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

• Main Authors: Weichao Wang, Cheng Gong, Ka Xiong, K.C. Santosh, Robert M. Wallace, Kyeongjae Cho
• Format: Article
• Language: English
• Published: Elsevier 2015-09-01
• Series: Engineering
• Subjects: high-mobility device; high-κ/III-V interface; interfacial gap states; first-principle calculations
• Online Access: http://www.sciencedirect.com/science/article/pii/S2095809916300157

Given the demand for constantly scaling microelectronic devices to ever smaller dimensions, a SiO2 gate dielectric was substituted with a higher dielectric-constant material, Hf(Zr)O2, 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, remote-phonon scattering, and dielectric-charge trapping. III-V and Ge are two promising candidates with superior mobility over Si. Nevertheless, Hf(Zr)O2/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 configurations at Hf(Zr)O2/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 first-principle calculations to investigate the interface between HfO2 and GaAs. 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.