We propose a scaling theory for single gate Al In Sb/In Sb high electron mobility transistors(HEMTs) by solving the two-dimensional(2D) Poisson equation. In our model, the effective conductive path effect(ECPE) is taken into account to overcome the problems arising from the device scaling. The potential in the effective conducting path is developed and a simple scaling equation is derived. This equation is solved to obtain the minimum channel potential Φdeff,minand the new scaling factor α to model the subthreshold behavior of the HEMTs. The developed model minimizes the leakage current and improves the subthreshold swing degradation of the HEMTs. The results of the analytical model are verified by numerical simulation with a Sentaurus TCAD device simulator. We propose a scaling theory for single gate Al In Sb / In Sb high electron mobility transistors (HEMTs) by solving the two-dimensional (2D) Poisson equation. In our model, the effective conductive path effect (ECPE) is taken into account to overcome the problems arising from the device scaling. The potential in the effective conducting path is developed and a simple scaling equation derived the developed model minimizes the leakage current and improves the subthreshold swing degradation of the HEMTs. The results of the analytical model are verified by numerical simulation with a Sentaurus TCAD device simulator.