Thermionic Field Emission in the Lifetime Estimation of p-GaN Gate HEMTs

The current transport mechanism at metal gate/p-GaN interface in p-GaN HETMs has been investigated. Space Charge Limited Current (SCLC) well describes the behaviour of current density (J<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub>) at lower applied bias (V<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {G}} \lt 6$ </tex-math></inline-formula> V), while Thermionic Field Emission (TFE) represents the dominant current mechanism at higher V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub>. Then, p-GaN gate reliability was investigated by time-to-failure (TTF) analysis carried out at constant positive V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub>. In particular, the devices’ lifetime as function of the applied V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> was described considering the J<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub>-V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> dependence according the TFE model. In this way, a maximum V<sub xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">G</sub> for 10-year lifetime (V<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$_{\text {Gmax}}^{{10}~\text {years}}$ </tex-math></inline-formula>) of 8.5 V has been estimated, significantly higher than that extracted by conventional E-model (7 V).