To tackle this issue, selective area growth (SAG) of nitride NCs by plasma assisted molecular beam epitaxy (PAMBE) has been developed, where the substrate is covered by a nanohole Ti mask. The figure above shows a typical SEM image of SAG InGaN/GaN NCs on a silicon substrate, as well as PL spectra of InGaN/GaN samples that can be fabricated to cover the energy range from UV to IR by varying the In content.

The research team (ISOM at Universidad Politecnica of Madrid) has been working on the growth and characterization of nitride nanocolumns since 1997, with special focus on ordered InGaN and GaN nanocolumns during the last 5 years.

Very wide spectral range

Recently, they obtained for the first time ordered In(Ga)N/GaN nanocolumns on cheap, easy to process silicon substrates with emission wavelengths ranging from the ultraviolet to the infrared. In addition, morphology optimized NCs emitting in the green spectral range with an estimated internal quantum efficiency (IQE) of 36% have been achieved on silicon by ISOM. These results pave the way to develop LEDs and detectors based on ordered InGaN structures on Si substrates over a very wide spectral range.

Other research lines currently followed by the team at ISOM are: i) SAG of InGaN and GaN NCs on semi-polar and non-polar substrates; ii) SAG of InGaN/GaN dot-in-a-wire structures; iii) fabrication of high-quality, strain-free GaN and InGaN templates (pseudo-substrates) by NCs coalescence (both non-polar and semi-polar); and iv) SAG of core-shell InGaN/GaN structures by PAMBE.

The researchers published their results in the journal Nanotechnology.