Credit: © (2006) JSAP

Aluminium nitride has a large bandgap of more than 6.0 eV and can withstand temperatures in excess of 3000 K. These properties are being exploited for the development of AlN-based ultraviolet light-emitting diodes and lasers. However, AlN films grown by metal–organic chemical vapour deposition and molecular beam epitaxy contain many crystalline defects because of the high growth temperatures required by these methods.

Now, Hiroshi Fujioka and colleagues1 from the University of Tokyo and Kanagawa Academy of Science and Technology have shown, for the first time, that pulsed laser deposition can be used to grow high-quality films of AlN on zinc oxide surfaces at room temperature. Atomically flat ZnO substrates were placed in a vacuum chamber and AlN films were deposited by ablation of a high-purity AlN target with a KrF excimer laser under a nitrogen plasma.

Nanoscale characterization using a variety of techniques showed that the AlN films crystallize by two-dimensional nucleation and exhibit a clear step–terrace structure. Moreover, the films were highly crystalline with a low density of defects and a well-defined abrupt interface between the AlN and ZnO. Layer-by-layer growth by pulsed laser deposition offers a new route towards the fabrication of high-performance group III nitride devices.