Materials Design on the Origin of Gap States in a High-κ/GaAs Interface

摘要

Given the demand for constantly scaling microelectronic devices to ever smaller dimensions, a SiO_2 gate dielectric was substituted with a higher dielectric-constant material, Hf(Zr)O_2, in order to minimize current leakage through dielectric thin film. However, upon interfacing with high dielectric constant(high-κ) dielectrics, the electron mobility in the conventional Si channel degrades due to Coulomb scattering, surface-roughness scattering, remotephonon scattering, and dielectric-charge trapping. III-V and Ge are two promising candidates with superior mobility over Si. Nevertheless, Hf(Zr)O_2/III-V(Ge) has much more complicated interface bonding than Si-based interfaces. Successful fabrication of a high-quality device critically depends on understanding and engineering the bonding conflgurations at Hf(Zr)O_2/III-V(Ge) interfaces for the optimal design of device interfaces. Thus, an accurate atomic insight into the interface bonding and mechanism of interface gap states formation becomes essential. Here, we utilize firstprinciple calculations to investigate the interface between HfO_2 and Ga As. Our study shows that As—As dimer bonding, Ga partial oxidation(between 3+ and 1+) and Ga— dangling bonds constitute the major contributions to gap states. These findings provide insightful guidance for optimum interface passivation.