Influence of the channel electric field distribution on the polarization Coulomb field scattering in AlGaN/AlN/GaN heterostructure field-effect transistors

Abstract

Using the Quasi-Two-Dimensional (quasi-2D) model, the current-voltage (I-V) characteristics of AlGaN/AlN/GaN heterostructure field-effect transistors (HFETs) with different gate length were simulated based on the measured capacitance-voltage (C-V) characteristics and I-V characteristics. By analyzing the simulation results, we found that the different polarization charge distribution generated by the different channel electric field distribution can result in different polarization Coulomb field scattering, and the difference of the electron mobility mostly caused by the polarization Coulomb field scattering can reach up to 1829.9 cm2/V·s for the prepared AlGaN/AlN/GaN HFET. In addition, it was also found that when the two-dimension electron gas (2DEG) sheet density is modulated by the drain-source bias, the electron mobility appears peak with the variation of the 2DEG sheet density, and the ratio of gate length to drain-source distance is smaller, the 2DEG sheet density corresponding to the peak point is higher

The influence of the channel electric field distribution on the polarization Coulomb field scattering in AlN/GaN heterostructure field-effect transistors

“…Therein, the solid lines are the electron mobility when the 2DEG sheet density is modulated by the drain-source bias (corresponding to zero gate-bias, V gs D 0 V), while the dashed lines are the low-field electron mobility (calculated in accordance with Ref. [10]) and the 2DEG sheet density is modulated by the gatesource bias (corresponding to V ds D 0.1 V).…”

“…The I -V characteristic calculation of AlN/GaN HFETs is based on a quasi-2D model and the calculation process is the same as described in Ref. [10]. The calculated I -V characteristics with different gate lengths are shown in Fig.…”

Influence of sapphire substrate thickness on the characteristics of AlGaN/AlN/GaN heterostructure field-effect transistors

“…However, the reliability of the HFETs is still challenging [3][4][5], and the polarization is very critical for the performance of GaN devices [6][7][8][9]. In AlGaN/AlN/GaN heterostructures, the GaN layer was always assumed to be strain free [10,11]. However, due to the lattice and thermal misfits between the substrate and the epilayers, there is residual strain in the GaN layer for the AlGaN/AlN/GaN heterostructures, which is one of the factors that affect the reliability of AlGaN/AlN/GaN HFETs [12,13].…”