EKC2023

[P25-EI]Optimization of Gate-Head-Top/Bottom Lengths of AlGaN/GaN High-Electron-Mobility Transistor with Gate-Recessed Structure toward High Power Operation: A Simulation Study

Not scheduled

20m

Poster Poster(Wed)

Speaker

Mr Woo-Seok Kang (Dongguk University)

Description

In this study, we propose an optimized gate electrode structure of AlGaN/GaN high-electron-mobility transistors (HEMTs), improving 109.71% in breakdown voltage as compared to the basic T-gate structure. First, we varied the gate-head lengths of the basic T-gate HEMT. The length of gate-head-top (L_(Gate-Head-Top)) and gate-head-bottom (L_(Gate-Head-Bottom)) of the basic T-gate HEMT were 0.6 μm and 0.8 μm, respectively. The L_(Gate-Head-Top) and L_(Gate-Head-Bottom) were symmetrically extended by 0.2 μm step up to 1.6 μm and 1.8 μm, respectively. As compared to the basic T-gate HEMT, the breakdown voltage of the gate-head extended structure was improved due to the redistribution of the electric field concentrated in the drain-side gate edge. However, the frequency characteristics such as cut-off frequency (fT) and maximum frequency (fmax) were deteriorated as the area of the gate electrode increased. In order to minimize the degradation of frequency characteristics, we additionally employed the gate-recessed for the gate-head extended HEMT, as it attributes better transconductance by reducing the distance between the gate electrode and channel layer. The 25-nm-thick AlGaN barrier layer was thinned down to 13 nm by 3 nm step to form the gate-recess structure. In order to secure the reliability of the simulation, we matched the simulated data of the basic T-gate HEMT with the measured data of the fabricated device before the comparative analysis. Thereafter, to optimize the geometrical parameters of the gate electrode structure, we analyzed the DC and RF characteristics. Through the comparative analysis of the gate-head extended structures, the breakdown voltage of 1.0-μm-long gate-head extended structure was the highest. When compared to the basic T-gate HEMT, although the breakdown voltage of the 1.0-μm-long gate-head extended structure was improved by 52.05%, the fT and fmax were severely deteriorated by 30.55% and 39.70%, respectively. Meanwhile, the degradation of the frequency characteristics was significantly reduced with the 6-nm-depth gate-recessed structure of the 1.0-μm-long gate-head extended HEMT. As compared to the basic T-gate HEMT, the fT and fmax were decreased by only 19.96% and 8.94%, respectively, while the breakdown voltage was increased by 109.71%.
Through these results, we propose an optimized AlGaN/GaN HEMT with 1.0-μm-long gate-head extension along with the application of 6-nm-depth gate-recessed structure, while considering the trade-off between the DC and RF characteristics. Consequently, the proposed gate structure of HEMT with higher breakdown voltage, can be a promising candidate for high-power operation.

References

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