Molecular beam epitaxy and mobility enhancement of InxGa1-xAs/In0.52Al0.48As/InP HEMT structure

The InxGa_{1- x} As/In_0.52Al_0.48As/InP HEMT structures for low noise application were grown by MBE onto InP substrates. The influence of growth temperature profile, growth interruption, and structural parameters on the electrical characteristics have been systematically studied based on Hall measurements. The growth of the whole layer with interruption results in increase of mobility due to a improvement of interface abruptness. For the lattice-matched conditions maximum mobilities with values amounting to as high as 11,400 cm²/Vsec (300K), 50,300 cm²/Vsec (77K) were obtained near d_space=100Å and n_s=1.5x10¹² cm^-2. To improve the mobility characteristics, graded and pseudomorphic In _x Ga_{1- x} As were adopted as a channel layer. With the graded composition channel layer the mobilities of 11,800 cm²/Vsec (300K), 50,900 cm²/Vsec (77K) were obtained near d_spacer=30Å and n_s=2.5x10¹² cm^-2.