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Beta-AlGaO/Ga2O3 Tri-Gate MOSHEMT with 70GHz fT and 55GHz fmax

Noor Jahan Nipu, Chinmoy Nath Saha, Uttam Singisetti

TL;DR

This work targets high-frequency, high-power operation in β-Ga2O3 devices by implementing tri-gate AlGaO/GaO MOSHEMTs with a thin Al2O3 gate dielectric grown on ozone-MBE–grown heterostructures. The devices feature 1 μm fins with LG=155 nm, a 5 nm gate oxide, and 100 nm Al2O3 passivation, achieving a record Ga2O3 RF performance of $f_T=70\ \mathrm{GHz}$ and $f_{MAX}=55\ \mathrm{GHz}$, with a gate-length–normalized f_T of $10.85\ \mathrm{GHz\cdot\mu m}$. The combination of improved electrostatics from the tri-gate geometry, a robust 2DEG at the heterointerface, and effective trap passivation yields low gate leakage and stable pulsed/RF operation, positioning tri-gate AlGaO/GaO devices as a promising platform for future RF power electronics. These results demonstrate the viability of Ga2O3-based tri-gate MOSHEMTs for high-frequency, high-power applications.

Abstract

We report Beta-AlGaO/Ga2O3 tri-gate heterostructure MOSHEMTs incorporating a thin 5 nm Al2O3 gate oxide layer for improved gate control and reduced leakage. The devices were fabricated on AlGaO/GaO heterostructures grown by ozone MBE on Fe-doped Ga2O3 (010) substrates. The tri-gate MOSHEMTs, with 1 micron-wide fins and Lg=155 nm, exhibit a peak current-gain cut-off frequency fT=70 GHz and a power-gain cut-off frequency fMAX=55 GHz.The fT.L product of 10.85 GHz-micron is the highest among reported Ga2O3 FETs to date. The devices show Vth =-0.5 V, an on/off ratio 10^6 I=80 mA/mm, a peak gm=60 mS/mm, and a low gate leakage current of 10^(-10) mA/mm at Vgs=0.5 V. Passivation with a 100 nm ALD Al2O3 layer effectively removes DC/RF dispersion and maintains stable operation under pulsed IV and repeated RF measurements. These results demonstrate the potential of tri-gate AlGaO/GaO MOSHEMTs for next-generation high-frequency and high-power applications.

Beta-AlGaO/Ga2O3 Tri-Gate MOSHEMT with 70GHz fT and 55GHz fmax

TL;DR

This work targets high-frequency, high-power operation in β-Ga2O3 devices by implementing tri-gate AlGaO/GaO MOSHEMTs with a thin Al2O3 gate dielectric grown on ozone-MBE–grown heterostructures. The devices feature 1 μm fins with LG=155 nm, a 5 nm gate oxide, and 100 nm Al2O3 passivation, achieving a record Ga2O3 RF performance of and , with a gate-length–normalized f_T of . The combination of improved electrostatics from the tri-gate geometry, a robust 2DEG at the heterointerface, and effective trap passivation yields low gate leakage and stable pulsed/RF operation, positioning tri-gate AlGaO/GaO devices as a promising platform for future RF power electronics. These results demonstrate the viability of Ga2O3-based tri-gate MOSHEMTs for high-frequency, high-power applications.

Abstract

We report Beta-AlGaO/Ga2O3 tri-gate heterostructure MOSHEMTs incorporating a thin 5 nm Al2O3 gate oxide layer for improved gate control and reduced leakage. The devices were fabricated on AlGaO/GaO heterostructures grown by ozone MBE on Fe-doped Ga2O3 (010) substrates. The tri-gate MOSHEMTs, with 1 micron-wide fins and Lg=155 nm, exhibit a peak current-gain cut-off frequency fT=70 GHz and a power-gain cut-off frequency fMAX=55 GHz.The fT.L product of 10.85 GHz-micron is the highest among reported Ga2O3 FETs to date. The devices show Vth =-0.5 V, an on/off ratio 10^6 I=80 mA/mm, a peak gm=60 mS/mm, and a low gate leakage current of 10^(-10) mA/mm at Vgs=0.5 V. Passivation with a 100 nm ALD Al2O3 layer effectively removes DC/RF dispersion and maintains stable operation under pulsed IV and repeated RF measurements. These results demonstrate the potential of tri-gate AlGaO/GaO MOSHEMTs for next-generation high-frequency and high-power applications.
Paper Structure (4 sections, 3 figures)

This paper contains 4 sections, 3 figures.

Table of Contents

  1. Introduction
  2. Device Structure and Fabrication
  3. Results and Discussion
  4. Conclusion

Figures (3)

  • Figure 1: (a) Epitaxial layer stack of trigate HFET, (b) Cross-section of final fabricated device structure,(c) Magnified top view SEM image of a fabricated device showing I gate device with dimensions LSG/LG/LGD = 0.455 $\mu$m, 0.155 $\mu$m, 1.95 $\mu$m and the FIN cross section. (d) Simulated energy band diagram and electron concentration profile.vaidya2021enhancement.
  • Figure 2: (a) ID-VDS output curve at room temperature showing peak ID= 80 mA/mm with RON=28.2$\mathrm{\Omega}$ mm at VGS=1V and VDS=5V, (b) ID-VGS transfer curve showing peak gm 60 mS/mm,(c) Semilog transfer curve showing ID and IG showing gate leakage current lower 10-10 mA/mm at VGS=0.5 V (d) Output curve at T = 50 K showing peak ID= 110 mA/mm with RON = 16 $\Omega$.mm at VGS= 1 V (e) ID-VGS transfer curve at T= 50 K showing peak gm$\approx$80 mS/mm, (f) Pulsed ID-VDS measurements after 100 nm Al2O3 passivation (and repeated RF tests): no current collapse for VGS=-2 V and for the double-pulse case VGS,Q =-2 V, VDS,Q=5V, indicating effective trap passivation on fin sidewalls and surface.
  • Figure 3: Small-signal RF performance at VGS=1 V and VDS=15 V for LG=0.155 $\mu$m(a) Measured and simulated h21 versus frequency showing fT=70 GHz. Inset: RF small signal model developed in ADS, with measured gm and CGS adjusted within 30%. (b) Measured unilateral power gain (U) and MAG/MSG versus frequency showing fMAX=55 GHz. (c) fT.LG product with LG compared with other reported $\beta$-Ga2O3 FETs, showing the highest fT.LG product (10.85 GHz-$\mu$m) achieved in this work. (d) fT versus LG benchmark plot of our devices compared to other $\beta$-Ga2O3 RF FETs and AlGaN/GaN HEMTs.