Carrier density and mobility modifications of the two-dimensional electron gas due to an embedded AlN potential barrier layer in Al_xGa_(1-x)N/GaN heterostructures

摘要

The variations in the electronic properties of the two-dimensional electron gas (2DEG) in Al_xGa_(1-x)N/GaN heterostructures due to an AlN embedded spacer layer were investigated by using Shubnikov-de Haas (SdH) measurements. The carrier densities of the 2DEGs in the Al_(0.4)Ga_(0.6)N/AlN/GaN and the Al_(0.4)Ga_(0.6)N/GaN heterostructures, determined from the SdH data, were 8.75 X 10~(12) and 8.66 X 10~(12) cm~(-2), respectively. The electron carrier density and the mobility of the 2DEG in the Al_xN/GaN heterostructure with an AlN spacer layer were larger than those in the Al_xGa_(1-x)N/GaN heterostructure. The electronic subband energies, the wave functions, and the Fermi energies in the Al_(0.4)Ga_(0.6)N/AlN/GaN and Al_(0.4)Ga_(0.6)N/GaN heterostructures were calculated by using a self-consistent method taking into account spontaneous and piezoelectric polarizations. These present results indicate that the electronic parameters of the 2DEG occupying an Al_xGa_(1-x)N/GaN heterostructure are significantly affected by an AlN spacer layer, and they can help to improve the understanding of the applications of Al_xGa_(1-x)N/GaN heterostructures with AlN spacer layers in high-speed and high-power electronic devices.