Abstract
The growth of AlN thin films on (0 0 0 1) sapphire by metal-organic chemical vapor-phase epitaxy has been investigated to serve as the template layer of deep-ultraviolet light-emitting diodes. Delayed coalescence of AlN films resulted in a low threading dislocation density of 5×10 9 cm −2 for a 2.1 μm thick film compared to partially coalesced 1.05 μm films exhibiting a threading dislocation density of 1.1×10 10 cm −2. The reduction in dislocation density results from a decrease in the number of edge character threading dislocations, while the screw character density remains virtually unchanged, as determined by X-ray rocking curve measurements of the AlN off-axis ( 2 0 2 ¯ 1 ) and on-axis (0 0 0 2) reflections, respectively. Cross-sectional transmission electron microscopy indicates the presence of a number of inversion domains in the AlN films. Electrically injected, 317 nm Al x Ga 1− x N LEDs were successfully fabricated, with a maximum output power of 17.7 μW tested on wafer at 160 mA DC. Using a 248 nm KrF excimer laser, a 2.8 μm thick AlN film was debonded from the sapphire substrate using a laser pulse power of 1 J/cm 2. However, substrate debonding of an Al x Ga 1− x N/AlN LED layer could not be achieved.
Published Version
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