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The potential applications of germanium and its alloys in infrared silicon-based photonics have led to a renewed interest in their optical properties. In this letter, we report on the numerical determination of Auger coefficients at T=300K for relaxed and biaxially strained germanium. We use a Green's function based model that takes into account all relevant direct and phononassisted processes and perform calculations up to a strain level corresponding to the transition from indirect to direct energy gap. We have considered excess carrier concentrations ranging from 1016 cm-3 to 5×1019 cm-3. For use in device level simulations, we also provide fitting formulas for the calculated electron and hole Auger coefficients as functions of carrier density. [ABSTRACT FROM AUTHOR]

Recent experiments of electron emission spectroscopy (EES) on III-nitride light-emitting diodes (LEDs) have shown a correlation between droop onset and hot electron emission at the cesiated surface of the LED p-cap. The observed hot electrons have been interpreted as a direct signature of Auger recombination in the LED active region, as highly energetic Auger-excited electrons would be collected in long-lived satellite valleys of the conduction band so that they would not decay on their journey to the surface across the highly doped p-contact layer. We discuss this interpretation by using a full-band Monte Carlo model based on first-principles electronic structure and lattice dynamics calculations. The results of our analysis suggest that Auger-excited electrons cannot be unambiguously detected in the LED structures used in the EES experiments. Additional experimental and simulative work are necessary to unravel the complex physics of GaN cesiated surfaces. [ABSTRACT FROM AUTHOR]

A microscopic model, based on a full-Brillouin-zone description of the electronic structure, is used to investigate Auger transitions in InGaN/GaN quantum wells. The lack of momentum conservation along the confining direction enhances direct (i.e., phononless) Auger transitions, leading to Auger coefficients in the range of those predicted for phonon-dressed processes in bulk InGaN. The dependence of Auger coefficients on temperature and quantum well thickness is analyzed. The limitations of conventional multiband models, based on zone-center approximations of the band structure, are discussed. [ABSTRACT FROM AUTHOR]

Direct interband and intraband Auger recombination due to electron-electron-hole and hole-hole-electron transitions in bulk InGaN is investigated by first-order perturbation theory including Fermi statistics, realistic electronic structures obtained by nonlocal empirical pseudopotential calculations, and their corresponding wavevector-dependent dielectric functions. Our results confirm that the intraband Auger coefficient is negligible in alloy compositions relevant for solid-state lighting and indicate that the resonant enhancement associated with interband transitions for wavelengths ranging from blue to green cannot account for the efficiency droop experimentally observed in GaN-based light emitting diodes. [ABSTRACT FROM AUTHOR]

Indirect phonon-assisted Auger recombination mechanisms in bulk InGaN are investigated in the framework of perturbation theory, using first-principles phonon spectral density functions and electronic structures obtained by nonlocal empirical pseudopotential calculations. Nonpolar carrier-phonon interactions are treated within the rigid pseudoion framework, thus avoiding the introduction of empirical deformation potentials. The calculated indirect Auger coefficients exhibit a weak temperature dependence and dominate over direct processes for alloy compositions corresponding to the entire visible spectrum. The present results suggest that indirect Auger processes may be relevant in the operation of InGaN-based light-emitting diodes and lasers, at least in the yellow-green spectral region. [ABSTRACT FROM AUTHOR]