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Palo Alto Research Center (PARC) and Crystal IS demonstrate the first UV-LED on AlN substrates

1 April 2002

Palo Alto Research Center (PARC) and Crystal IS announce the first demonstration of an optoelectronic device grown on a single crystal substrate of AlN. The device, an ultra violet light emitting diode (UV LED), was recently demonstrated at PARC utilizing substrates produced by Crystal IS. Single crystal AlN substrates present an excellent template for the growth of AlGaN alloys, because of their chemical compatibility, well-matched crystal structure and thermal expansion coefficients. An important application of solid-state UV optical sources is anticipated to be compact and highly sensitive bioagent detection systems for airborne pathogens like Anthrax spores. Other potential applications of UV LEDs include solid-state white lighting, sterilization and disinfectant devices, and compact analytical devices for the biotechnology and pharmaceutical markets.

 

UV-LED emission spectra measured at different drive currents. The UV-LED was grown on a single crystal (0-112) AlN substrate with a Si-doped graded AlGaN transition layer.

These are atomic force microscopy images of an (10-11) AlN substrate before and after AlN homoepitaxy. The initial RMS roughness in a 1-mm square prior to epitaxy was 0.83 nm and this value decreased to 0.38 nm after AlN epitaxy.

The LED structure consisted of a GaN/AlGaN multiple-quantum-well active region with emission wavelength near 360 nm. The LED devices were 100 mm in diameter with a top p-electrode and a lateral n-contact. The light was extracted through the transparent AlN substrate. Crystal IS has started supplying research quantities of high-quality AlN substrates and has demonstrated dislocations densities of less than 1000 cm-2. AlN substrates offer a very high thermal conductivity (~320 W/m-K), which is important for high power operation of light emitting devices. They also provide good lattice matching particularly for AlGaN active regions with high Al concentrations as required for deep-UV LEDs with emission wavelengths below 300 nm. Non-polar substrate orientations are also available which may allow improvements in the quantum efficiency of nitride-semiconductor LED’s and laser diodes.

PR contact

Linda Jacobson, Manager, Communications & Marketing
PARC
+1-650-812-4035