Effects of AlN interlayer on the transport properties of nearly lattice-matched InAlN/GaN heterostructures grown on sapphire by pulsed metal organic chemical vapor deposition

Abstract

The effects of AlN interlayer thickness on the transport properties of nearly lattice-matched InAlN/GaN heterostructures grown on sapphire substrates by pulsed metal organic chemical vapor deposition have been studied in detail. A very high electron mobility of approximately 1425cm2/Vs at room temperature and 5308cm2/Vs at 77K together with a two dimensional electron gas (2DEG) density of 1.75×1013cm−2 were obtained for nearly lattice-matched InAlN/GaN heterostructures with an optimum ∼1.2nm thick AlN interlayer. For comparison, InAlN/GaN heterostructure without AlN interlayer exhibited a 2DEG density of 1.61×1013cm−2 with low electron mobility of 949 and 2032cm2/Vs at room temperature and 77K, respectively. This significant enhancement of electron mobility is mainly attributed to an optimized AlN interlayer, which provides a smooth interface between InAlN barrier layer and GaN buffer layer and hence remarkably reduces the alloy disorder scattering by suppressing carrier penetration from the GaN channel into the InAlN barrier layer. Simultaneously, a best surface morphology with a root mean square roughness value of 0.24nm is obtained with the optimized AlN interlayer.