I. Introduction
The preparation of porous semiconductors has displayed a great deal of research interest in recent years, primarily due to their unique optical properties compared to the bulk material as well as the potential applications in optoelectronics, chemical and biochemical sensing [1]–[4]. The high surface area, shift of band gap, luminescence intensity enhancement, as well as efficient photoresponse when porosity is formed can be tailored to fabricate new sensing devices [5]–[7]. Since the discovery of visible luminescence from porous Silicon in 1990 [3], this leads to the development of other porous semiconductors, for instance, the conventional 111-V compounds such as GaAs, GaP and InP, and the wide bandgap materials such as GaN and SiC [2,9–17].