Through chemical vapour deposition (CVD) [1], we have shown that it is possible to produce nanoporous GaN without any etching or chemical post-growth treatment, with the porosity being present only on the (0001) face of the material. Low resistivity ohmic Pt and Au metallic contacts were demonstrated on porous n-type GaN by the formation of intermetallic seed layers through the vapour-solid-solid (VSS) mechanism [2]. Also, we have been able to develop p-type porous GaN by doping with Mg, with a charge carrier concentration of the order of 1018 cm-3 [3]. By tuning the concentration of Mg, introduced as Mg2N3 in the CVD system, it has been possible to form a polycrystalline high-k oxide between an ohmic metallic alloy interlayer contact and the porous GaN, while maintaining a clean interface, that allowed to fabricate a MOS-type diode on silicon in a single growth regime [4].
Through the careful selection of the substrate it has also been possible to produce porous GaN epitaxial layers [5] that allow for the fabrication of high quality partially and fully porous GaN rectifying p-n junctions, through a two step CVD process, and show their behaviour as diodes with effective uniform conduction under a green technology [6]. Here, we will also present the recent results we obtained in the light emission of these structures. Thus, these porous junctions have potential applications in high brightness unencapsulated LEDs with enhanced light emitting properties and high surface area sensors with improved sensitivity.
[1] Carvajal & Rojo, Crystal Growth Des., 9 (2009) 320
[2] Bilousov et al., ACS Appl. Mater. Interfaces 4 (2012) 6927
[3] Bilousov et al., Appl. Phys. Lett. 103 (2013) 112103
[4] Bilousov et al., Chem. Mater. 26 (2014) 1243
[5] Bilousov et al., CrystEngComm 16 (2014) 10255; Bilousov et al., ACS Appl. Mater. Interfaces 6 (2014) 17954
[6] Carvajal et al., ECS Transactions 66 (2015) 163