An analytical current-voltage characteristics model for high electron mobility transistors based on nonlinear charge-control formulation

Consideration of the nonlinear variation of the sheet carrier concentration of the two-dimensional electron gas (2-DEG) with Fermi potential in the quasi-triangular potential quantum well of the HEMT (high electron mobility transistor) structure has led to a bias-dependent effective offset distance of the 2-DEG from the heterointerface. The inclusion of the variable 2-DEG offset distance allows model characterization of the charge-control mechanism in a more consistent manner, and with greater accuracy, than the conventional linear charge-control model does. On the basis of the nonlinear charge-control formulation, the authors developed an accurate analytical drain current-voltage characteristics model for HEMT devices. This model is valid over a very wide range of operation, extending from the near-subthreshold regime to the high parasitic MESFET conduction regime to the high parasitic MESFET conduction regime. This model also includes the broadening effect of the 2-DEG quantum well in the pinchoff regime, providing a more accurate description of the current saturation mechanism. The authors demonstrate the effectiveness and accuracy of this model by comparing measured and modeled DC characteristics of normally-on as well as normally-off HEMT devices. Furthermore, the simple analytical expressions make the model very suitable for computer-aided design applications in the analysis and design of high-frequency microwave and high-speed digital HEMT devices and integrated circuits