Chapter 9
Optical Properties
Do not Bodies and Light act mutually upon one another.
Sir I. Newton, 1704 [826]
Abstract After introduction of the complex dielectric function, reflection, diffraction are briefly discussed. The focus lies on absorption mechanisms; several transition types (direct and indirect band-band
transitions, impurity-related transitions, lattice absorption) are discussed including the effects of excitons, polaritons and high carrier density. Also the various effects of the presence of free carriers are
given.
9.1 Spectral Regions and Overview
The interaction of semiconductors with light is of decisive importance for photonic and optoelectronic
devices as well as for the characterization of semiconductor properties. When light hits a semiconductor,
reflection, transmission and absorption are considered, as for any dielectric material. The response of
the semiconductor largely depends on the photon energy (or wavelength) of the light and various
processes contribute to the dielectric function.
An overview of the electromagnetic spectrum in the optical range is given in Table 9.1. The energy
and wavelength of a photon are related by
1 E = hν = hc/λ, i.e.
E [eV] =
1240
λ [nm]
.
(9.1)
In the infrared regime, energy is often measured in wave numbers (cm
−1 ) for which the conversion
1 meV= 8.056 cm
−1 holds.
1 The more exact numerical value in (9.1) is 1239.84.
© Springer Nature Switzerland AG 2021
M. Grundmann, The Physics of Semiconductors, Graduate Texts in Physics,
https://doi.org/10.1007/978-3-030-51569-0_9
257
Optical Properties
Do not Bodies and Light act mutually upon one another.
Sir I. Newton, 1704 [826]
Abstract After introduction of the complex dielectric function, reflection, diffraction are briefly discussed. The focus lies on absorption mechanisms; several transition types (direct and indirect band-band
transitions, impurity-related transitions, lattice absorption) are discussed including the effects of excitons, polaritons and high carrier density. Also the various effects of the presence of free carriers are
given.
9.1 Spectral Regions and Overview
The interaction of semiconductors with light is of decisive importance for photonic and optoelectronic
devices as well as for the characterization of semiconductor properties. When light hits a semiconductor,
reflection, transmission and absorption are considered, as for any dielectric material. The response of
the semiconductor largely depends on the photon energy (or wavelength) of the light and various
processes contribute to the dielectric function.
An overview of the electromagnetic spectrum in the optical range is given in Table 9.1. The energy
and wavelength of a photon are related by
1 E = hν = hc/λ, i.e.
E [eV] =
1240
λ [nm]
.
(9.1)
In the infrared regime, energy is often measured in wave numbers (cm
−1 ) for which the conversion
1 meV= 8.056 cm
−1 holds.
1 The more exact numerical value in (9.1) is 1239.84.
© Springer Nature Switzerland AG 2021
M. Grundmann, The Physics of Semiconductors, Graduate Texts in Physics,
https://doi.org/10.1007/978-3-030-51569-0_9
257