In the case of molecular beam epitaxy (MBE), the Mg acceptors are electrically active in the as‐grown material and a priori no additional annealing procedure is necessary. However, there are still some peculiarities in the electrical properties of ammonia‐process grown GaN:Mg and some annealing effect can be observed. Additionally, the character of weak temperature dependence in the vicinity of room temperature suggests that to describe the conduction process an additional conduction channel not related to the free carriers in the valence band must be taken into account. For these reasons, this article presents the results of low‐temperature resistivity and Hall Effect studies of Mg‐doped, ammonia‐process‐grown GaN. The studied samples are grown on low‐temperature buffers of GaN deposited on a sapphire substrate. High‐temperature annealing process (≈800 K) is carried out for all of them. The temperature dependences of the electrical transport properties before and after the annealing procedure are especially investigated at temperatures ranging from 10 up to 300 K. It is found that the low temperatures transport properties are sensitive to the annealing procedure and to describe the observed effects the hopping phenomena must be taken into account.

The π-conjugated polymer polydiphenylbutadiyne was prepared at the nanoscale confined inside the 1.2 nm 1-D pores of the aluminophosphate AlPO4-54. Molten 1,4-diphenyl-1,3-dibutadiyne (DPB) was inserted in the pores of AlPO4-54 at pressures below 0.3 GPa as confirmed by X-ray diffraction. Heating to 190 °C under a pressure of 0.4 GPa induced polymerization of DPB in the pores. Infrared microscopy indicates full polymerization in the pores and the presence of characteristic saturated C–H defects common to other nanostructured PDPB materials exhibiting important photocatalytic properties. This nanostructured PDPB confined in the hygroscopic AlPO4-54 host could be of interest for applications in gas sensing, photocatalysis and hydrogen generation.

This paper presents low-temperature measurements of magnetoresistivity in heavily doped n-type GaN grown by basic GaN growth technologies: molecular beam epitaxy, metal-organic vapor phase epitaxy, halide vapor phase epitaxy and ammonothermal. Additionally, GaN crys-tallized by High Nitrogen Pressure Solution method was also examined. It was found that all the samples under study exhibit negative magnetoresistivity at low temperature (10 K < T < 50 K) and for some samples this effect is observed up to 100 K. This negative magnetoresistivity effect is analyzed in the frame of the weak localization phenomena in the case of three-dimensional electron gas in a highly doped semiconductor. This analysis allows to determine the phasing coherence time τφ for heavily doped n-type GaN. The obtained τφ value is proportional to T-1.34, indicating that the electron–electron interaction is the main dephasing mechanism for the free carriers.

This work explores a contactless resistivity measurement method dedicated to the study of quantum phenomena. The method belongs to the category of RadioFrequency (RF) eddy currents and is based on a gradiometric inductive coil.

This paper presents a comparative study of electron transport phenomena in n-type gallium nitride strongly doped, above the Mott transition, with silicon and germanium. The samples under study were grown by molecular beam epitaxy, metal-organic vapor phase epitaxy and halide vapor phase epitaxy. The temperature dependence of resistivity and Hall Effect was investigated at temperatures ranging from 10 K up to 650 K. The measurements at sub-room temperatures allow the study of scattering mechanisms related to extrinsic material properties. The observed temperature dependences of the electrical transport properties were analyzed in the frame of the model taking into account a typical scattering mechanism and degree of degeneracy of free carrier electron gas. The limitations of the applied models will be presented.