Schottky Barrier Gate N-Polar GaN-on-Sapphire Deep Recess HEMT With Record 10.5 dB Linear Gain and 50.2% PAE at 94 GHz
Emre Akso, Henry Collins, Kamruzzaman Khan, Boyu Wang, Weiyi Li, Christopher Clymore, Emmanuel Kayede, Wenjian Liu, Tanmay Chavan, Robert Hamwey, Nirupam Hatui, Matthew Guidry, Brian Romanczyk, S. Keller, Umesh K. Mishra
Abstract
In this letter, we report on Schottky barrier (SB) gate N-Polar GaN-on-sapphire deep recess high-electron-mobility transistors (HEMTs) with excellent dc, small signal and large signal performance. A device with a gate length of 77 nm demonstrates a very high extrinsic dc transconductance ( <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$g_{m}$ </tex-math></inline-formula> ) of 917 mS/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">$V_{\mathbf {D}}$ </tex-math></inline-formula> of 3 V, nearly twice as much as prior N-Polar GaN metal-insulator-semiconductor (MIS) HEMTs, with a low gate current of below <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$40~\mu \text{A}$ </tex-math></inline-formula> /mm up to <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$+1~V_{\mathbf {G}}$ </tex-math></inline-formula> . For the same device, the peak intrinsic RF <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$g_{m}$ </tex-math></inline-formula> is 1.17 S/mm. A device with a 50 nm gate length demonstrates the highest N-Polar deep recess HEMT peak <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{T}$ </tex-math></inline-formula> of 176 GHz and peak <inline-formula xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink"> <tex-math notation="LaTeX">$f_{\mathbf {MAX}}$ </tex-math></inline-formula> of 307 GHz. Biased at 10 V and 0.25 A/mm (class-AB), the 77 nm gate length device exhibits a record 94 GHz large signal performance with a linear gain of 10.5 dB, 50.2% peak power-added efficiency (PAE) with 2.8 W/mm power and 3.2 W/mm peak power with 46.3% PAE and 6.1 dB compressed gain. The outstanding large signal performance on low-cost sapphire substrate is very attractive and it paves the way for the next generation high-efficiency wireless communication systems.