Impact of La_2O_3 interfacial layers on InGaAs metal-oxide-semiconductor interface properties in Al_2O_3/La_2O_3/InGaAs gate stacks deposited by atomic-layer-deposition

摘要

We examine the electrical properties of atomic layer deposition (ALD) La_2O_3/InGaAs and Al_2O_3/ La_2O_3/InGaAs metal-oxide-semiconductor (MOS) capacitors. It is found that the thick ALD La_2O_3/InGaAs interface provides low interface state density (D_(it)) with the minimum value of ～3 × 10~(11) cm~(-2) eV~(-1), which is attributable to the excellent La_2O_3 passivation effect for InGaAs surfaces. It is observed, on the other hand, that there are a large amount of slow traps and border traps in La_2O_3. In order to simultaneously satisfy low D_(it) and small hysteresis, the effectiveness of Al_2O_3/La_2O_3/InGaAs gate stacks with ultrathin La_2O_3 interfacial layers is in addition evaluated. The reduction of the La_2O_3 thickness to 0.4 nm in Al_2O_3/La_2O_3/InGaAs gate stacks leads to the decrease in hysteresis. On the other hand, D_(it) of the Al_2O_3/La_2O_3/InGaAs interfaces becomes higher than that of the La_2O_3/InGaAs ones, attributable to the diffusion of Al_2O_3 through La_2O_3 into InGaAs and resulting modification of the La_2O_3/InGaAs interface structure. As a result of the effective passivation effect of La_2O_3 on InGaAs, however, the Al_2O_3/10 cycle (0.4 nm) La_2O_3/ InGaAs gate stacks can realize still lower D_(it) with maintaining small hysteresis and low leakage current than the conventional Al_2O_3/InGaAs MOS interfaces.