Investigations on Al₂O₃-Dielectric Wide-Gap Al_0.3Ga_0.7N Channel MOS-HFETs with Composite Al₂O₃/In Situ SiN Passivation

Abstract

3/in-situ SiN passivation and Al2O3 gate dielectric were investigated. 20 nm thick high-k Al2O3 was deposited using a non-vacuum ultrasonic spray pyrolysis deposition method. Comparative studies between an in-situ SiN-passivated Schottky-gate HFET (sample A) and a composite Al2O3/SiN-passivated MOS-HFET were made. Electrical and deep-UV sensing characteristics for devices with different gate-drain separations (LGD) of 6 and 14 μm were also studied. Improved device performance has been obtained for the present sample B (A) with LGD = 6/14 μm separately, including maximum drain-source current density (IDS, max) of 634.4/463.1 (421.8/301.1) mA/mm, maximum extrinsic transconductance (gm, max) of 25.2/17.9 (19.1/15.2) mS/mm, on/off-current ratio (Ion/Ioff) of 7.4 × 107/5.4 × 107 (4.5 × 105/5.4 × 104), two-terminal off-state gate-drain breakdown voltage (BVGD) of -420/-480 (-320/-390) V, and three-terminal on-state drain-source breakdown voltage of 310/380 (220/300) V at 300 K. Superior spectral responsivity of 885.6 A/W under 250-nm deep-UV radiation has also been achieved for the present MOS-HFET.

Investigations on Wide-Gap Al0.21Ga0.79N Channel MOS-HFETs With In0.12Al0.76Ga0.12N Barrier/Buffer and Drain Field-Plate

“…Similar polarization effects were maintained to provide appropriate comparison for the studied devices. Due to enhanced carrier confinement by the devised wide-gap In0.12Al0.76Ga0.12N or In0.12Al0.88N barrier/buffer, the obtained n2DEG values are higher than our previous works [15][16] and other InAlN/AlGaN device [25]. Moreover, the n and n-n2DEG product of sample B have been significantly enhanced due to the improved interfacial property in the In0.12Al0.76Ga0.12N/AlN/Al0.21Ga0.79N heterostructure.…”

“…Besides, the transfer length method (TLM) [28] was employed to measure the specific contact resistivity (ρc) and contact resistances (RC). ρc and RC were characterized to be 8.7 × 10 -6 (1.8 × 10 -5 ) Ω-cm 2 and 0.18 (0.26) Ω-mm for samples B1-B2 (A1), which are much lower than those wide-gap channel devices of our previous works [15][16]. It is mainly contributed by the devised n-GaN capping layer to greatly improve the source/drain ohmic contacts.…”

“…Consequently, enhanced gm, max performances have been achieved by the improved current densities in the present samples B1 and B2. The devised MOS-HFETs are superior to our previous woks [15][16] and other wide-gap-channel devices of gm, max = 16 mS/mm and IDS,max = 90 mA/mm [25], gm, max = 9 mS/mm and IDS, max = 350 mA/mm [29], IDS, max = 114 mA/mm [30], gm, max = 38 mS/mm and IDS, max = 635 mA/mm [31], IDS, max = 420 mA/mm [32], gm,max = 2.4 mS/mm and IDS, max = 13 mA/mm [33], and gm, max = 97.9 mS/mm and IDS, max = 473 mA/mm [34].…”

“…are needed. Our previous works have studied Si-doped AlGaN channel MOS-HFETs [15][16] showing depletion-mode operation and F --implanted AlGaN barrier MOS-HFET [17] exhibiting enhancement-mode characteristics. This work presents, for the first time, wide-gap Al0.21Ga0.79N channel MOS-HFETs with designs of In0.12Al0.76Ga0.12N barrier/buffer and drain field-plate (DFP).…”

Investigations on In₀.₁₂Al₀.₈₈N/AlN/AlₓGa₁−ₓN/In₀.₁₂Al₀.₈₈N MOS-HFETs With Symmetrically-Graded Wide-Gap Channel and Drain Field-Plate Design

“…GaN-based heterostructure field-effect transistors (HFETs) have been extensively studied for radio frequency (RF) power amplifier (PA), low noise amplifier (LNA), and high frequency switching applications [1][2][3][4][5][6] due to the advantageous properties of high electron mobility, high threshold electric field, and wide bandgap of GaN. Recently, with the growing demands for high-voltage operation in vehicle electronics [7] and renewable energy [8], AlGaN with higher Johnson's figure-of-merit (JFOM) [9] and Baliga's figure-of-merit (BFOM) [10] has been used as the channel recipe for metal-oxide-semiconductor HFETs (MOS-HFETs) [11][12][13][14][15]. As compared to GaN channel devices, the wide-gap AlGaN channel devices have demonstrated improved high-voltage power switching performance.…”