Ge p-channel MOSFETS with La2O3 and Al2O3 gate dielectrics

We report on p-MOSFETs based on La₂O₃, Al₂O₃ and a mixture of both as high-k dielectric deposited by molecular beam epitaxy (MBE). Mobilities of about 140 cm²/Vs were achieved, which are 1.3 to 1.5 times larger than the universal hole mobility of Si/SiO₂. This demonstrates the potential advantage of La₂O₃-based Ge p-MOSFETs over Si devices. The negative threshold voltages V_T, which range between -0.2 and -1 V, make these gate stacks particularly attractive, given the fact that in several cases Ge p-MOSFETs exhibit an unwanted positive V_T shift.