MBE-grown GaN lasers get lifetime boost
By Richard Stevenson in Montpellier, France
Valerie Bousquet of Sharp Laboratories of Europe (SLE) told the delegates at the International Conference on Blue Lasers and LEDs (ISBLLED) that her team has now extended the lifetime of its MBE-grown nitride lasers to 3 hours.
Although still much shorter than that of the MOCVD-grown nitride lasers that will feature in the first generation of HD-DVD and Blu-ray Disc players, three hours represents a significant improvement on the three minute figure reported last June (see related story).
The latest SLE lasers, which are grown on free-standing substrates produced by Sumitomo and Lumilog, deliver a continuous-wave output of 14 mW at a drive current of 450 mA and have a threshold voltage of 6.5 V.
This represents a 2 V improvement in the threshold voltage compared with previous attempts, and is due to a 15 ohm decrease in the resistance of the p-doped region. Bousquet and colleagues achieved that by switching from a supperlattice structure to a bulk region.
However, she believes that the threshold voltage will need to drop by a further 1.5 V, and be accompanied by a similar fall in the threshold current density, for further improvement to the laser lifetime.
