences of the photovoltaic response when the device receives front (the one commonly used) and back THz illumination. 3D FDTD (Finite-difference time-domain) simulations are performed to explain the results obtained in measurements at 0.3 THz
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