with one type of impurity right in the 2D layer itself (arising, for example, from the unintentional background impurities in the system) and the other type of impurity being a remote layer separated by a distance ‘$d_R$’ from the 2D electron layer. This minimal 2-impurity model is characterized by three independent parameters: $n_R$ and $d_R$, denoting respectively the 2D charged impurity density in the remote dopant layer separated by a distance $d_R$ from the 2D carriers, and $n_B$, the 2D impurity density corresponding to the unintentional background impurities in the 2D layer with $d=0$. It is easy to go beyond this minimal model and consider the remote impurities to be distributed over a finite distance (rather than simply being placed in a $\delta$-function like layer located at a distance $d_R$ from the 2D system) or assume the background impurities to be distributed three-dimensionally (rather than in a 2D plane at $d=0$), but such extensions do not modify any of our qualitative conclusion in the current paper as we have explicitly checked numerically. Also, we discuss our theory assuming a strict 2D model (with zero thickness) for the electron layer because the finite quasi-2D layer thickness has no qualitative effect on 