Record-High BVDS
p-Channel P++-GaN/P-GaN/GaN/AlN/Al0.3Ga0.7n MOS-HFETs with Drain Field-Plate Design
Authors: Lee Ching-Sung , Ke Jian-Hong , Liao Zhong-Liang , Cai Yu-Syuan , Yang Yong-Han , Jian-Hong Ke 
Published: December 2024

This work reports record-high three-terminal on- state drain-source breakdown voltage (BVDS
) of -735 V, superior on/off current ratio (Ion
/Ioff
) of 2 × 106, and improved device performance of the p-channel p++- GaN/p-GaN/GaN/AlGaN metal-oxide-semiconductor hetero-structure field-effect transistors (MOS-HFETs) with drain-field plate (DFP) design. A reference MOS-HFET without DFP was fabricated and studied in comparison. High-k, wide-gap Al2O3 was deposited as the gate oxide and surface passivation by using a non-vacuum ultrasonic spray pyrolysis deposition (USPD) technique. Atomic force microscope (AFM), transmission electron microscope (TEM), X-ray photoelectron spectroscopy (XPS), and capacitance-voltage (C-V) measurement were also performed to characterize the material and interface quality of the MOS-gate design. The present p-channel MOS-HFET design is promising for high-voltage complementary power-switching circuit application.

The schematic device structures of the present p++-GaN/ p-GaN/GaN/AlN/Al0.3Ga0.7N MOS-HFETs without/with DFP (samples A/B) are shown in Fig. 1(a). The epitaxial layers for both samples were grown on a Si substrate by using a low-pressure metal-organic chemical vapor deposition (LP-MOCVD) system. The related schematic energy-band diagram was shown in Fig. 1(b), illustrating the formation of 2DHG by the heterostructural design. Standard lift-off and photolithography were applied to the device fabrication for the present sample with (without) DFP design. The AFM photos shown in Figs. 2 (a)-(c) compared the surface roughness after dry-etching, after the TMAH treatment, and after the further deposition of Al2O3 by USPD. The cross-sectional TEM photo of the Al2O3 oxide was shown in Fig. 2 (d). The XPS profile shown in Fig. 3 also verified the composition of the Al2O3 layer. Fig. 4 shows the C-V hysteresis measurement curves to confirm the improved interfacial quality by the Al2O3 passivation.

Figs. 5(a)-(b) show the typical IDS
-VDS
curves and the transfer IDS
/gm
-VGS
characteristics for the studied samples A and B at 300 K. The characterized three-terminal on- state drain-source breakdown voltage (BVDS
) andtwo-terminal off-state gate-drain breakdown voltage (BVGD
) were also compared in Fig. 6 and its inset. Due to the integrated device design as mentioned before, the present sample B (A) with (without) DFP has demonstrated superior maximum drain-source current density (IDS, max
) of -9.5 (-10.6) mA/mm at VDS
= 20 V, on/off current ratio (Ion
/Ioff
) of 2 × 106 (9.2 × 105), BVGD
of 710 (520) V, and BVDS
of -735 (-545) V, respectively. Enhanced gate modulation, improved current density, enhanced Ion
/Ioff
switching, and superior BVDS
and BVGD
performances have been successfully achieved. Comparisons of the IDS, max
vs. Ion/Ioff
benchmark of the present samples A and B with respect to other p- channel GaN-based devices were shown in Fig. 7. The present sample B has achieved the record-high BVDS
of - 735 V with superior Ion
/Ioff
ratio of 2 × 106.

The present p-channel GaN MOS-HFET designs with/without DFP have been successfully investigated. Through the integrated heterostructural/device designs, material/interface characterizations, and comparative device measurement, the present sample B has demonstrated superior performance with the highest BVDS
record, so far. It is beneficial to high-voltage complementary power-switching IC applications.

Figure 1