This work presents a detailed investigation of strain engineering in a Ge-source double-gate tunnel field-effect transistor (Ge-DG-TFET) employing strained Si/SiGe/Si heterostructure channel. Initially, the performance of a conventional Si-channel device is compared with that of a strained (Si/Si\(_{0.7}\)Ge\(_{0.3}\)/Si) channel to examine the influence of strain on device characteristics. The strained channel demonstrates a noticeable improvement, with the ON-state current increasing from 1.74 to 2.13 \(\hbox {mA/}\upmu \hbox {m}\), threshold voltage reducing from 0.251 to 0.243 V, and \(\hbox {f}_t\)/\(\hbox {f}_{max}\) from 3.02 GHz / 0.40 MHz to 3.48 GHz / 0.43 MHz. Subsequently, the effect of increasing germanium mole fraction in the channel, corresponding to enhanced strain, is systematically analyzed by varying the SiGe composition up to Si/Si\(_{0.3}\hbox {Ge}_{0.7}\)/Si. With increasing strain in the channel, the ON-state current improves significantly to 3.32 mA/\(\upmu \text {m}\), while the transconductance increases from 8.22 \(\hbox {mS/}\upmu \hbox {m}\) to 11.24 \(\hbox {mS/}\upmu \hbox {m}\). The RF performance also shows substantial enhancement, with the cutoff frequency increasing from 3.48 THz to 4.35 THz and the maximum oscillation frequency improving from 0.43 to 0.54 MHz. These results confirm that strain-engineered Si/SiGe/Si channels effectively enhances both DC, AC/RF and linearity performance of Ge-DG-TFETs, making them suitable for low-power and terahertz frequency applications.
