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We present resonant-tunnelling-diode (RTD) oscillators operating at the fundamental frequency of 1111 GHz. We show that our RTDs and RTD oscillators have much room for further improvement of their parameters and for further increase of their operating frequencies. The operating frequencies of several THz should be achievable with RTD oscillators. Our study also shows that operation of RTDs beyond the relaxation-time limit at THz frequencies should be possible. RTD oscillators under study are extremely compact (less than a square millimeter) room-temperature sources of coherent cw THz radiation. Such sources should enable plenty of real-world THz applications.

The formation of precipitates after an annealing process in low-temperature-grown GaAs0.6Sb0.4 is observed. We use high-resolution transmission electron microscopy for a detailed structure investigation and demonstrate the functionality of the material, which has a band gap of 0.86 eV, for ultrafast optical switches. The average diameter of the clusters is 5.7 nm in the bulk region, while larger clusters are observed near the interface to a 1.3% lattice mismatched Al0.77In0.23As buffer layer. After an annealing treatment, the sheet resistance is increased by five orders of magnitude to 1.7×108Ω/sq, which is sufficiently high to enable Auston switch operation. We report terahertz (THz) emission from the material measured in a THz time-domain spectroscopy setup. THz generation is demonstrated by using a six interdigital finger metal-semiconductor-metal structure at the feed-point of a log-periodic antenna.

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