Effect of middle temperature intermediate layer on crystal quality of AlGaN grown on sapphire substrates by metalorganic chemical vapor deposition

We investigated the effect of a middle temperature intermediate layer (MTIL) of AlGaN and AlN/AlGaN super lattice structure (SLS) on the crystal quality of AlGaN epilayers grown by low-pressure metalorganic chemical vapor deposition (LP-MOCVD). MTIL-Al0.17Ga0.83N layers could enhance the lateral growth area at 950 °C, and the dislocations made dislocation loop. The full-width at half-maximum from (101¯2) X-ray rocking curve peak of HT-Al0.17Ga0.83N epilayers grown on MTIL decreased from 1220 to 525 arcsec. The dislocation density evaluated by atomic force microscopy density decreased from 1.0×1010 to 1.3×109 cm−2, respectively. These results reveal that MTIL technique is very useful to further improve the quality of AlGaN-based films, and to fabricate the high-efficiency ultra-violet light emitting diode (UV-LED).