Optically pumped UV lasers grown on bulk AlN substrates
Optically pumped ultraviolet laser structures are demonstrated on low-defect-density bulk (0001) AlN substrates. The AlxGa1-xN/AlyGa1-yN hetero-structures were grown by metal-organic vapor phase epitaxy near atmospheric pressure. The hetero-structures included an AlN/AlGaN transition layer, n-AlGaN cladding layer, and AlGaN waveguide. The whole layer stack below the MQW region was designed for laser diodes emitting at 250 nm. The laser resonators with a length of about 1 mm were formed by cleaving the AlN crystal to obtain m-plane mirror facets. The facets were uncoated for the pump experiments. A KrF excimer laser with an emission wavelength of 248 nm was used as excitation source and focused to a stripe width of about 100 µm. Lasing was achieved with different test structures with emission wavelengths in range of 291 nm to 279 nm. Lasing threshold pump-power densities as low as 600 kW/cm2 were recorded and the laser emission was found to be TE polarized.
Wunderer, T.; Chua, C. L.; Yang, Z.; Northrup, J. E.; Kneissl, M. A.; Garrett, G.; Wraback, M.; Johnson, N. M. Optically pumped UV lasers grown on bulk AlN substrates. Ninth International Conference on Nitride Semiconductors; 2011 July 10-15; Glasgow, UK. (to appear in a special issue of physica status solidi c)