We report on a novel concept for THz photomixers with high conversion efficiency up to several THz. In contrast to the conventional pin photomixer we can overcome the trade-off between either optimizing transit-time or RC-roll-off. Using quasi-ballistic transport in nano-pin-diodes the transport path can be optimized regarding both path length and transit time. Independently, the capacitance can be kept small by using a sufficiently large number of optimized nano-pin-diodes in series. The concept is presented in detail and first experimental results are reported which corroborate our theoretical expectations.

Conventional semiconductor‐based photomixers are limited by the carrier transit‐time‐roll‐off and the RC‐roll‐off of the device‐capacitance. We have developed a THz‐photomixer which can overcome both limitations and proves far superior to a conventional pin‐photomixer. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

We report on a novel concept for THz-photomixers based on quasi-ballistic transport in an asymmetric nipnipdoping-superlattice. Due to tansport-optimized i-layers the emitted powers are not transit-time-limited up to 1 T Hz. Furthermore the capacitance and hence the RC-roll-off is minimized by increasing the number of pin-periods. The frequencydependence of the nipnip-emitter proofs to be superior to corresponding pin-photomixers.

We investigate a THz-photomixer based on quasi-ballistic transport in an asymmetric n-i-p-n superlattice. The measured frequency roll-off is due to the device RC time constant alone whilst the transit-time limitation is overcome in this device, Measured power levels compare well with those from standard LT-GaAs photomixers.