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Ambipolar Diffusion of Electron–Hole Pairs in β‐Rhombohedral Boron
Author(s) -
Werheit H.,
Kristen F.,
Franz R.
Publication year - 1992
Publication title -
physica status solidi (b)
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.51
H-Index - 109
eISSN - 1521-3951
pISSN - 0370-1972
DOI - 10.1002/pssb.2221720135
Subject(s) - ambipolar diffusion , electron , diffusion , excited state , relaxation (psychology) , chemistry , einstein relation , boron , atomic physics , analytical chemistry (journal) , materials science , thermodynamics , physics , psychology , social psychology , metric (unit) , operations management , organic chemistry , quantum mechanics , chromatography , economics
In β‐rhombohedral boron the electronic transport is essentially determined by deep electron traps of different bonding energies. The ambipolar diffusion of optically excited electron–hole pairs on diffusion paths of up to 5.37 mm length was investigated. The diffusion length at stationary conditions is 21 mm and the mean diffusion velocity is 5.8 × 10 −6 m s −1 . From these data a lifetime of 3620 s results. By Fick's second law the diffusion coefficient was determined to increase from about 5 × 10 −3 to 10 1 cm 2 s −1 with the diffusion velocity increasing from 10 −5 to 10 −1 m s −1 . The Einstein relation yields the corresponding mobilities, which increase accordingly from about 0.2 to about 50 cm 2 V −1 s −1 . These mobilities are mean values for electrons and holes. The relaxation of the excited state of the sample into the thermal equilibrium is determined by five relaxation times (6.6, 50, 514, 5650, 14700 s), which are immediately related to the thermal excitation of the electrons from the traps with the bond energies 0.18, 0.37, 0.58, 0.77, and 0.89 eV.