Strain-Engineered Ge/SiGe Resonant Tunneling Diodes for Silicon-Based Terahertz Emitters

We present a comprehensive theoretical study of n-type Ge/SiGe resonant tunneling diodes integrated on Si substrates, aimed at developing CMOS-compatible terahertz oscillators. Leveraging non-equilibrium Green's function simulations combined with semi-analytical modeling, we investigate the influence of band structure engineering, strain, and heterostructure composition on device performance. Optimal double-barrier quantum well profiles are identified within experimentally feasible constraints, highlighting a trade-off between the device current density and the current peak-to-valley ratio (PVR) in the negative differential resistance (NDR) region of the J-V characteristic. Optimized designs feature PVRs of up to similar to 10 at low current densities or, alternatively, higher current densities of up to 100 kA/cm2 accompanied by lower PVR values. Predicted cut-off frequencies exceed 1 THz, with output powers on the order of tenths of milliwatts. Furthermore, a drift-based model highlights the importance of lateral bias uniformity in mesa devices, setting critical design limits for stable negative differential resistance behavior. These results indicate the potential of Ge/SiGe resonant tunneling diodes as a viable route toward silicon-integrated THz electronic sources, bridging the gap between III-V and group-IV semiconductor platforms.