Understanding the p-Type GaN Nanocrystals on InGaN Nanowire Heterostructures

The efficiency of semiconductor light-emitting diodes (LEDs) has been largely limited by the extremely inefficient p-type conduction on InGaN heterostructures. Here we report highly efficient p-type GaN nanocrystals fabricated by p–i–n nanowire heterostructures using selective area epitaxial growth (SAG). With the different Mg-doping growth conditions in the p-GaN nanostructure, different structure formations and various Mg incorporations were confirmed by detailed scanning electron microscopy and cathodoluminescence analysis. The growth mechanism of p-GaN nanocrystal formation on nanowire structures was also suggested by CL mapping measurements. Single nanowire LEDs exhibited different current–voltage behaviors from various p-GaN nanocrystal formations. The resulting p-contacted InGaN/GaN nanowire LEDs showed a low turn-on voltage (∼2.3 V), reduced resistance, and enhanced electroluminescence intensity at 532 nm wavelength, which is very important for realizing high-efficiency InGaN LEDs operating in the green and red wavelength ranges. This demonstration provides important insight into the fundamental formation characteristics of p-GaN nanocrystals on the nanowire heterostructure and also offers a viable path for realizing multifunctional nanoscale photonic and electronic devices.