The paper deals with trap effects in InAlN/AlN/GaN and AlGaN/AlN/GaN high electron mobility transistor structures using frequency dependent conductance and High-Low frequency capacitance analysis. We performed a comparative study on electrical characteristics of electron devices. Capacitance-voltage characteristics revealed hysteresis with a voltage shift that was attributed to the accumulation of charges at the InAlN/AlN and AlGaN/AlN heterointerfaces. Using a simple extraction method, a rather low density of trapped charges is evaluated. On the other hand, bias and frequency dependent measurements are carried out in the vicinity of threshold voltage to determine the interface trap density D-it, trap time constant tau(it) and trap state energy position E-T. It is found that device with InAlN barrier exhibits high trap state densities in the range of 10(12)-10(14) cm(-2)eV(-1), approximately one order of magnitude larger than with AlGaN barrier. (C) 2017 Elsevier B.V. All rights reserved.