Search

Several deep level defects were observed by conventional deep level transient spectroscopy (DLTS) and high-resolution Laplace DLTS (LDLTS) in n-type 4H-SiC junction barrier Schottky diodes. We have shown that the broad DLTS peak labeled Z1/2 has, in fact, two components, Z1 and Z2, with activation enthalpies for electron emission of 0.63 eV and 0.68 eV, respectively. The reorientation process between these two components was observed. A combination of double-correlated DLTS and LDLTS demonstrated an anomalous reduction of the emission rate and an increase of the activation enthalpy of Z2 with an increase of the reverse bias applied to the diode. The possible explanation of this phenomenon could be correlated with a tensile stress in epitaxial SiC layers. The results observed are discussed in the frame of the model that correlates Z1 and Z2 with carbon vacancies (VC), located at hexagonal (h) and cubic (k) lattice sites, respectively. We also discussed the origin of other traps E0–E5 with particular emphasis on a N-related shallow donor level located at 0.04 eV below the conduction band, which has never been previously reported by DLTS studies. [ABSTRACT FROM AUTHOR]

Deep-level defects were investigated by deep level transient spectroscopy on the as-grown and annealed GaNAs layers of various nitrogen (N) contents. The unintentionally doped (uid) GaNAs layers were grown by metalorganic vapor phase epitaxy with N=1.4%, 2.0%, 2.2%, and 2.4% on GaAs substrate. The possible origin and evolution of the deep-level defects upon annealing were analyzed with the use of the GaNAs band gap diagram concept [Kudrawiec et al., Appl. Phys. Lett. 101, 082109 (2012)], which assumes that the activation energy of donor traps decreases with N-related downward shift of the conduction band. On the basis of this diagram and in comparison with previous results, the N-related traps were associated with (N-As)As or (N-N)As split interstitials. It was also proposed that one of the electron traps and the hole trap, lying at the same level position in the bandgap of the annealed uid-GaNAs layers, can both act as one generation-recombination center partially responsible for poor optical properties of this alloy. [ABSTRACT FROM AUTHOR]

Deep level traps in as-grown and annealed n-GaNAs layers (doped with Si) of various nitrogen concentrations (N=0.2%, 0.4%, 0.8%, and 1.2%) were investigated by deep level transient spectroscopy. In addition, optical properties of GaNAs layers were studied by photoluminescence and contactless electroreflectance. The identification of N- and host-related traps has been performed on the basis of band gap diagram [Kudrawiec, Appl. Phys. Lett. 101, 082109 (2012)], which assumes that the activation energy of electron traps of the same microscopic nature decreases with the rise of nitrogen concentration in accordance with the N-related shift of the conduction band towards trap levels. The application of this diagram has allowed to investigate the evolution of donor traps in GaNAs upon annealing. In general, it was observed that the concentration of N- and host-related traps decreases after annealing and PL improves very significantly. However, it was also observed that some traps are generated due to annealing. It explains why the annealing conditions have to be carefully optimized for this material system. [ABSTRACT FROM AUTHOR]

Partially relaxed InGaAs/GaAs heterostructures with a small lattice mismatch (less than 1%), grown by metalorganic vapour-phase epitaxy have been studied by the transmission electron microscopy, atomic force microscopy as well as X-ray diffractometry. A regular network of 60° misfit dislocations formed at the (001) interface in two orthogonal <110> crystallographic directions has been revealed. A close correspondence between distribution of the interfacial misfit dislocations and undulating surface morphology in the form of a characteristic cross-hatch pattern has been observed. The structural analysis applied for the samples oriented either in [11̅10] or [110] perpendicular directions, using reciprocal lattice mapping, revealed anisotropic strain relaxation, related to the asymmetry in the formation of α and β misfit dislocations along these both directions, respectively. [ABSTRACT FROM AUTHOR]

Convenient and simple criteria are proposed enabling one to distinguish between deep level point and extended defects (e.g. dislocations) in DLTS measurements. The approach is based on earlier reports of several authors and on our own experiences in the field of DLTS data analysis for III-V semiconductors. It consists of standard DLTS measurements widened by line shape and line behaviour analysis, as well as capture kinetics measurements. In the first part, the paper presents a survey of the literature on the analysis of DLTS signals originating from dislocations. In the second part, selected experimental data on distinguishing and identifying deep point and extended defects, in GaAs/GaAs and InGaAs/GaAs heterostructures, are presented. [ABSTRACT FROM AUTHOR]

Deep-level defects in n-type GaAs 1-x Bi x having 0 ≤ x ≤ 0.023 grown on GaAs by molecular beam epitaxy at substrate temperature of 378 °C have been injvestigated by deep level transient spectroscopy. The optical properties of the layers have been studied by contactless electroreflectance and photoluminescence. We find that incorporating Bi suppresses the formation of GaAs-like electron traps, thus reducing the total trap concentration in dilute GaAsBi layers by over two orders of magnitude compared to GaAs grown under the same conditions. In order to distinguish between Bi- and host-related traps and to identify their possible origin, we used the GaAsBi band gap diagram to correlate their activation energies in samples with different Bi contents. This approach was recently successfully applied for the identification of electron traps in n-type GaAs 1-x N x and assumes that the activation energy of electron traps decreases with the Bi (or N)-related downward shift of the conduction band. On the basis of this diagram and under the support of recent theoretical calculations, at least two Bi-related traps were revealed and associated with Bi pair defects, i.e. (V Ga +Bi Ga ) -/2- and (As Ga +Bi Ga ) 0/1- . In the present work it is shown that these defects also influence the photoluminescence properties of GaAsBi alloys.