Interface study of high-k/InAs/n-GaSb MOSCAP structures

Interface properties of Al2O3, HfO2 and TiO2 of 5 nm on GaSb substrate passivated with 2nm InAs were studied and compared. The interface properties of Al2O3/InAs/n-GaSb and HfO2/InAs/n-GaSb structures are reported, but no interface characterization of TiO2/InAs/n-GaSb has been done till today. In this paper, the capacitance voltage (C-V) characteristic of Al2O3/InAs/n-GaSb, HfO2/InAs/n-GaSb and TiO2/InAs/n-GaSb MOSCAP structures were simulated using TCAD tool at 300K. Thereafter, interface trap density (Dit), threshold voltage (Vth), flatband voltage (Vfb) and surface potential (Φs) were obtained by C-V and compared. The Dit values for Al2O3/InAs/n-GaSb, HfO2/InAs/n-GaSb and TiO2/InAs/n-GaSb MOSCAP structures were determined by Termann method and found to be 3.38×10¹² cm⁻²eV⁻¹, 1.15×10¹² cm⁻²eV⁻¹ and 9.11×10¹¹ cm⁻²eV⁻¹ respectively. It is interesting to note that the Dit value reduces by 65% in case of HfO2/InAs/n-GaSb, whereas by 75% in case of TiO2/InAs/n-GaSb structure compared to Al2O3/InAs/n-GaSb structure. Furthermore, the TiO2/InAs/n-GaSb structure has insignificant threshold voltage variation and much less flatband voltage variation for different oxide thicknesses ranging from 5nm to 10nm.