E-Mode AlN/GaN HEMTs on Si With 80.4% PAE at 3.6 GHz for Low-Supply-Voltage RF Power Applications

Enhancement-mode (E-mode) AlN/GaN high electron mobility transistors (HEMTs) with a 160-nm T- shape recessed gate on a silicon substrate were fabricated. The fabricated device has a <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {TH}}$ </tex-math></inline-formula> of +0.35 V, and shows a maximum drain current (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${I}_{\text {DMAX}}\text {)}$ </tex-math></inline-formula> of 1.58 A/mm, a low on- resistance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${R}_{\text {ON}}\text {)}$ </tex-math></inline-formula> of <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$1.8~\Omega \cdot $ </tex-math></inline-formula> mm, and a peak transconductance (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${G}_{\text {MMAX}}\text {)}$ </tex-math></inline-formula> over 580 mS/mm. A cut-off frequency (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}_{\text {T}}\text {)}$ </tex-math></inline-formula> of 85 GHz and a maximum oscillation frequency (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${f}_{\max }\text {)}$ </tex-math></inline-formula> of 75 GHz were obtained. Load pull continuous-wave (CW) power sweep measurement at 3.6 GHz demonstrated a peak power-added-efficiency (PAE) of 71.4% and a saturated output power density (<inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {out}}\text {)}$ </tex-math></inline-formula> of 0.70 W/mm at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {DS}}=6$ </tex-math></inline-formula> V. At 3.6 GHz pulsed wave (PW) power sweep at <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${V}_{\text {DS}}=6$ </tex-math></inline-formula> V the device demonstrated an 80.4% PAE and 0.5 W/mm associated <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">${P}_{\text {out}}$ </tex-math></inline-formula>. These results promises the great potential of E-mode AlN/GaN HEMTs with gate recess in the applications of low supply voltage RF power applications.