Effects of Low-Thermal-Budget Treatments on the Porous Si Material Properties

Our interest in porous silicon is due to its potential benefits in crystalline Si solar cells. Besides the use as an anti-reflection coating, the porous layer also acts as a light-diffusor. However major drawbacks are the significant light absorption within the porous layer and both insufficient as well as unstable surface passivating capabilities. The unstable nature of the porous Si is also reflected in the presence of suboxides after storage in ambient. In this work we focus on rapid-thermal-oxidation (RTO) and plasma-nitridation as low-thermal-budget chemical modification techniques in order to obtain a surface layer with a controlled and stable structure and composition. RTO of porous Si converts the material into SiO2 in conjunction with a drastically decreased porosity. Both a remote- and a direct-plasma nitridation of porous Si are able to incorporate nitrogen uniformly throughout the porous layer while preserving the porous character.