Search

The control over impurities like hydrogen and oxygen is of key importance in nitride-based semiconducting due to their unrivaled applicability in optoelectronics and high power/high frequency electronics. Therefore, it is desirable to continue the research on its diffusion and segregation in semiconductor materials. In this work, we report on a first observation on hydrogen outdiffusion from bulk crystalline gallium nitride. The extent of the hydrogen diffusion is established by secondary ion mass spectrometry. Analysis of characteristic hydrogen profile in GaN grown using ammonothermal method, led to the determination of the hydrogen diffusion coefficient at the temperature of 1045C - a standard growth temperature for HVPE (halide vapor phase epitaxy) method., Comment: 8 pages, 2 figures, regular paper

Diffusion mechanism of beryllium in gallium nitride was investigated by analyzing temperature-dependent diffusion profiles from an infinite source. Beryllium atoms were implanted into a high structural quality gallium nitride layer crystallized by halide vapor phase epitaxy on an ammonothermal gallium nitride substrate. Post-implantation annealing was performed at different temperatures, between 1000{\deg}C and 1400{\deg}C, under high nitrogen pressure. Beryllium profiles were analyzed in the as-implanted and annealed samples by secondary ion mass spectrometry. It was shown that the diffusion of the dopant results from the combination of two mechanisms: rapid interstitial and slow interstitial-substitutional diffusion. The pre-exponential factor as well as activation energy for both diffusion paths were determined. Moreover, from the characteristic features of beryllium depth profiles, the formation energies of gallium vacancy and beryllium in interstitial position were calculated and compared to the theoretical values., Comment: 16 pages, 6 figures, 1 table, 4 equations

The control over the structural homogeneity is of paramount importance for ternary nitride compounds - the second most important semiconducting material-class after Si, due to its unrivalled applicability in optoelectronics, and high power/high frequency electronics. Therefore it is timely to investigate possible mechanisms influencing the crystallographic constitution of the material. In this work the diffusion mechanism of manganese in gallium nitride is investigated in two types of epilayers: Mn implanted metalorganic vapour phase epitaxy grown GaN and (Ga,Mn)N solid solution grown by molecular beam epitaxy. The extent of the Mn diffusion is established by secondary ion mass spectrometry. Analysis of the Mn profiles in the implanted samples in the frame of the infinite source diffusion led to the establishment for the first time of the pre-exponential factor DO = 2x10-4 cm2/s and diffusion activation energy EA = 1.8 eV describing the diffusion coefficient of Mn in GaN. Modelling of the out-diffusion of Mn from (Ga,Mn)N layers based on these values in turn allows to provide an explanation of the origin of the ubiquitously observed near-the-surface sizable depletion of Mn in (Ga,Mn)N, resulting from the blocking of the Mn out-diffusion by Mn-oxide and the correspondingly formed space-charge layer on the surface., Comment: Journal of Alloys and Compounds 2018

The topological crystalline insulator tin telluride is known to host superconductivity when doped with indium (Sn$_{1-x}$In$_{x}$Te), and for low indium contents ($x=0.04$) it is known that the topological surface states are preserved. Here we present the growth, characterization and angle resolved photoemission spectroscopy analysis of samples with much heavier In doping (up to $x\approx0.4$), a regime where the superconducting temperature is increased nearly fourfold. We demonstrate that despite strong p-type doping, Dirac-like surface states persist.

We present a unified interpretation of experimentally observed magnetic circular dichroism (MCD) in the ferromagnetic semiconductor (Ga,Mn)As, based on theoretical arguments, which demonstrates that MCD in this material arises primarily from a difference in the density of spin-up and spin-down states in the valence band brought about by the presence of the Mn impurity band, rather than being primarily due to the Zeeman splitting of electronic states., Comment: 4+ pages, 4 figures

Structural and magnetic properties of GaAs thin films with embedded MnAs nanoclusters were investigated as function of the annealing temperature and layers composition. The presence of two kinds of nanoclusters with different dimensions and structure were detected. The fraction of Mn atoms in each kind of cluster was estimated from the extended X-ray absorption fine structure analysis. This analysis ruled out the possibility of the existence of nanoclusters containing a hypothetic MnAs cubic compound - only (Mn,Ga)As cubic clusters were detected. Change of the layer strain from the compressive to tensile was related to the fraction of zinc blende and hexagonal inclusions. Thus the zinc blende inclusions introduce much larger strain than hexagonal ones. The explanation of observed thermal induced strain changes of the layers from the compressive to tensile is proposed. The magnetic properties of the samples were consistent with structural study results. Their showed that in sample containing solely cubic (Mn,Ga)As inclusions Mn ions inside the inclusions are still ferromagnetically coupled, even at room temperature. This fact can be explained by existence in these clusters of GaMnAs solid solution with content of Mn higher than 15 % as was found in theoretical calculations., Comment: 12 pages, 16 figures, 4 tables

p-type doping of molecular-beam-epitaxy grown layers of the diluted magnetic semiconductor Zn(1-x)MnxTe is achieved by using an active nitrogen cell. The strong interaction between the localized Mn spins and the holes deeply modifies the transport properties (metal-insulator transition, spin-dependent Hall effect). In spite of the weak localization of the carriers at low temperature, the holes clearly induce a ferromagnetic interaction between the localized spins, which is discussed as a function of Mn content and hole concentration., Comment: 3 figures Ninth International Conference on II-VI Compounds, Kyoto, Japan, november 1999