State-of-the-art SIMS, XRR and AFM have been used to determine the effect of oxidation temperature on the inhomogeneity of chemical composition and density in nanometric SiO₂ films grown on n-type 4H-SiC by thermal oxidation in dry oxygen.

The formation of intrinsic point defects in the N-sublattice of semi-insulating Mg-doped GaN crystals grown by the ammonothermal method (SI AT GaN:Mg) was investigated for the first time. The grown-in defects produced by the displacement of nitrogen atoms were experimentally observed as deep traps revealed by the Laplace transform photoinduced transient spectroscopy in the compensated p-type crystals with the Mg concentrations of 6 × 10¹⁸ and 2 × 10¹⁹ cm⁻³ and resistivities of ~10¹¹ Ωcm and ~10⁶ Ωcm, respectively. In both kinds of materials, three closely located traps with activation energies of 430, 450, and 460 meV were revealed. The traps, whose concentrations in the stronger-doped material were found to be significantly higher, are assigned to the (3+/+) and (2+/+) transition levels of nitrogen vacancies as well as to the (2+/+) level of nitrogen split interstitials, respectively. In the material with the lower Mg concentration, a middle-gap trap with the activation energy of 1870 meV was found to be predominant. The results are confirmed and quantitatively described by temperature-dependent Hall effect measurements. The mechanism of nitrogen atom displacement due to the local strain field arising in SI AT GaN:Mg is proposed and the effect of the Mg concentration on the charge compensation is discussed.

Laplace photoinduced transient spectroscopy has been applied to determine the electronic properties and concentrations of deep traps in high purity n-type silicon irradiated with high fluences of 23-MeV protons. From the temperature dependence of thermal emission rates of excess charge carriers obtained by the analysis of the photocurrent relaxation waveforms measured at temperatures of 30–320 K, eight deep traps with activation energies ranging from 255 to 559 meV have been resolved. The dependence of these trap’s concentrations on the proton fluence are demonstrated for the fluence values ranging from 1 × 10¹⁴ to 5 × 10¹⁵ n_eq/cm². In comparison to the previously reported results of theoretical and experimental studies on the electronic properties of small vacancy clusters in irradiated silicon, we tentatively attribute four detected traps with activation energies of 255, 367, 405, and 512 meV to the energy levels related to the 2−/− charge state changes of divacancy (V₂), trivacancy (V₃), tetravacancy (V₄), and pentavacancy (V₅), respectively. Simultaneously, we propose the attribution of four deep traps with higher activation energies of 415, 456, 526, and 559 meV to the energy levels related to the −/0 charge state changes of these small vacancy clusters, respectively.

The properties and concentrations of deep-level defects induced by implantations of Si and Mg ions into unintentionally doped (UID) epitaxial GaN have been revealed by using the Laplace-transform photoinduced transient spectroscopy (LPITS) and molecular dynamics (MD) calculations. The material lattice damage, produced by the Si ions implanted at room temperature in the single process at the energies of 200 and 340 keV, is compared with that produced by the Mg ions implanted in the similar process at the energies of 150, 210, and 270 keV. The LPITS results indicate that the same deep traps with the activation energies of 396, 512, 531, 587, 635, and 736 meV are present in the tail regions of the semi-insulating Si- and Mg-implanted films. It is argued that the predominant implantation-induced point defects in the tail region of the Si-implanted films are nitrogen vacancies, whose concentration is 7.7 × 10¹⁷ cm⁻³. In the Mg-implanted films, the predominant implantation-induced point defects are gallium interstitials, whose concentration is 1.2 × 1 0¹⁸ cm⁻³.

For the first time, the Z₁ and Z₂ defects with closely spaced energy levels having negative-U properties are revealed in high-purity semi-insulating (HPSI) 4H-SiC using Laplace-transform photoinduced transient spectroscopy (LPITS). In this material, after switching off the optical trap-filling pulse, either the one-electron or the two-electron thermally stimulated emission from these defects is observed at temperatures 300–400 K. It is found that the former corresponds to the Z₁^0/+ and Z₂^0/+ transitions with the activation energies of 514 and 432 meV, respectively, and the latter is associated with the Z₁^−/+ and Z₂^−/+ transitions with the activation energies of 592 meV and 650 meV, respectively. The Z₁ and Z₂ defect concentrations are found to increase from 2.1 × 10¹³ to 2.2 × 10¹⁴ cm⁻³ and from 1.2 × 10¹³ to 2.7 × 10¹⁴ cm⁻³, respectively, after the heat treatment of HPSI 4H-SiC samples at 1400 °C for 3 h in Ar ambience. Using the electrical trap-filling pulse, only the thermal two-electron emission from each defect was observed in the epitaxial 4H-SiC through Laplace-transform deep level transient spectroscopy (LDLTS). The activation energies for this process from the Z₁ and Z₂ defects are 587 and 645 meV, respectively, and the defect concentrations are found to be 6.03 × 10¹¹ and 2.64 × 10¹² cm⁻³, respectively. It is postulated that the Z₁ and Z₂ defects are the nearest-neighbor divacancies involving the carbon and silicon vacancies located at mixed, hexagonal (h), and quasi-cubic (k) lattice sites.