arXiv subjects

Robert Czernecki

Publications and source records attributed to Robert Czernecki.

2 recordsLinked to original sources

arXiv2026

Role of quasi-Fermi levels in Si- and Mg-related optical absorption in nitride laser diodes (LDs): material context

Optical absorption and reabsorption of light emitted from active regions in nitride laser diodes (LDs) have been shown to reduce the light extraction efficiency of these devices. It was proven that the presence of Si and Mg may considerably increase the optical absorption. This effect is much stronger in the high-energy (short-wavelength) range of the spectrum. The absorption increase is directly related to the ionization of the Si donor and Mg acceptor levels, which are controlled by the electron and hole quasi-Fermi levels. It is shown that the absorption may be increased because of the higher ionization of Mg caused by the compensation in the p-type region and the high ionization of Si in the n-type region. It was explained theoretically why optical efficiency is increased by removal of doping in waveguides. It was also shown that good material quality leads to a low absorption level, especially in the Mg-doped p-type part of the device.

cond-mat.mtrl-sci↗

arXiv2011

Structures built by steps of evaporated crystal surface Monte Carlo simulations and experimental data for GaN epi layers

We present Monte Carlo simulation data obtained for the annealed surface GaN(0001) and compare them with the experimental data. High temperature particle evaporation is a part of substrate preparation processes before epitaxy. The ideal surface ordering expected after such heating is a pattern of parallel, equally distanced steps. It appears however, that different types of step structures emerge at high temperatures. We show how the creation of characteristic patterns depends on the temperature and the annealing time. The first pattern is created for a very short evaporation time and consists of rough steps. The second pattern built by curly steps is characteristic for longer evaporation times and lower temperatures. The third pattern, in which steps merge together creating bunches of steps happens for the long enough time. At higher temperatures, bunches of steps bend into the wavy-like structures.

cond-mat.stat-mech↗