Large-signal microwave characteristics of resonant-tunneling high electron mobility transistors

The large-signal microwave characteristics of a resonant-tunneling high electron mobility transistor (RTHEMT) are investigated by experiments and simulations. A large number of harmonics, including extremely high-order harmonics with significant power, are observed in both the experiments and the simulations. The dependence of the output spectrum on input power shows that there is a critical input power for producing the extremely high-order harmonics, which is due to the bistability in the transfer characteristics. The origin of the bistability is explained by using an equivalent circuit model for the RTHEMT. Moreover, the dependence of the output power level of the low-order harmonics on input power was found to vary with the DC input voltage. This change of the dependence can be explained by examining the transfer characteristics. The DC transfer characteristics are the key to understanding the large-signal microwave characteristics peculiar to the RTHEMT.