M. Munoz et al., Comment on 'modelling the optical constants of GaAs: excitonic effects at E-1, E-1+Delta(1) critical points', SEMIC SCI T, 16(4), 2001, pp. 281-282
Djurisic and Li [1] have recently presented a calculation of the optical co
nstants of GaAs in which they do not take into account excitonic effects at
either E-1, E-1 + Delta (1) or E-0, E-0 + Delta (0) critical points (CPs).
They employ band-to-band single-particle expressions with an energy-depend
ent pseudo-Gaussian broadening function. Their paper states that including
excitonic effects at the former CPs has 'dubious physical interpretation'.
It is also claimed that (a) 'excitonic effects are usually more pronounced
at E-0, E-0 + Delta (0) than at the E-1, E-1 + Delta (1) CPs', (b) 'at room
temperature the excitons are severely broadened and should not contribute
significantly to the dielectric function' and (c) 'excitonic effects at E-1
, E-1 + Delta (1) critical points do not represent a significant contributi
on to the dielectric function at room temperature for materials with low ex
citon binding energy'. These statements are completely incorrect, as is the
ir fitting scheme.