Simulation of the piezoelectric effect on the device characteristics of AlGaN/GaN insulated-gate heterostructure field effect transistors

The piezoelectric effect (PE) on the device characteristics due to lattice mismatch in the heterostructure was simulated by solving Poisson and Schrod inger equations self-consistently for GaN-based field effect transistors (F ET). By comparing the simulation results obtained with and without PE, we f ound the following. (1) PE shifts the threshold voltage (V-th) Of FET; this V-th shift widens the Bat region in transconductance-gate voltage (G(m)-V- gs) and cutoff frequency-gate voltage (f(T)-V-gs) characteristics. (2) G(m) is higher with PE than without PE, while f(T) values an nearly the same fo r both with and without PE. (3) The equilibrium two-dimensional channel ele ctron gas (2DEG) concentration (N-ch) increases considerably with PE. This 2DEG concentration greatly reduces the parasitic resistance between the gat e and the source/drain. We concluded that PE improves FET performance, and we determined the optimal FET structure with PE from the viewpoint of charg e control.