Interface studies of ALD-grown metal oxide insulators on Ge and III–V semiconductors (Invited Paper)

Atomic layer deposited (ALD) HfO2/GeOxNy/Ge(1 0 0) and Al2O3/In0.53Ga0.47As(1 0 0) − 4 × 2 gate stacks were analyzed both by MOS capacitor electrical characterization and by advanced physical characterization to correlate the presence of electrically-active defects with chemical bonding across the insulator/channel interface. By controlled in situ plasma nitridation of Ge and post-ALD annealing, the capacitance-derived equivalent oxide thickness was reduced to 1.3 nm for 5 nm HfO2 layers, and mid-gap density of interface states, Dit = 3 × 1011 cm−2 eV−1, was obtained. In contrast to the Ge case, where an engineered interface layer greatly improves electrical characteristics, we show that ALD-Al2O3 deposited on the In0.53Ga0.47As (1 0 0) − 4 × 2 surface after in situ thermal desorption in the ALD chamber of a protective As cap results in an atomically-abrupt and unpinned interface. By avoiding subcutaneous oxidation of the InGaAs channel during Al2O3 deposition, a relatively passive gate oxide/III–V interface is formed.