Growth of High-Hole Mobility Stable ST12-Ge Thin Film on Si Substrate for Developing Metal-Oxide–Semiconductor (MOS) Devices

Abstract

The current work investigates the growth of high-hole mobility ST12-Ge thin film (5.85 nm) on Si substrate for its applications in MOS devices. Micro-Raman study indicates the generation of 3.73 GPa induced compressive stress in such ST12-Ge films and the absorption spectroscopy results confirm a direct bandgap of 0.69 eV and indirect bandgaps of 0.582, 0.634, 0.636, and 0.638 eV. The p-type carrier concentration and room temperature Hall mobility of the film are measured to be $4.49\times 10^{{18}}$ cm $^{-{3}}$ and $1.33\times 10^{{4}}$ cm2V $^{-{1}}$ s $^{-{1}}$ , respectively. C–V measurements of the fabricated Pt/ZrO2/ST12-Ge/n-Si MOS devices indicate a highly effective dielectric constant of 16.4 for ZrO2 with an effective oxide thickness (EOT) of ~4.09 nm along with the formation of a good ZrO $_{{2}}{}$ /ST12-Ge interface of trap density $2.76\times 10^{{11}}$ cm $^{-{2}}$ eV $^{-{1}}$ . The I–V characteristics exhibit a low leakage current density of $1.57\times 10^{-{2}}$ A/cm2 at +2 V and an insignificant stress-induced leakage current (SILC) at −5 V for $10^{{4}}$ s. Therefore, the overall study confirms the formation of a robust ST12-Ge film and ZrO2/ST12-Ge interface, which is suitable for developing CMOS devices with high channel mobility.