(Invited) Fully Porous GaN p-n Junctions Fabricated by Chemical Vapor Deposition: A Green Technology towards More Efficient LEDs

Tuesday, 26 May 2015: 12:00
Conference Room 4C (Hilton Chicago)
J. J. Carvajal, J. Mena, O. Bilousov (FiCMA-FiCNA, University Rovira i Virgili), O. Martínez, J. Jiménez (GdS-Optronlab, Universtiy of Valladolid), V. Z. Zubialevich (Tyndall National Institute), P. J. Parbrook (Tyndall National Insitute, University College Cork), H. Geaney (University College Cork, Tyndall National Institute), C. O'Dwyer (Tyndall National Institute, University College Cork), F. Díaz, and M. Aguiló (FiCMA-FiCNA, University Rovira i Virgili)
GaN is an important wide band-gap semiconductor in electronics and optoelectronics. In its porous form is particularly interesting for developing optoelectronic devices with improved efficiency, such as LEDs with enhanced efficiency and sensors with enhanced sensitivity.

Through chemical vapour deposition (CVD) [1], we have shown that it was possible to produce nanoporous GaN without any secondary etching or chemical post-growth treatment in order to generate the porosity, present only on the (0001) face of the material, providing a green approach for the production of porous GaN. These nanoporous GaN particles can be deposited on different substrates, including boron nitride, silicon, sapphire and SiC, obtaining porous particles with a low density of defects, as revealed by the emission arising only from the band-edge of the particles obtained in the cathodoluminescence studies [2]. By using this methodology of growth, we demonstrated the fabrication of low resistivity ohmic Pt and Au metallic contacts on porous n-type GaN by the formation of intermetallic seed layers through the vapour-solid-solid (VSS) mechanism [3]. 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 [4].

Through the careful selection of the substrate it is 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 2 step CVD process, and show their behaviour as diodes with effective uniform conduction [6]. 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] Carvajal et al., Microsc. Microanal. 18 (2012) 905

[3] Bilousov et al., ACS Appl. Mater. Interfaces 4 (2012) 6927

[4] Bilousov et al., Appl. Phys. Lett. 103 (2013) 112103

[5] Bilousov et al., CrystEngComm  16 (2014) 10255

[6] Bilousov et al., ACS Appl. Mater. Interfaces 6 (2014) 17954