Sapphire Interlayer Aids GaN-on-Si LED Output
Ian Ferguson and co-workers at Georgia Institute of Technology have produced crackfree GaN-on-silicon LEDs that feature an Al2O3 interlayer and produce similar internal quantum efficiencies to controls grown on sapphire.
Silicon substrates are a desirable platform for LED production due to their low cost. However, successful growth of LEDs on silicon requires overcoming issues related to the thermal and lattice mismatch between the two materials.
Ferguson’s team has addressed this by adding a 5–20 nm thick Al2O3 interlayer by atomic layer deposition, before growing nitride epilayers in an Emcore D-125 MOCVD system.
The silicon-based devices emit at a longer wavelength than their sapphire counterparts, due to tensile strain and higher indium composition in the active layer. Two emission peaks are produced by this LED and the researchers believe that this may be caused by non-uniformity in the composition of the InGaN in the quantum wells.
The researchers fabricated their LEDs on 2 inch silicon substrates that were cut into halves or quarters. “The size limitation stems from our oxide deposition system, which until recently could only accommodate these smaller wafer sizes," said lead author William Fenwick.
Reducing LED manufacturing costs will require the growth of devices on far larger silicon substrates, where issues such as wafer bow and thin-film uniformity come into play. “However, our initial attempts to scale the process to larger substrates have shown promise," said Fenwick, “and we are hopeful that we can demonstrate a process on larger silicon substrates in the near future."
He believes that the particular architecture of the team’s LEDs will allow novel approaches to device processing. “The use of the oxide layer will allow for wet etch removal of the substrate, opening the door to new approaches to light extraction and thermal management."
AngelTech Live III: Join us on 12 April 2021!
AngelTech Live III will be broadcast on 12 April 2021, 10am BST, rebroadcast on 14 April (10am CTT) and 16 April (10am PST)
and will feature online
versions of the market-leading physical events: CS International
and PIC International
PLUS a brand new Silicon Semiconductor International
Thanks to the great diversity of the semiconductor industry, we are always chasing new markets and developing a range of exciting technologies.
2021 is no different. Over the last few months interest in deep-UV LEDs has rocketed, due to its capability to disinfect and sanitise areas and combat Covid-19. We shall consider a roadmap for this device, along with technologies for boosting its output.
We shall also look at microLEDs, a display with many wonderful attributes, identifying processes for handling the mass transfer of tiny emitters that hold the key to commercialisation of this technology.
We shall also discuss electrification of transportation, underpinned by wide bandgap power electronics and supported by blue lasers that are ideal for processing copper.
Additional areas we will cover include the development of GaN ICs, to improve the reach of power electronics; the great strides that have been made with gallium oxide; and a look at new materials, such as cubic GaN and AlScN.
Having attracted 1500 delegates over the last 2 online summits, the 3rd event promises to be even bigger and better – with 3 interactive sessions over 1 day and will once again prove to be a key event across the semiconductor and photonic integrated circuits calendar.
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