Monte Carlo Modelisation of Photoexcited Carriers Relaxation including Auger Effect in Narrow Band Gap InGaAs
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Monte Carlo Modelisation of Photoexcited Carriers Relaxation including Auger Effect in Narrow Band Gap InGaAs. Eric Tea1 and Frederic Aniel1 1 Institut d’Electronique Fondamentale, UMR 8622 CNRS, Université Paris Sud 91405 Orsay Cedex, France. ABSTRACT The Auger effect is one of the fastest recombination mechanism in narrow band gap semiconductors at high carrier concentration. This regime is of great interest for high efficiency hot carrier solar cells application and is also involed in many optical devices. Therefore, the knowledge of this limitting process is required for the determination of carrier lifetime useful to accurate solar cell efficiency calculations. For the first time, we present a carrier lifetime study versus carrier concentration in InGaAs based on a Monte Carlo model where the Auger effect is included as a relaxation mecanism. INTRODUCTION The InGaAs ternary alloy semiconductor has several assets: the composition In0.53Ga0.47As is lattice matched on InP, the electrons’ mobility is high (~11000 cm2/Vs) and its band gap is particularly well suited for telecommunication applications. InGaAs is already used in multijunction solar cells and is also a candidate for high efficiency hot carrier solar cells due to this materials controllable band gap and lattice parameter. But when the InGaAs layer contains a high carrier density, Auger recombinations limits its performances. In the present paper, we calculate electrons’ lifetimes in the case of a bulk In0.53Ga0.47As using the Monte Carlo (MC) technique. We will first describe the content of the MC model and then present electrons’ lifetimes, in p-type In0.53Ga0.47As, calculation results. THEORY The Monte Carlo (MC) technique is used to solve the Boltzmann Transport Equation to determine the carriers’ distribution functions. In our model, the first conduction band is represented by valleys (Γ, L and X) characterized by the electrons’ effective masses and non parabolicity coefficients. The Γ valley is isotropic whereas the L and X valleys’ iso-energy surfaces are modeled as ellipsoids. The highly anisotropic dispersions of the heavy holes (HH) and light holes (LH) valence bands are fully taken into account . They are calculated with a non local Empirical Pseudopotential Method (EPM) including spin orbit [1]. The pseudopotentials are obtained by interpolation from the GaAs and InAs binary compounds taking into account the disorder to reproduce the bowing parameters when the composition changes. The split-off band (SO) is much less anisotropic than the HH and LH bands. Therefore, we neglect its anisotropy and model it by a non parabolic band. The following scattering processes are accounted for:
carrier-polar optical phonon (POP) , carrier-non polar optical phonon, carrier-acoustic phonon, piezoelectric scattering, alloy scattering, carrier-ionized impurities and all binary carrier-carrier collisions : electron-electron, hole-hole, electron-hole, hole-electron. The carrier-POP interaction is accounted for by the Frohlich coupling constant. A
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