Publication

Luminescence from Exciton-Free Carrier Collisions in GaSe

Jean-Louis Staehli
1991
Journal Articles

Abstract

Photoluminescence spectra of GaSe at moderately high densities of electron-hole pairs are reported for lattice temperatures between 2 to 200 K. We observed, at energies below the exciton recombination line, an additional narrow emission which has been attributed to exciton-free carrier scattering. Its narrowness at low temperatures is due to the selection rules for optical interband transitions in GaSe. Using numerical calculations based on second order perturbation theory, we fit quite well the experimental spectra. We find that the carriers which participate in the scattering process are electrons and holes at the center of the Brillouin zone (BZ), while the contribution of the electrons located at the M points of the BZ is negligible.

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https://infoscience.epfl.ch/entities/publication/37c7f644-8e3c-4957-bb9a-72b821018ba4

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Jean-Louis Staehli
1991
Journal Articles

Abstract

Official source

https://infoscience.epfl.ch/entities/publication/37c7f644-8e3c-4957-bb9a-72b821018ba4

About this result

Related concepts (32)

Photoluminescence

Photoluminescence (abbreviated as PL) is light emission from any form of matter after the absorption of photons (electromagnetic radiation). It is one of many forms of luminescence (light emission) and is initiated by photoexcitation (i.e. photons that excite electrons to a higher energy level in an atom), hence the prefix photo-. Following excitation, various relaxation processes typically occur in which other photons are re-radiated.

Emission spectrum

The emission spectrum of a chemical element or chemical compound is the spectrum of frequencies of electromagnetic radiation emitted due to an electron making a transition from a high energy state to a lower energy state. The photon energy of the emitted photon is equal to the energy difference between the two states. There are many possible electron transitions for each atom, and each transition has a specific energy difference. This collection of different transitions, leading to different radiated wavelengths, make up an emission spectrum.

Electron diffraction

Electron diffraction refers to changes in the direction of electron beams due to interactions with atoms. Close to the atoms the changes are described as Fresnel diffraction; far away they are called Fraunhofer diffraction. The resulting map of the directions of the electrons far from the sample (Fraunhofer diffraction) is called a diffraction pattern, see for instance Figure 1. These patterns are similar to x-ray and neutron diffraction patterns, and are used to study the atomic structure of gases, liquids, surfaces and bulk solids.

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Luminescence from Exciton-Free Carrier Collisions in GaSe

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