Resonant Tunnelling Diodes for next generation THz systems

Abstract

Resonant tunnelling diodes (RTDs) are a strong candidate for future wireless communications in the THz spectrum (sub-millimetre waves), offering compact, roomtemperature 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.

Non-destructive characterization of thin layer resonant tunneling diodes

“…In the previous work, 21 we have highlighted that PL is a powerful technique for estimation of the n + doping level using the Moss-Burstein effect; variation of the doping across the wafer, confirmed with Hall effect measurements, and LT-PL mapping was performed. 40 Equally important, PL showed variations of the LM-InGaAs mole fraction at less than 0.6%, observation sustained with the good fit around the Bragg peak of Fig. 4.…”

“…Lower resolution data for structure A were presented recently. 40 The best fit to this structure has suggested an In 0.87 Ga 0.13 As QW and a bottom and top AlAs barrier of 1.3 and 1.1 nm, respectively (both active and dummy regions). The QW width was found to be within the design tolerance at 3.9 nm, and the top cap was also found to be indium-rich x = 0.87, and slightly thinner, at 7.8 nm.…”

Quantum dot photoconductive antenna-based compact setups for terahertz spectroscopy and imaging

“…7 Microwave avalanche diodes and Gunn diodes operate very efficiently at frequencies from 10 to 300 GHz, but with frequency increase up to and beyond 1 THz their efficiency drops very quickly. 8 Thus, especially for spectroscopy and ultra-fast process studies, pulsed and continuous wave optically pumped sources are of most interest.…”