Improvement of surface roughness and reduction of threading dislocation density in AIN/AIGaN templates on sapphire by employing trimethylaluminum pulsed supply growth

摘要

We fabricated high-quality AIN/AIGaN templates, which are applicable to ultraviolet (UV) emitters on sapphire, by using a trimethylaluminum (TMAI) pulsed-supply growth method. We succeeded in achieving a dramatic improvement in the surface roughness of AIN/AIGaN layer by introducing a short-period pulsed supply of TMAI during the growth inter-vals of a 'standard' AIGaN growth regime. We speculate that the improvement in surface roughness is due to the realization of stable group III (+c) polarity by the growth of an Al-rich surface. In addition, we have found that this method is effec-tive for reducing threading dislocation densities (TDD). The TDD was reduced from 2.9× 10~9 to 1.1 × 10~9 cm~(-2) by introducing the TMAI pulsed supply growth. We fabricated a 350 nmband InAlGaN multi-quantum well (MQW) UV light-emitting diode (LED) on an AIN/AIGaN template formed by the TMAI pulsed supply method, and obtained an output power of 1.95 mW under room temperature (RT) CW operation. The output power of the LED was increased by a factor of 1.7 by introducing the TMAI pulsed supply method.