Quantified hole concentration in AlGaN nanowires for high-performance ultraviolet emittersElectronic supplementary information (ESI) available: Details of the SEM images of the AlGaN nanowires grown with different TMg values, RT PL and Raman spectra of the AlGaN nanowires grown with different TMg values, OCP measurements for all the samples, Mott-Schottky analysis of p-type Si, Mott-Schottky fitting data with the equations solved using cylindrical coordinates, FIB sample preparation, STEM images

• Main Authors: Zhao, Chao, Ebaid, Mohamed, Zhang, Huafan, Priante, Davide, Janjua, Bilal, Zhang, Daliang, Wei, Nini, Alhamoud, Abdullah A, Shakfa, Mohammad Khaled, Ng, Tien Khee, Ooi, Boon S
• Format: Journal Article
• Published: 30.08.2018
• DOI: 10.1039/c8nr02615g
• ISSN: 2040-3364

p-Type doping in wide bandgap and new classes of ultra-wide bandgap materials has long been a scientific and engineering problem. The challenges arise from the large activation energy of dopants and high densities of dislocations in materials. We report here, a significantly enhanced p-type conduction using high-quality AlGaN nanowires. For the first time, the hole concentration in Mg-doped AlGaN nanowires is quantified. The incorporation of Mg into AlGaN was verified by correlation with photoluminescence and Raman measurements. The open-circuit potential measurements further confirmed the p-type conductivity, while Mott-Schottky experiments measured a hole concentration of 1.3 × 10 19 cm −3 . These results from photoelectrochemical measurements allow us to design prototype ultraviolet (UV) light-emitting diodes (LEDs) incorporating the AlGaN quantum-disks-in-nanowire and an optimized p-type AlGaN contact layer for UV-transparency. The ∼335 nm LEDs exhibited a low turn-on voltage of 5 V with a series resistance of 32 Ω, due to the efficient p-type doping of the AlGaN nanowires. The bias-dependent Raman measurements further revealed the negligible self-heating of devices. This study provides an attractive solution to evaluate the electrical properties of AlGaN, which is applicable to other wide bandgap nanostructures. Our results are expected to open doors to new applications for wide and ultra-wide bandgap materials. Photoelectrochemical methods are implemented to quantify the hole concentration in AlGaN nanowires, calibrate doping conditions, and design ultraviolet light-emitting diodes.