Crack-free high quality 2 mu m-thick Al0.5Ga0.5N grown on a Si substrate with a superlattice transition layer

The utilization of Si substrates to fabricate AlGaN-based deep ultraviolet (DUV) light-emitting diodes (LEDs) is deemed as an effective way to improve light extraction efficiency with the thin-film flip-chip architecture, which calls for crack-free high-quality high Al-content AlGaN films grown on Si. In this study, we reported the successful growth of a crack-free high-quality 2 mu m-thick Al0.5Ga0.5N film grown on planar Si by metal-organic chemical vapor deposition. A smooth surface with a root-mean-square roughness of 1.5 nm was obtained by employing a superlattice transition layer. Double crystal X-ray rocking curves yielded full widths at half maximum of 499 and 648 arcsec for the Al0.5Ga0.5N (0002) and (10 (1) over bar2) reflection planes, respectively, revealing a low threading dislocation density of 3.8 x 10(9) cm(-2). This work paves the way for the realization of cost-effective high-performance AlGaN-based DUV LEDs and photodetectors grown on a Si platform.