**3. THz setup**

Static (DC) and THz measurements were carried out at room temperature. On-wafer, DC measurements of drain-to-source current versus drain-to-source and gate-to-source bias voltages were done using a Cascade 11000B probe station and an Agilent B1500A semiconductor parameter analyzer. **Figure 3** shows a photograph with a schematic of the experimental setup used for the terahertz characterization of the strained-Si MODFETs. A solid-state harmonic generator THz source based on a dielectric resonator oscillator (DRO) at 12 GHz and electronic Room-Temperature Terahertz Detection and Imaging by Using Strained-Silicon MODFETs http://dx.doi.org/10.5772/intechopen.76290 59

**Figure 3.** Photograph of the experimental setup and schematic description of the THz (blue) and red laser (red line) beams.

multiplication to reach 0.15 THz with a power of 3 mW and 0.3 THz with a power of 6 mW was used to excite the transistors. The output power was measured close to the source using a highly sensitive calibrated pyroelectric detector. The incoming THz radiation was modulated by a mechanical chopper between 0.233 and 5 kHz, collimated and focused by an indium tin oxide (ITO) mirror and off-axis parabolic and plane mirrors. A red LED (or laser) was used for the alignment of the THz beams.

The photo-induced drain-to-source voltage, ΔU, was measured using a lock-in technique. Finally, a X-Y stage was used to generate pixel-by-pixel THz images.
