Effect of porosity on the characteristics of GaN grown on sapphire

The preparation of porous semiconductors has attracted a great deal of research interest in recent years, primarily due to the potential for intentional engineering of properties not readily obtained in the corresponding crystalline precursors as well as the potential applications in optoelectronics, chemical and biochemical sensing [1–4]. When porosity is formed, these materials exhibit various special optical features, for instance, the shift of bandgap [5], luminescence intensity enhancement [6], as well as photoresponse improvement [7]. To date, porous silicon (Si) receives enormous attention and has been investigated most intensively; however the instability of physical properties has prevented it from large scale applications [8]. Thus, this leads to the development of other porous semiconductors, for instance, the wide bandgap materials such as GaN [2].