We demonstrate an “island” design of on-chip slot-antenna resonant-tunneling-diode (RTD) oscillators, where the contact n++ layer is removed everywhere except for a small island under the RTD. At frequencies around 2 THz, this design leads to a significant reduction (by a factor of ≈ 2) in the total Ohmic losses at the conducting surfaces of the slot antenna. With this design, we achieved the highest radiated power for RTD oscillators in the frequency range of 1.6-1.74 THz with around 2.2 μW at the fundamental frequency of 1.74 THz. Theoretical analysis of the oscillators indicates that with the utilized RTD design, the operating frequencies beyond 2 THz should be reached if the RTD contact resistance is reduced to 1-1.5 Ω μ m2
