Fast growth of crack-free thick AlN film on sputtered AlN/sapphire by introducing high-density nano-voids

Abstract Recently, there have been increasing demands for high-quality AlN/sapphire templates due to their applications in deep ultraviolet light-emitting diodes (DUV LEDs). To acquire a low threading dislocation density (TDD), AlN films are usually thickened to promote dislocation interaction. However, micro cracks are easily generated when their thicknesses exceed 2–3 μ m, severely deteriorating device performances. In this study, we successfully fabricated a 5.6 μ m-thick crack-free AlN film by employing a medium-temperature (MT) interlayer. It is revealed that high-density (1.7 × 10 10 cm −2 ) nano-voids were self-organized above the MT interlayer, which effectively destroyed the coherence between the MT interlayer and the subsequent epilayer by reducing contact area. As a result, tensile stress in the AlN film during growth was significantly decreased to 0.18 GPa, demonstrating a 64% reduction compared with its counterpart without nano-voids. In addition, the thick AlN film with embeded nano-voids allowed dislocations to climb long distances for mutual annihilation, so the TDD of the AlN film was significantly decreased to an extremely low value of 4.7 × 10 7 cm −2 . This technique paves the way for achieving high-performance DUV LEDs and other optoelectronic/electronic devices.