Auger recombination (AR) being electron-hole annihilation with energy-momentum transfer to another carrier is believed to speed up in materials with small band gap. We theoretically show that this rule is violated in gapless three-dimensional materials with ultra-relativistic electron-hole dispersion, Weyl semimetals (WSM). Namely, AR is prohibited by energy-momentum conservation laws in prototypical WSM with a single Weyl node, even in the presence of anisotropy and tilt. In real multi-node WSM, the geometric dissimilarity of nodal dispersions enables weak inter-node AR, which is further suppressed by strong screening due to large number of nodes. While partial AR rates between the nodes of the same node group are mutually equal, the inter-group processes are non-reciprocal, so that one of groups is geometrically protected from AR. This geometrical protection prolongs AR lifetime up to two orders of magnitude, to the level of nanoseconds.
Current-voltage characteristics and quantum efficiency dependence on injected current for blue light emitting diodes with different nanostructural arrangement were studied. The Electron Beam Induced Current (EBIC) technique was used to monitor the hole recombination inside the quantum wells and to reveal the lateral inhomogeneities in the recombination velocity. The bright EBIC contrast associated with extended defects was revealed. This contrast was explained by a formation of channels with enhanced conductivity near the extended defects penetrating the active device region. 1 Introduction In spite of essential progress in the multiple quantum well (MQW) InGaN/GaN blue light emitting diodes (LED) technology, the reasons for rather high values of external quantum efficiency (QE) at low injection currents and its decrease at injection currents larger than 100 mA are not clear yet. The major part of investigations in this field dealt with studies of radiation recombination efficiency dependence on the In inhomogeneous distribution into InGaN layers leading to a quantum dot formation, on the layer thickness variation in MQW InGaN/GaN structures, on the polarization field and on dislocation density. However, the extended defect system in III-nitrides besides the threading dislocations includes also the typical for these materials mosaic structure, ordering of which could depend essentially on the defect system relaxation. For the well-ordered mosaic structures the defect relaxation occurs via the coherent concordance of mosaic structure domains with a formation of dilatation boundaries, while for the less-ordered mosaic structures the defect system relaxation occurs via the formation of numerous dislocated domain boundaries, the edge dislocation density in which exceeds essentially that of screw threading dislocations [1]. As shown in [2,3], the close correlation between mosaic structure ordering and the surface roughness allows the quantitative characterization of mosaic structure ordering by the multifractal analysis based on the atomic force microscopy data. However, in spite of essential ordering effect on the electrical and optical properties of hexagonal III-nitrides, the detail study of QE dependence in the III-nitride based LEDs on the nanostructural arrangement (NA) determined by the extended defect system relaxation was not carried out up to now.In the present work a comparative study of LEDs with the different NA has been carried out. The main purpose of this study is revealing a correlation between the NA and the electroluminescence efficiency and current-voltage (I -V) characteristics. The Electron Beam Induced Current (EBIC) technique
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