Ga 2 O 3 Based Heterostructure FETs (HFETs) for Microwave …
221
4.2 III-Nitrides/β-Ga 2 O 3 Heterostructure
Higher output currents in GaN based HEMTs can be attributed to polarization induced
2DEG charge density in order of ~10
13 cm
−2 , and band-bending enabled conduction
band offset (CBO), at the hetero-interface, significantly affect carrier mobility apart
from intrinsic crystal properties. Earlier, growth and determination of band alignment
of the β-Ga 2 O 3 /AlN [41] and β-Ga 2 O 3 /GaN [42] heterostructures were reported. The
experimentally determined band offsets facilitated by the development of AlN/βGa 2 O 3 HEMTs, which is aided by a small in-plane lattice mismatch of 2.4% between
[201] β-Ga 2 O 3 and [0002] AlN.
Concerning RF performance of power devices, JFOM is important as given by
V BR f T ≤ E CRIC v sat /π . Due to a higher estimated value of critical electric field
(E CRIC ) up to 8 MV/cm and saturation velocity (v sat ) of 2.0 × 10
7 cm/s, β-Ga 2 O 3
HEMTs can significantly outperform their GaN counterpart as suggested in [22]. In
the recently reported AlN/β-Ga 2 O 3 HEMT [21], polarization induced higher 2DEG
density of 5.67 × 10
13 cm
−2 confined in the large CBO of 1.75 eV [41] was demonstrated. The highly scaled devices consist of 10 nm AlN barrier on 50 nm SI βGa 2 O 3 buffer, and gate length (L G ) of 50 nm, gate source (L GS ) of 0.25 μm and
gate-drain (L GD ) spacing of 1.3 μm. A small-signal high-frequency performance of
the device shows f T , and f MAX of 167 and 292 GHz, respectively. Large-signal highfrequency simulations at 10 GHz showed RF output power (P OUT ) of 2.91 W/mm
and power-added efficiency (PAE) of ~14%. The microwave and millimeter-wave
performance of the AlN/β-Ga 2 O 3 HEMT is shown in Fig. 10. These promising
results improves the prospect of β-Ga 2 O 3 HEMTs for potential microwave and
millimeter-wave applications.
In this work, we have focused on growth and development of β-Ga 2 O 3 heterostructure FETs, for microwave and millimeter-wave applications. Several other βGa 2 O 3 based transistors like MOSFETs [70–73] and metal–semiconductor FETs
(MESFETs) [74] have also been reported. In order to give a glimpse of these devices’
Fig. 10 Comparison of β-Ga 2 O 3 transistors RF performance, a output power density and gain
versus frequency and b cut-off frequency and maximum frequency of oscillation as a function of
the gate length (L G )
221
4.2 III-Nitrides/β-Ga 2 O 3 Heterostructure
Higher output currents in GaN based HEMTs can be attributed to polarization induced
2DEG charge density in order of ~10
13 cm
−2 , and band-bending enabled conduction
band offset (CBO), at the hetero-interface, significantly affect carrier mobility apart
from intrinsic crystal properties. Earlier, growth and determination of band alignment
of the β-Ga 2 O 3 /AlN [41] and β-Ga 2 O 3 /GaN [42] heterostructures were reported. The
experimentally determined band offsets facilitated by the development of AlN/βGa 2 O 3 HEMTs, which is aided by a small in-plane lattice mismatch of 2.4% between
[201] β-Ga 2 O 3 and [0002] AlN.
Concerning RF performance of power devices, JFOM is important as given by
V BR f T ≤ E CRIC v sat /π . Due to a higher estimated value of critical electric field
(E CRIC ) up to 8 MV/cm and saturation velocity (v sat ) of 2.0 × 10
7 cm/s, β-Ga 2 O 3
HEMTs can significantly outperform their GaN counterpart as suggested in [22]. In
the recently reported AlN/β-Ga 2 O 3 HEMT [21], polarization induced higher 2DEG
density of 5.67 × 10
13 cm
−2 confined in the large CBO of 1.75 eV [41] was demonstrated. The highly scaled devices consist of 10 nm AlN barrier on 50 nm SI βGa 2 O 3 buffer, and gate length (L G ) of 50 nm, gate source (L GS ) of 0.25 μm and
gate-drain (L GD ) spacing of 1.3 μm. A small-signal high-frequency performance of
the device shows f T , and f MAX of 167 and 292 GHz, respectively. Large-signal highfrequency simulations at 10 GHz showed RF output power (P OUT ) of 2.91 W/mm
and power-added efficiency (PAE) of ~14%. The microwave and millimeter-wave
performance of the AlN/β-Ga 2 O 3 HEMT is shown in Fig. 10. These promising
results improves the prospect of β-Ga 2 O 3 HEMTs for potential microwave and
millimeter-wave applications.
In this work, we have focused on growth and development of β-Ga 2 O 3 heterostructure FETs, for microwave and millimeter-wave applications. Several other βGa 2 O 3 based transistors like MOSFETs [70–73] and metal–semiconductor FETs
(MESFETs) [74] have also been reported. In order to give a glimpse of these devices’
Fig. 10 Comparison of β-Ga 2 O 3 transistors RF performance, a output power density and gain
versus frequency and b cut-off frequency and maximum frequency of oscillation as a function of
the gate length (L G )