It can not be built in an intelligent manner. The two different electrodes are built separately using the "Atomic Manipulator" and they are combined together by hand. You could try to build it by the following outlined steps:
1) build a highly doped (n-type) bulk Si
1a) build a supercell of Si
1b) substitute one or more Si atoms with other element (i.e., the dopant). Of course, the impurity could be interstitial defects, in this situation, insert other element (dopant) into supercell of Si
2) build a two-probe system of n-type Si
2a). import the built n-type bulk Si into "Atomic Manipulator" and then build a two-probe system without conductor.
2b). export the configuration into a script file
2c). extract the configuration for left electrode by hand (i.e., copy&paste), meanwhile the configuration for the left surface layers should be also extracted by hand.
3) build a bulk Hg
3a) build a supercell of Hg. The area in the directions perpendicular to the transport direction should be same to the one of n-doped Si
4) build a two-probe system of Hg
4a). import the built Hg sample into "Atomic Manipulator" and then build a two-probe system without conductor.
4b). export the configuration into a script file
4c). extract the configuration for right electrode by hand (i.e., copy&paste), meanwhile the configuration for the right surface layers should be also extracted by hand.
5). manually combine those extracted in 2c) and 4c) steps
5a). put those obtained in 2c) and 4c) into a blank script file
5b). edit them to construct a two-probe configuration by hand. Especially, the distance between the left surface layer and the right surface layer should be chosen properly. Of course, this parameter need to be optimized.