Static and transient characteristics of GaN power HFETs with low‐conducting coating

Abstract

We report on a design of GaN based HFET with a low‐conducting layer (LCL) coating. The LCL coating dramatically improves the electric field uniformity and increases the breakdown voltage. A major advantage is consistent control of the breakdown characteristics, which is expected to dramatically improve yield and reliability. Initial experimental studies demonstrated a three‐fold increase in the breakdown voltage compared with conventional HFETs. The LCL also leads to a much more uniform underlying channel depletion evidenced by a significantly lower HFET channel capacitance in the off state for the HFET based RF switches. This results in a lower loss and higher isolation. Another advantage is a faster transient enabled by LCL, which should improve efficiency and reduce loss for power HFET switches.(© 2014 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

New Approaches to Realizing High Power Nitride Based Field Effect Transistors

“…Our results exploring the PC channel and LCL designs [1][2][3][4][5][6] show that these design innovations enable a sharp increase in the breakdown voltage, a large enhancement of the cutoff frequency, a better device stability and smaller spreading of the device parameters for higher yield, improved manufacturability, and smaller self-heating due to a lower thermal impedance.…”

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We report on several key innovations to enable high performance/high reliability of nitride based FETs that include (1) the use of Perforated Channel (PC) design; (2) surface application of Low Conducting Layers (LCLs); (3) the combination of these two approaches (for achieving the ultimate power performance at the highest switching frequencies with minimum losses); (4) novel device geometries (combining the best features of lateral and vertical devices for normally-off transistors); (5) improved control of self-heating and better heat dissipation. We also review our recent results exploring the PC channel and LCL designs [1][2][3][4][5][6]. Experimental and simulation results reported in [1-6] demonstrated a sharp increase in the breakdown voltage, a large enhancement of the cutoff frequency, a better device stability and smaller spreading of the device parameters for higher yield, improved manufacturability, and smaller self-heating due to a lower thermal impedance.

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(Invited) New Approaches for Shrinking the Performance Gap for GaN Power Devices

“…However, these approaches do not address a major problem of controlling sporadic surface charges in the gate to-drain spacing, which negatively affect the electric field uniformity and reproducibility of power GaN-based HFETs. The novel approach demonstrated in (49) solves this problem and improves electric field uniformity by adding the low-conducting layer (LCL) coating in the gate-to-drain region of GaN based HFETs (see Fig. 21).…”

(Invited) Physics of GaN High Electron Mobility Transistors

“…A better device uniformity results in a higher yield, and improved manufacturability. This design could be combined with the application of Low Conducting Layers (LCLs) (19,20,21) to control the properties and stability of ungated surfaces and dramatically increase the breakdown voltage. Figure 11 illustrates a better uniformity in the electric field distribution and the related sharp increase in the breakdown voltage achieved due to the LCL in the gate-to-drain spacing.…”