Crack-free high quality 2-μm-thick Al0.5Ga0.5N grown on Si substrate with a superlattice transitional layer
The utilization of Si substrate 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 film grown on Si. In this letter, we reported the successful growth of a crack-free high-quality 2-μm-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 transitional 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 (10-12) reflection planes, respectively, revealing a low threading dislocation density of 3.3 × 109 cm-2. This work paves the way for the realization of cost-effective high-performance AlGaN-based DUV LEDs and photodetectors grown on Si platform.