Effects of cap layer on 2DEGs in InN-based heterostructures

This paper describes the effects of cap layer on sheet carrier concentration and mobility of two dimensional electron gases (2DEGs) in InN-based InN/InGa(Al)N/InN heterostructures. Addition of a InN cap layer in InGa(Al)N/InN heterostructure leads to a very interesting dependence of 2DEGs. The sheet carrier concentration decreases and mobility increases with increase of the InN cap layer thickness. The calculated values of sheet carrier concentration are found to be decreased from 6 × 10¹³ to 1.2 × 10¹³ cm^-2 with increase of the cap layer thickness from 1 to 60 nm for a 10 nm barrier. The 2DEGs mobilities are found to be around 3.3 × 10³, 3.5 × 10³, and 4.8 × 10⁴ cm²V^-1sce^-1, respectively, without, with 10 nm and 100 nm cap layer. The cap layer also enhances the peak drift velocity. The above calculated results indicate that addition of cap layer is very promising for the fabrication of high performance HEMTs.