Many THz applications require detection of sub-picosecond THz pulses. Electronic detectors, in particular, can address this challenge. We report on the detection of sub-picosecond THz pulses generated by a large-area interdigitated photoconductive antenna using a AlGaN/GaN high electron mobility transistor with integrated bow-tie antenna. We demonstrate that the detector's photoresponse is linear in a wide range of gate bias voltages regarding the available THz radiation power with peak power levels of a few hundreds of milliwatts. We apply an autocorrelation technique to investigate the spectral response of our detector within a bandwidth exceeding 1 THz. We observe an unexpected frequency roll-off of responsivity, which can not be predicted using a framework of standard distributed transmission line theory. However, we show that the data can be understood if one accounts for only partial plasmon screening by the gate electrode, so that the results adhere simply to the distributed resistive mixing approximation, whereby the device suffers from the observed roll-off. This indicates, that for novel detectors and radiation sources, which intend to utilize plasma waves, it is important to ensure efficient screening by the gate electrode.

The operation dynamics of the capacitor-type and PIN diode type detectors based on GaN have been simulated using the dynamic and drift-diffusion models. The drift-diffusion current simulations have been implemented by employing the software package Synopsys TCAD Sentaurus. The monopolar and bipolar drift regimes have been analyzed by using dynamic models based on the Shockley-Ramo theorem. The carrier multiplication processes determined by impact ionization have been considered in order to compensate carrier lifetime reduction due to introduction of radiation defects into GaN detector material.

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Plasma formation and extraction processes in silicon n + np + TRAPATT (TRApped Plasma Avalanche Triggered Transit) diodes were simulated. The drift-diffusion model was chosen for the simulation of the processes. This model is adequate for diodes under consideration with a total thickness of 6.5 µm. Two approximations of carrier diffusion coefficient dependence on the electric field above 20 kV/cm were used. A strong dependence of plasma density and oscillation period on n + n junction steepness was found in the case of a constant electron diffusion coefficient in the electric field range above 20 kV/cm. This behaviour depends on the impact ionization model in silicon. Two models were used. In one of them we included drift and diffusion current in the impact ionisation process. In the other model we included only the drift current in the impact ionisation process. In the second case the influence of the n + n junction steepness on the plasma formation process is much stronger. In the diodes with a highly abrupt n + n junction the TRAPATT mode is impossible. These results explain our experiments on TRAPATT diodes with an abrupt n + n junction.

Dynamic characteristics in the case of a large signal of partly gain-coupled multiple-quantum-well InGaAsP-InP distributed feedback (GC DFB) laser diodes have been investigated. Simple rate equations for carrier and photon densities were taken. A possibility to simulate the modulation characteristics of GC DFB lasers using these equations has been shown. Chirp and optical power pulses obtained by time-resolved frequency chirp measurements were compared with modelled ones.