Characteristics of epitaxial lateral overgrowth AlN templates on (111)Si substrates for AlGaN deep‐UV LEDs fabricated on different direction stripe patterns

We investigated the characteristics of epitaxial lateral overgrowth (ELO) AlN templates fabricated on Si substrates which are applicable to AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs). ELO-AlN layers were grown on stripe-patterned thin AlN seed-layer directly deposited on (111)Si substrates by using an ‘NH3 pulsed-flow multi-layer (ML) growth’ technique. A 4 µm-thick ELO-AlN layer with stripe pattern along direction of AlN can be coalesced successfully. We achieved marked reduction of crack and threading dislocation density (TDD) in the ELO AlN layers. In fact, the (10-12) full width at half maximum (FWHM) of the X-ray diffraction ω-scan rocking curves (XRCs) of ELO-AlN template on Si substrate was reduced to be 980 arcsec. These results show that the combination of NH3 pulsed-flow ML growth and ELO method is effective to fabricate high-quality AlN templates on Si substrates. Moreover we fabricated 256-278 nm AlGaN quantum well (QW) DUV LEDs on the low TDD ELO-AlN templates on Si, and achieved single-peak operations under room temperature (RT) cw current injection. The low cost AlGaN based DUV LEDs on Si substrates is expected to be integrated with Si based electric devices on the same chips. (© 2012 WILEY-VCH Verlag GmbH & Co. KGaA, Weinheim)