Cavity structures

Long spin lifetimes as well as a high degree of conversion from light into charge carriers are essential for long distance spin transport via, e.g., surface acoustic waves.

Long spin lifetimes can be achieved particularly in quantum well structures with (110) orientation and semiconductor cavity structures are capable of converting light into charge carriers very effectively. 

However, the limits of elastic behavior of GaAs/AlAs or GaAs/(Al,Ga)As based layer stacks for cavities with Bragg reflectors on GaAs are narrower for the (110) orientation compared to the (001) orientation. Exceeding this limit results into the generation of structural imperfection.

By replacing consequently the thick AlAs or (Al,Ga)As components of the Bragg reflectors (lambda quater layers) by short-period supperlattices with an equivalent effective refractive index, the total structure is stabilized against lattice relaxation and defect-free cavity structures are successfully fabricated.

Scanning electron micrograph displaying a cross-sectional view of an asymmetric cavity with a 10.5 pair bottom DBR, a cavity (broader gray stripe), and a 5 pair top DBR grown on GaAs(110). All constituent layers of the DBRs are made of AlAs/GaAs  short-period superlattices.