The effect of ambipolarity puts TFET in an unfavorable position and restricts its superiority. The inclusion of a drain pocket at the drain-channel junction can prove it to be a realistic and successful way to remove the ambipolarity completely. In this paper, a 2-D analytical model has been presented for a Drain Pocket Double Gate Tunnel Field Effect Transistor (DP DG-TFET). The theoretical model agrees well with the previously reported data of Si DP DG-TFET. In this work, the SiGeSn heterostructure is used to achieve a lower bandgap and therefore to improve the tunnelling probability. A high ON current without any ambipolarity can be achieved from such type of DP DG-TFET.