Gate Characteristics of Enhancement-Mode Fully Depleted <i>p</i> -GaN Gate HEMT
Jiahui Sun, S. Mouhoubi, Marco Silvestri, Zheyang Zheng, Yat Hon Ng, Ji Shu, Kevin J. Chen, Gilberto Curatola
Abstract
The conventional <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -GaN in Schottky-type <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -GaN gate HEMTs is converted into an insulator-like <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -GaN, i.e., fully depleted <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -GaN in the reverse-biased Schottky junction under forward gate bias ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {GS}}$ </tex-math></inline-formula> ), by inadequate activation of Mg. Consequently, the gate current ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {G}}$ </tex-math></inline-formula> ) is reduced by 3–5 orders of magnitude at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {GS}}$ </tex-math></inline-formula> of 7-V over a temperature range of 25 °C–150 °C, compared with devices adopting conventional adequate activation. The fully depleted <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -GaN converts the current-balance-based forward <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {GS}}$ </tex-math></inline-formula> division in the conventional partially depleted <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -GaN gate stack, into thickness-based voltage division in <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${p}$ </tex-math></inline-formula> -GaN and AlGaN between gate and channel, which is like that in a MIS (metal-insulator-semiconductor) gate. As a result, the hole current through the Schottky junction is significantly reduced while the electron spillover current starts to dominate at high forward <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {GS}}$ </tex-math></inline-formula> . Besides, hot carriers are excluded from the forward gate breakdown mechanism.