Characteristics of In0.17Al0.83N/AlN/GaN MOSHEMTs with steeper than 60 mV/decade sub-threshold slopes in the deep sub-threshold region

Realization of steep sub-threshold slope (SS) transistors requires exploiting carrier transport mechanisms such as tunneling [1], and also alternative gate barrier materials (i.e. ferroelectric materials) with internal voltage gain [2]. Theoretical studies on piezoelectric barriers indicate that it is possible to achieve internal voltage amplification and steep SS in GaN MOSHEMTs by utilizing electrostriction in conjunction with piezoelectricity in AlN and InAlN [3] [4]. Less than 60 mV/decade SS was experimentally observed in GaN MOSHEMTs with InAlN barriers, in which the steep transition was tentatively correlated with the inhomogeneous distribution of polarization in the barrier [5]. However, steep SS were only observed at drain current (I_d) near nA/mm regimes, which leads to difficulties in interpretation of experiment data. Understanding of the mechanism of the steep SS in these devices is still unclear and needs more characterization and modeling. In this work we demonstrate InAlN/AlN/GaN MOSHEMTs with less than 60 mV/decade SS in deep sub-threshold regions (1E-8 A/mm and below) at room temperature (RT). Drain voltage and temperature dependent characteristics are provided with analysis for advancing our understanding of this phenomenon.