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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]

The partially-relaxed heterogeneous GaInNAs layers grown on GaAs substrate by atmospheric pressure vapor phase epitaxy (AP-MOVPE) were investigated by transmission electron microscopy (TEM) and atomic force microscopy (AFM). The planar-view TEM image shows a regular 2D network of misfit dislocations oriented in two orthogonal 〈1 1 0〉 crystallographic directions at the (0 0 1) layer interface. Moreover, the cross-sectional view TEM image reveals InAs-rich and V-shaped precipitates in the near surface region of the GaInNAs epitaxial layer. The resultant undulating surface morphology, known as a cross-hatch pattern, is formed as observed by AFM. The numerical analysis of the AFM image of the GaInNAs layer surface with the well-defined cross-hatch morphology enabled us to determine a lower bound of actual density of misfit dislocations. However, a close correspondence between the asymmetric distribution of interfacial misfit dislocations and undulating surface morphology is observed. [ABSTRACT FROM AUTHOR]

The structural investigations of thick undoped GaInNAs/GaAs heterostructures grown by atmospheric pressure vapor phase epitaxy (AP-MOVPE) have been performed by transmission electron microscopy (TEM) and X-ray diffraction (XRD) techniques. The cross-sectional view TEM images revealed plainly heterogeneous layer structure, consisting of a few sublayers with different indium and nitrogen contents. On the other hand, planar-view TEM images revealed 2D network of misfit dislocations oriented in two orthogonal 〈110〉 crystallographic directions at the (001) sublayer interface. Moreover, the XRD measurements provide information about gradient profiles of indium and nitrogen contents, as well as distinct anisotropy of strain relaxation in GaInNAs epitaxial layer, evoked by the asymmetry in formation of interfacial misfit dislocation. The obtained results were exploited to calculate the band structure diagram of the investigated GaInNAs/GaAs heterostructure and mean values of the lattice parameters of the distorted epitaxial layer unit cell, respectively. [ABSTRACT FROM AUTHOR]

Deep level transient spectroscopy was used to investigate deep-level defects in (Ga,In)(N,As)/GaAs triple quantum well structures grown by atmospheric pressure metalorganic vapor phase epitaxy with different indium and nitrogen contents and annealed in rapid thermal annealing system. A combination of electron traps that disappear or remain on annealing and a new hole trap that appears on annealing were detected. The revealed electron traps were attributed to N-related complexes or GaAs host-related native point defects. Moreover, it was suggested that the new hole trap observed in the annealed GaAsN/GaAs triple quantum well structure together with the dominant electron trap can act as generation-recombination center responsible for the observed a very poor optical quality among all the investigated multi-quantum well structures. [ABSTRACT FROM AUTHOR]

Electrical properties of commercial silicon carbide (SiC) Schottky rectifiers are investigated through the measurement and analysis of the forward current-voltage (I-V) (C-V) characteristics in a large temperature range. Some of devices show distinct discrepancies in specific ranges of their electrical characteristics, especially the excess current dominates at voltage <1 V and temperature <300 K. Standard deep level transient spectroscopy (DLTS) revealed the presence of a single deep-level defect with activation energy of about 0.3 eV, exhibiting the features characteristic for extended defects (e.g. dislocations), such as logarithmic capture kinetics. Furthermore, high-resolution Laplace DLTS showed that this deep level consists actually of three closely spaced levels with activation energies ranging from about 0.26 eV to 0.29 eV. A strong correlation between these two techniques implies that the revealed trap level is due to extended defects surrounded by point traps or clusters of defects. On the basis of obtained specific features of the deep-level defect, it was proposed that this defect is arguably responsible for the observed Schottky barrier inhomogeneities. [ABSTRACT FROM AUTHOR]

Highlights: [•] DLTS technique was used to study deep electron traps in 4H-SiC JBS rectifiers. [•] Five single-peak and one dominant double-peak deep electron traps were revealed. [•] The traps were attributed to impurity-related or intrinsic defects in n-type 4H-SiC epilayers. [•] The dominant deep electron trap at EC –0.68eV was attributed to Z 1/Z 2 defect. [ABSTRACT FROM AUTHOR]

Abstract: The relaxation process in InGaAs/GaAs heterostructures with a small lattice mismatch (less than 1%), grown by metalorganic vapour-phase epitaxy (MOVPE), has been investigated by means of high-resolution X-ray diffraction (HR-XRD). Transmission electron microscopy (TEM) revealed a two-dimensional (2D) network of 60° misfit dislocations formed at the (001) interface in the two orthogonal 〈110〉 crystallographic directions. The structural analysis by X-ray diffractometry was performed with the samples oriented either in the [1¯10] or the [110] perpendicular directions, using reciprocal lattice mapping. The observed anisotropic-strain relaxation, related to the asymmetry in the formation of α and β misfit dislocations along [1¯10] and [110] directions, respectively, causes distortion of the epilayer unit cell and lowers its symmetry to orthorhombic. [Copyright &y& Elsevier]

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]

Abstract: The electrical and optical properties of the lattice-mismatched InGaAs/GaAs heterostructures, with partial strain relaxation, were studied by deep level transient spectroscopy (DLTS) and photoreflectance (PR) spectroscopy, respectively. In the samples one of deep electron traps, revealed by DLTS, was ascribed to misfit dislocations at the interface, for which capture kinetics, concentration depth profiles and the type of electronic states have been specified. Room temperature PR spectroscopy was used for analysing the effect of residual strain on the optical response from the samples, i.e. interband transitions and the valence band splitting. [Copyright &y& Elsevier]

Abstract: Electronic properties of strain-induced dislocations in partially relaxed InGaAs/GaAs heterostructures with a small lattice mismatch have been studied by means of deep-level transient spectroscopy (DLTS). DLTS investigations carried out with Schottky contacts revealed one deep electron trap, at about EC −0.57eV. The trap has been attributed to electron states associated with α misfit dislocations lying at the interface between the epilayer and the substrate. Thorough studies including DLTS-line shape, DLTS-line behaviour analysis as well as capture kinetics and deep profile measurements made possible to specify the type of electronic states associated with dislocations. We relate the electron trap to “localized” states at misfit dislocations. [Copyright &y& Elsevier]

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]