Systematic study on pulse parameters in fabricating porous silicon-layered structures by pulse electrochemical etching

Abstract

Pulse electrochemical etching was used to improve the quality of porous silicon (PS) layers. Although alternative PS layers of different porosities have been realized by this etching technique, there is no systematic study on the influence of different etching pulse parameters on PS during the etching process. We test various combinations of pulse parameters, including duty cycle and duration, in fabricating PS-layered structures. The optical thickness and actual thickness of the PS structures fabricated are investigated by means of reflectance spectroscopy and scanning electron microscopy. It is found that reducing the duty cycle and pulse duration of the pulse can promote the formation of PS layers with a large optical thickness and high refractive index. Meanwhile, the uniformity of PS is also improved. The duty cycle of 1:10–1:20 and pulse duration of 0.1–0.2 ms can result in the best uniformity and smoothness for the highly doped p-Si wafers. We believe that our work could set the foundation for further improvement of pulse electrochemical etching.