Intrinsic recombination in dependence on doping concentration and excitation level application to lead chalcogenides

Abstract

On the base of anisotropic and parabolic band structure recombination rates are calculated for the mixed crystals Pb0.78Sno.22Te and PbSo.lSeo.9 in dependence on non-equilibrium carrier concentration 6n up to 1020 cm-9 in a wide range of temperatures and doping levels. Degeneracy causes different changes of lifetimes or recombination rates for material with different activation energies of the recombination process. Both, weakening or strengthening of the known n2pp-law of the Auger transition rate can occur at beginning degeneracy. At 6n > 10'9 ~m -~ always sublinear behaviour should be observed. For radiative recombination a weakening of the np-law is obtained generally; in the limit 6n > 10'9 cm-a the rate behaves like (6n)4/3.Unter Zugrundelegung anisotroper parabolischer Bandstruktur werden fur die Mischkristalle Pbo,7~Sno,22Te und PbSo,lSeo,o Rekombinationsraten in Abhiingigkeit von der Nichtgleichgewichtskonzentration 6n (bis zu 6n = 10ao fiir einen weiten Temperatur-und Dotierungsbereich berechnet. Entartung verursacht unterschiedliche Veranderungen der Lebensdauer bzw. der Rekombinationsrate fiir Substanzen mit unterschiedlicher Aktivierungsenergie des Rekombinationsprozesses. Sowohl eine Schwichnng als auch eine Verstarkung der bekannten n2p-Abhiingigkeit, der Auger-Rate kann infolge beginnender Entartung auftreten. Bei 6n > l O l g cm-s sollte aber immer sublineares Verhalten zu beobachten sein. Entartung fiihrt bei strahlender Rekombination in jedem Falle zu einer Schwachung des np-Gesetzes; im Grenziibergang (etwn ab 6n > > 10'9 cnir8) verhiilt sich die Rate hier wie (6n)4/3.

Auger recombination dynamics of lead salts under picosecond free-electron-laser excitation

“…A particular feature of this system-i.e., their near ''mirror'' conduction and valence bands-has been cited as potentially leading to much smaller Auger scattering rates than found in III-V material systems. However, theory predicts that there may nevertheless still remain a substantial contribution to this unwanted recombination process through intervalley scattering, [1][2][3][4] although later theories, [2][3][4] including more realistic band-structure pictures, suggest that this should not be as serious as originally predicted. 1 Understanding accurately how the recombination processes change with carrier density is important for emission devices which operate far from equilibrium, and in particular in the continuing quest for the development of compact MIR room-temperature lasers.…”

“…The sophistication of a three-beam pump-probe experimental technique described below has enabled an analysis of the decay at times longer than 100 ps in terms of the nonparabolic anisotropic band structure of the lead salts, to give the Auger coefficient C qualitatively over a wide temperature range 30-300 K. The results are in good agreement with theory for nonparabolic, anisotropic bands 11,12 and nondegenerate statistics, 2 and confirm that the original parabolic band calculations 1 underestimated the measured lifetime by more than an order of magnitude. [2][3][4]6 Finally the Auger results for the lead salts are compared with earlier measurements taken at FELIX ͑Ref. 13͒ for Hg 1Ϫx Cd x Te of a composition such that the band gap for the two semiconductors is the same at Tϭ100 K. 13 It is found that C for PbSe is between one and two orders of magnitude lower than for Hg 1Ϫx Cd x Te over the whole temperature range for comparable values of the band gap.…”

Auger Recombination in Low-Dimensional PbSnTe Structures

“…A characteristic two-valley process [3] dominates the Auger recombination in lead chalcogenides with strong anisotropic band structure (e.g. PbTe, PbSnTe).…”

“…For bulk lead chalcogenides it is well-known [3] that increasing band stucture anisotropy and decreasing gap energy (following e.g. the series PbSSe, PbSnSe, PbSnTe) give rise to an increasing Auger recombination rate.…”