Optimization of In_xGa_1-xAs/In_yAl_1-yAs high electron mobility transistor structures grown by solid-source molecular beam epitaxy

We report on the optimization of InP-based In_xGa_1-xAs/In_yAl_1-yAs pseudomorphic high electron mobility transistor (PHEMT) structures to achieve the highest possible two-dimensional-electron gas (2DEG) density and mobility. The layer structures are grown by solid-source molecular beam epitaxy with a valved phosphorus cracker cell. The single-side-doped PHEMT structure with a δ-doping concentration of 6×10¹² cm^-2 exhibits a 2DEG sheet density of 3.93×10¹² cm^-2 with a mobility of 11100 cm²/V s at 300 K. The double-side-doped PHEMT structure with a bottom δ-doping concentration of 1×10¹² cm^-2 and a top δ-doping concentration of 5×10¹² cm^-2 gives a 2DEG sheet density of 4.57×10¹² cm^-2 with a mobility of 10 900 cm²/V s at 300 K. The electrical, optical and structural properties of the PHEMT structures were characterized by Hall, photoluminescence, and x-ray diffraction measurements. © 2001 American Vacuum Society.