Markus Thoenissen

Fabrication and properties of multilayer porous silicon filters

Porous silicon multilayer systems formed by different techniques were investigated. Type I layer systems are fabricated by changing the current density during the anodic etch process. Type II samples are formed with a constant current density but using a substrate with alternating doping levels. The superlattice structure is clearly visible in transmission electron microscope pictures. The quality of the interfaces depends on the formation technique. Porous silicon multilayer systems exhibit sharp peaks in the reflectance spectrum and can be used as filters. The line narrowing of the broad photoluminescence band of porous silicon by a Fabry- Perot filter structure is demonstrated.

Porous silicon - a new material studied by IR spectroscopy

We show how IR spectroscopy can be employed successfully in the analysis of porous silicon, e.g., to monitor important parameters as the hydrogen and oxygen concentration or the layer thickness nondestructively.