Normally-OFF AlGaN/GaN MIS-HEMTs With Low RON and Vth Hysteresis by Functioning In-situ SiNx in Regrowth Process

Normally-off AlGaN/GaN MIS-HEMTs with a high threshold voltage (
$\text{V}_{\text {th}}$
) more than 2.5 V and a low on- resistance of
$5.5\Omega \cdot $
mm have been achieved by an improved regrowth technique with
in-situ
SiN
_x
passivation. A thin-barrier heterojunction was used to decrease the two-dimensional electron gas (2DEG) underneath the gate, then regrown Al
_0.2
Ga
_0.8
N and
in-situ
SiN
_x
were applied to recover 2DEG at the access regions and reduce contact resistance. The O
₃
-based Al
₂
O
₃
and HfO
₂
were employed to cover the recessed-gate with low channel sheet resistances by atomic layer deposition. The other hybrid MIS-HEMT with
in-situ
SiN
_x
gate interlayer also enabled a normally-off operation with a
$\text{V}_{\text {th}}$
hysteresis lower than 30 mV. The damage-free recessed-gate structures with in- situ SiN
_x
as passivation and gate dielectric contribute to reducing surface scattering and interface states, resulting in a high
$\text{V}_{\text {th}}$
uniformity and channel mobility, low on- resistance and
_th
hysteresis in normally-off GaN-based MIS-HEMTs.