We present a non-local history-dependent model for impact ionization gain and noise in avalanche photodiodes (APDs) especially suited for staircase APDs. The model uses a simple energy balance equation to define effective electric fields valid also in the presence of band discontinuities which are then used to express the ionization coefficients. The model parameters have been calibrated against literature data for gain and noise in GaAs and AlxGa1−xAs (x = 0.2, 0.6, 0.8) p-in diodes. Application to experimental data for gain and noise in heterojunction and staircase SAM-APDs is reported to demonstrate the ability of the model in describing complex APD structures. It is found that, in spite of conduction band discontinuities being much larger than valence band ones, hole impact ionization contributes a significant degradation of the noise metrics in GaAs/AlGaAs staircase APDs. These non-trivial insights demonstrate the usefulness of the model to steer device design and optimization.

In the present study is shown a novel vacuum‐based technique that enables production of hard polymeric nanocomposite coatings with metal (Cu) nanoparticles. This method is based on the use of gas aggregation source (GAS) of Cu nanoparticles and plasma‐enhanced chemical vapour deposition of a‐C:H matrix that was deposited in a mixture of Ar and n‐hexane on the substrates placed on the powered RF electrode. This approach makes it possible to control independently both the properties of the matrix by variation of the applied RF power and the amount of incorporated Cu nanoparticles that may be adjusted by operational parameters of the GAS. Characterisation of the films in terms of their chemical composition, morphology, optical and mechanical properties is described here alongside with description of Cu nanoparticles production using GAS with variable aggregation length.

This work focuses on the development and the characterization of avalanche photodiodes with separated absorption and multiplication regions grown by molecular beam epitaxy. The i-GaAs absorption region is separated from the multiplication region by a p-doped layer of carbon atoms, which ensures that after applying a reverse bias, the vast majority of the potential drops in the multiplication region. Therein, thin layers of AlGaAs and GaAs alternate periodically in a socalled staircase structure to create a periodic modulation of the band gap, which under bias enables a well-defined charge multiplication and results in a low multiplication noise. The influence of the concentration of carbon atoms in the p-doped layer on the device characteristics was investigated and experimental data are presented together with simulation results.