An AlGaN/GaN high-electron mobility transistor (HEMT) with a novel source-connected air-bridge field plate (AFP) is experimentally verified. The device features a metal field plate that jumps from the source over the gate region and lands between the gate and drain. When compared to a similar size HEMT device with a conventional field plate (CFP) structure, the AFP not only minimizes the parasitic gate to source capacitance, but also exhibits higher OFF-state breakdown voltage and one order of magnitude lower drain leakage current. In a device with a gate to drain distance of 6 μm and a gate length of 0.8 μm, three times higher forward blocking voltage of 375 V was obtained at VGS = −5 V. In contrast, a similar sized HEMT with a CFP can only achieve a breakdown voltage no higher than 125 V using this process, regardless of device dimensions. Moreover, a temperature coefficient of 0 V/K for the breakdown voltage is observed. However, devices without a field plate (no FP) and with an optimized conventional field plate (CFP) exhibit breakdown voltage temperature coefficients of −0.113 V/K and −0.065 V/K, respectively.

No abstract

No abstract

a) (b) Fig. 1. Schematic cross-section of GaN-MOS HEMTs (a) and atomic force microscope (AFM) image of the fully recessed gate region (b). Abstract-This paper reports for the first time a gate-recessed GaN-on-Silicon MOS-HEMT device with true normally-off operation and high breakdown voltage using a one step simultaneous oxidation/dissolving treatment by hybrid alkaline solution with hydrogen peroxide and potassium hydroxide. After 40-min wet etching at 95 ºC solution temperature, the Al 2 O 3 /GaN MOS-HEMT device features a true normally-off operation with a threshold voltage of 3 V, extracted by the linear extrapolation of the transfer curve. Combined with the three-terminal off-state breakdown voltage up to 1492 V for the device with 28 μm gateto-drain distance, this technique manifests an easy, stable and low cost approach for the commercialization of normally-off GaN power devices.

A novel structure of AlGaN/GaN Schottky barrier diode (SBD) featuring electric field optimization techniques of anode-connected-field-plate (AFP) and magnesium-doped p-type buried layer under the two-dimensional electron gas (2DEG) channel is proposed. In comparison with conventional AlGaN/GaN SBDs, the magnesium-doped p-type buried layer in the proposed structure can provide holes that can help to deplete the surface 2DEG. As a result, surface field strength around the electrode edges is significantly suppressed and the electric field along the channel is distributed more evenly. Through 2D numerical analysis, the AFP parameters (field plate length, LAFP, and field plate height, TAFP) and p-type buried layer parameters (p-type layer concentration, NP, and p-type layer thickness, TP) are optimized to achieve a three-equal-peak surface channel field distribution under exact charge balance conditions. A novel structure with a total drift region length of 10.5 μm and a magnesium-doped p-type concentration of 1 × 1017 cm−3 achieves a high breakdown voltage (VB) of 1.8 kV, showing 5 times improvement compared with the conventional SBD with the same device dimension.