Ge metal-oxide-semiconductor devices with Al2O3/Ga2O3(Gd2O3) as gate dielectric

Ga2O3(Gd2O3) [GGO] 3.5 nm-thick, with an in situ Al2O3 cap 1.5 nm thick, has been directly deposited on Ge substrate without employing interfacial passivation layers. The equivalent oxide thickness (EOT) of the gate stack is 1.38-nm. The metal-oxide-semiconductor (MOS) capacitors using Al2O3/GGO as the gate dielectric have given capacitance–voltage characteristics with frequency dispersions of ∼4% at accumulation (10 kHz–1 MHz) and frequency dependent flat-band voltage shift (∼30 mV). The dielectric constant of the GGO remains at 14–15. Furthermore, the TiN/Al2O3/GGO/Ge pMOSFET with a gate length of 1 μm has given a saturation drain current density, a maximum transconductance and a field-effect hole mobility of 800 μA/μm, 423 μS/μm, and 300 cm2/V s, respectively.

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► Direct deposition of high-κ Ga2O3(Gd2O3) [GGO] on Ge without interfacial layers.
► Attainment of good thermal stability, high κ value (14–15), and sub-nm CET (∼0.96 nm) in GGO.
► High quality of GGO/Ge interface, evidenced by high Id, gm, and mobility in MOSFET.
► Excellent scalability of GGO, indicated by good dependence of MOSFET’s performance enhancement on CET reduction.