Buck Converter Design

Hello,

I just started designing Power converters in Cadence Virtuoso. I am trying to implement an Open loop buck converter with the following specifications:

Vin - 5V

Vout - 1.8V

Fsw - 1MHz

Iload - 5A

L - 1uH, C - 200uF

I am using TSMC 250nm PDK and simulating my design using Spectre.

How do I design the power switching device for this design? In general, how do I implement a Power FET?

Thank You!