Improvement of far-field pattern in nitride laser diodes

We have clearly demonstrated a single spot in a far-field pattern of nitrid e-based laser diodes with a thick n-AlGaN layer/low-temperature-deposited b uffer layer/sapphire. This AlGaN-based structure has realized a crack-free 1-mu m-thick n-type Al0.06Ga0.94N cladding layer, leading to suppression of optical leakage from the waveguide region to the underlying layer and impr ovement of optical confinement. The threshold current of the laser diode is about 230 mA, which is comparable to or better than that of our laser diod es with the conventional GaN-based structure. (C) 1999 American Institute o f Physics. [S0003-6951(99)03045-4].