Characteristics of InxAl1-xN-GaN high-electron mobility field-effect transistor

GaN-based field effect transistors commonly include an Al_xGa_1-xN barrier layer for confinement of a two-dimensional electron gas (2DEG) in the barrier/GaN interface. Some of the limitations of the Al_xGa_1-xN-GaN heterostructure can be, in principle, avoided by the use of In_xAl_1-xN as an alternative barrier, which adds flexibility to the engineering of the polarization-induced charges by using tensile or compressive strain through varying the value of x. Here, the implementation and electrical characterization of an In_xAl_1-x-GaN high electron mobility transistor with Indium content ranging from x=0.04 to x=0.15 is described. The measured 2DEG carrier concentration in the In_0.04Al_0.96N-GaN heterostructure reach 4×10¹³ cm^-2 at room temperature, and Hall mobility is 480 and 750 cm²/V · s at 300 and 10 K, respectively. The increase of Indium content in the barrier results in a shift of the transistor threshold voltage and of the peak transconductance toward positive gate values, as well as a decrease in the drain current. This is consistent with the reduction in polarization difference between GaN and In_xAl_1-xN. Devices with a gate length of 0.7 μm exhibit f_t and f_max values of 13 and 11 GHz, respectively.