Sub-10-nm Extremely Thin Body InGaAs-on-Insulator MOSFETs on Si Wafers With Ultrathin $\hbox {Al}_{2}\hbox {O}_{3}$ Buried Oxide Layers

We have demonstrated sub-10-nm extremely thin body (ETB) InGaAs-on-insulator (InGaAs-OI) nMOSFETs on Si wafers with Al₂O₃ ultrathin buried oxide (UTBOX) layers fabricated by direct wafer bonding process. We have fabricated the ETB InGaAs-OI nMOSFETs with channel thicknesses of 9 and 3.5 nm. The 9-nm-thick ETB InGaAs-OI n MOSFETs with a doping concentration (N_D) of 10¹⁹ cm^-3 exhibit a peak electron mobility of 912 cm²/V·s and a mobility enhancement factor of 1.7 times against the Si nMOSFET at a surface carrier density (N_s) of 3 ×10¹² cm^-2. In addition, it has been found that, owing to Al₂O₃ UTBOX layers, the double-gate operation improves the cutoff properties. As a result, the highest on-current to the lowest off-current (I_on/I_off) ratio of approximately 10⁷ has been obtained in the 3.5-nm-thick ETB InGaAs-OI nMOSFETs. These results indicate that the high-mobility III-V nMOSFETs can be realized even in sub-10-nm-thick channels.