**3. Results and discussion**

introduced: one with 10 minutes sulfur passivation using (NH<sup>4</sup>

100 Design, Simulation and Construction of Field Effect Transistors

SO<sup>4</sup>

hafnium dioxide (HfO<sup>2</sup>

free Ge0.83Sn0.17/Ge interface.

at 250°C for 30 s in the N<sup>2</sup>

concentrated sulfuric acid (H<sup>2</sup>

(Cl<sup>2</sup>

room temperature (25°C) and the other one without sulfur passivation. After that, the samples were loaded into the atomic layer deposition (ALD) chamber immediately to avoid surface oxidation due to air exposure. Surface treatment was done using Trimethylaluminum (TMA) as precursor with pulse duration of 30 ms. This was followed by deposition of 3 nm-thick

**Figure 2.** (a) Low magnification XTEM image of an as-grown Ge0.83Sn0.17 sample showing the smooth GeSn surface. High magnification XTEM images of the Ge0.83Sn0.17 sample shows (c) the zoom-in view of smooth GeSn surface and (d) defect-

sors. The total ALD process duration including the pumping and venting steps is ~ 15 min. After that, 110 nm-thick tantalum nitride (TaN) was deposited using a reactive sputtering system. The metal gate was then patterned by photolithography and etched using chlorine

)-based plasma. A 10 nm-thick nickel (Ni) was then deposited using e-beam evaporator and the self-aligned Ni(GeSn) metallic contact was formed by rapid thermal annealing (RTA)

**Figure 3.** (a) (004) rocking scan of the as-grown sample shows both the Ge0.83Sn0.17 and Ge peaks. The well-defined GeSn peak indicates the good crystalline quality of the GeSn layer. The peak is relatively broader than the Ge peak because of the thin layer thickness of the GeSn layer. (b) (115) RSM showing that the Ge0.83Sn0.17 film is fully strained to the Ge (001) substrate. The substitutional Sn composition is calculated to be 17%. Device fabrication of Ge0.83Sn0.17 p-MOSFETs.

) at 250°C using Tetrakis (dimethylamido) hafnium and H<sup>2</sup>

)2

ambient. Finally, excess Ni was removed by selective wet etch using

) (96% by weight). The maximum processing temperature of

S solution (24% by weight) at

O as precur-
