UK-based Sharp Laboratories of Europe has made the first blue-violet laser diodes to
be grown using MBE.
Scientists at Sharp Laboratories of Europe (SLE) have produced the world’s first
blue-violet laser diodes fabricated using MBE.
Jonathan Heffernan and colleagues at the UK-based subsidiary of the Japanese
electronics giant reported their work in the latest issue of the journal Electronics
Grown on a sapphire substrate, the ridge waveguide InGaN multiple quantum well
lasers operate at room temperature with an output wavelength of 400 nm.
To date, only low-power blue LEDs have been fabricated using MBE. The blue LEDs and
lasers developed by Shuji Nakamura and colleagues at Nichia Chemical Industries in
Japan in the mid-1990s were all fabricated using MOVPE and this technique has
dominated since then.
SLE says that is has a patented MBE system that has been specifically designed for
growing GaN devices.
One key advantage of the MBE method is its much lower consumption of source
materials for device growth, in particular the amount of ammonia required as the
source of nitrogen.
According to Heffernan and colleagues, another significant difference is that the
MBE-grown devices require no post-growth thermal annealing to activate the p-type
dopant, a process that is required for devices fabricated using MOVPE.
The SLE team is still some way short of producing commercial-grade devices, however.
At the laser threshold current of 1.5 A, the operating voltage was 33 V. The
threshold current density is approximately 30 kAcm-2.
The lasers currently operate in pulsed mode with a pulsewidth of 200 ns. For
commercial applications, a continuous-wave device would be required.