Monolithic LEDs tunable from 460 to 650nm

January 26, 2017 // By Julien Happich
Optoelectronics startup Ostendo Technologies has on its roadmap portable light-field displays able to project full 3D holograms out of tiny chips built using standard semiconductor processing equipment. Of course, in order to deliver the right level of resolution, the individual voxels and micro-optics of such a projector chip ought to be drastically shrunk so the whole chip may easily fit within today's slim smartphones.

One step in that direction comes in the shape of monolithically integrated full colour LED arrays, where each individual LED can be driven to output just any colour including a full white mix. This is no small feat in the world of LED design was achieved by researchers at Ostendo Technologies and was the topic of a recent publication in AIP Advances under the title "Growth of monolithic full-color GaN-based LED with intermediate carrier blocking layers".

In this paper, lead author Dr. Hussein S. El-Ghoroury who also happens to be Ostendo Technologies' Founder and CEO shares a novel tricolour InGaN-based LED design obtained through a common metal-organic chemical deposition (MOCVD) process.

A simplified schematic cross-sectional view of a monolithic tricolour multi-layer InGaN-based LED structure.

His team relied on specially designed intermediate carrier blocking layers (ICBLs) to control the carrier injection distribution across the active regions of multiple quantum wells stacked one upon another, effectively guiding the majority of carriers into the designed quantum wells so they would recombine and generate light at the QW's specific wavelengths depending on the current-densities running throughout the device.

The monolithic InGaN-based LED they designed is able to achieve three primary colours of light from one device at selected current densities, starting at 650nm and then decreasing to 460nm or lower as the injection current increases.