Resonant Tunnelling Diodes for next-generation THz systems

Resonant tunnelling diodes (RTDs) are a strong candidate for future wireless communications in the THz spectrum (sub-millimetre waves), offering compact, room-temperature operation with the potential to exceed the bit transfer rate mandated by the 12G-SDI standard, using a single wireless link. A free-space RTD emitter operating at 353GHz is described. The fabrication process consists of a dual-pass I-line photolithography & etch technique using an air bridge, allowing low resistivity ohmic contacts, and accurate control of desired device area. With extrinsic circuit elements taken into account, the intrinsic semiconductor efficiency is analysed to investigate structural improvements for radiative efficiency. Such optimised structures are presented, and then characterised after being epitaxially grown with commercially viable metal-organic vapour phase epitaxy (MOVPE) reactors. A combination of low temperature photoluminescence spectroscopy, X-Ray diffractometry, and transmission electron microscopy attest the quality of the new material. We end with a suggestion for the next steps to exceed technological readiness levels of 8, and use monolithic RTD emitters as components in new systems.