Study of p-GaN Gate HEMT with ALN Cap Layer

In this work, we present a p-GaN gate HEMT with a AlN cap layer and investigate the impacts of the different thicknesses of cap layers on the performances of p-GaN gate HEMTs using Silvaco TCAD. The transfer characteristics and gate forward breakdown characteristics are simulated, and the results show that devices with cap layer exhibit a higher threshold voltage (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text{TH}})$</tex> and gate forward breakdown voltage (<tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text{G-BD}}$</tex>) compared to the conventional p-GaN gate HEMT. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text{TH}}$</tex> and <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text{G-BD}}$</tex> of the device are positively correlated with the thickness of the AlN cap layer. The <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text{TH}}$</tex> of device with 5 nm AlN cap layer drift forward 0.6 v. And the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">$V_{\text{G-BD}}$</tex> of device with 5 nm AlN cap layer increases by 1.2 V. Based on the simulation results, we fabricate a device with a 5nm AlN cap layer and research its electrical characteristics, obtaining conclusions consistent with the simulation results.