We explore a Si-Ge heterojunction doping-less tunnel FET on a thin undoped layer of silicon and germanium by means of calibrated simulations, using most of the charge plasma theory. The charge plasma theory is used to create the drain regions and source regions without the requirement for doping. Both the source regions and drain areas are generated by selecting metal electrodes with appropriate work functions and adopting the charge plasma theory. According to our investigations, the doping-less TFET performs quite similarly to its doped counterpart. Most importantly, any doping-less TFET provides comfort from problems caused by oscillations in random dopants. Furthermore, the high-temperature doping and annealing steps are not required in the fabrication process of a Si-Ge heterojunction doping-less Tunnel FETs, greatly lowering the thermal budget.