Superlattice

The term superlattice (English superlattice ) denotes a solid man-made, consisting of a series of thin layers that are periodically repeated. Most are two alternating layers, which differ in the size of the band gap and the film thickness. The electrons ( or holes) are then in a periodically modulated conduction band ( valence band ). The dispersion in the direction of the superlattice axis results in principle, exactly as in the crystal. Since the period is larger than the lattice constant, the Brillouin zone is always smaller than that of the crystal band structure. Because you can, in contrast to the naturally occurring solids, with the parameters of the superlattice determine the energy spectrum of the charge carriers, it is called an artificial band structure and in particular of mini bands.

The preparation of heterostructures can be done by molecular beam epitaxy, CVD or MOVPE.

The periodic disturbances of the grid structure have an effect on the charge carrier of the original material and modify its properties. For example, the mobility of the charge carriers are significantly increased ( application in high-frequency technology, microwave diodes) or the optical properties can be set ( semiconductor laser).

The quality of the superlattice the accuracy of the layer sequences is critical. The layer thicknesses are partly in the order of a few atomic layers. Where can be detected through changes in properties of the electron deviations of one atomic layer.

Quality analyzes are possible with different measurement methods.

A more macroscopic view of the overall properties of the crystal provide Luminescence. An atomic view provides the tunneling microscopy. Investigations by magnetic resonance methods are intervening in the measurement accuracy.

• Solid State Physics