Violet light-emitting diodes grown on crack-free AlGaN templates

Abstract

This study investigates the violet light-emitting diodes (LEDs) grown on crack-free AlGaN templates, which were prepared on GaN and AlN nucleation layers (NLs) over sapphire substrates by metal-organic chemical-vapor deposition using a two-step growth method. Symmetric and asymmetric x-ray diffraction patterns show that the LED structure grown on the AlGaN template with a GaN NL exhibits a better crystalline quality as compared to that with an AlN NL. When observed from the analyses of secondary-ion-mass spectroscopy and transmission-electron microscopy, it is found that the thickness and the indium composition in the InGaN wells of InGaN∕GaN multiquantum wells are slightly different at the growth temperatures of 720 and 750°C. In addition, the LEDs with GaN NL exhibit a narrower full width at half maximum of the excitonic peaks than those with AlN NL.