Fabrication and characterization of GaN-based laser diode grown on thick n-AlGaN contact layer

n-AlGaN has been introduced as a new n-type contact layer for a GaN-bascd l aser diode (LD) prepared on sapphire substrate. Cracks, generated by the la ttice mismatch between n-AlGaN cladding layer and n-GaN contact layer in a typical LD, have been extremely reduced. Under the pulse lasing conditions at room temperature, the threshold current was about 239 mA. Lasing wavelen gth was 405 nm. Moreover, there is also great improvement in the optical:co nfinement for this new LD structure. Both near-field and far-field patterns manifested a clear single spot.