Abstract
Photogeneration of excess charge carriers in semiconductors produces electronic strain. Under transient conditions, electron-hole pairs may be separated across a potential barrier. Using time-resolved X-ray diffraction measurements across an intrinsic AlGaAs/n-doped GaAs interface, we find that the electronic strain is only produced by holes, and that electrons are not directly observable by strain measurements. The presence of photoinduced charge carriers in the n-doped GaAs is indirectly confirmed by delayed heat generation via recombination.
Highlights
Deformation potential theory was originally developed by Bardeen and Shockley [1] to describe the interactions between thermal electrons and acoustic vibrational modes in non-polar crystals
In some materials the electronic strains can be quite large; for instance [4] found the electronic strain in Silicon irradiated with 514.5 nm laser light was 2.6 times larger than the strain generated by thermal expansion under the same conditions
We find surprisingly that the electronic strain does not transport across the interface along with the electrons, indicating that holes are primarily responsible for electronic strain
Summary
Deformation potential theory was originally developed by Bardeen and Shockley [1] to describe the interactions between thermal electrons and acoustic vibrational modes in non-polar crystals. The theory predicts a dependence of the energy band gap upon dilation; changes in energy band structure result in changes in carrier concentration. This effect of the deformation potential has been exploited in several applications such as strain transducers [2]. It was soon realized that the deformation potential effect can be inverted to explain the generation of electronic strain Sel by charge carriers in cubic semiconductors [3], 1 dEg Sel = ∆n (1). Studies of photogenerated electronic strain have been undertaken using modulated laser beams to produce photo-acoustic waves [4] as well as by direct imaging of opticaly-excited semiconductors in a scanning probe microscope [5]. In some materials the electronic strains can be quite large; for instance [4] found the electronic strain in Silicon irradiated with 514.5 nm laser light was 2.6 times larger than the strain generated by thermal expansion under the same conditions
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