Self-Aligned Gate Thin-Channel β-Ga2 O3 MOSFETs
2019 Device Research Conference (DRC)(2019)
摘要
Beta-phase gallium oxide
$(\beta-\mathrm{Ga}_{2}\mathrm{O}_{3})$
has shown promise as a next-generation wide-bandgap semiconductor for use in power electronics. It possesses a bandgap and expected critical field strength of ~4.8 eV and ~8 MV/cm, respectively, surpassing the same measured characteristics of GaN and SiC [1]. Early work has been successful in demonstrating lateral metal-oxide-semiconductor field-effect transistors (MOSFETs), predominately for depletion mode operation, with high critical field strength [2], high current density [3], and high breakdown voltage [4], [5]. One limitation of
$\beta-\mathrm{Ga}_{2}\mathrm{O}_{3}$
MOSFETs is source access resistance
$(\mathrm{R}_{\mathrm{S}})$
, the ungated region between source and gate, with sheet resistance
$(\mathrm{R}_{\mathrm{SH}})$
typically in the
$\mathrm{k}\Omega/\mathrm{sq}$
range. The
$\mathrm{R}_{\mathrm{S}}$
affects key device performance parameters such as transconductance
$(\mathrm{G}_{\mathrm{M}})$
and drain-current density
$(\mathrm{I}_{\mathrm{DS}})$
. Higher DC and RF performance can be expected from eliminating
$\mathrm{R}_{\mathrm{S}}$
by self-aligning the gate and source contacts. We present, for the first time, a self-aligned gate (SAG)
$\beta-\mathrm{Ga}_{2}\mathrm{O}_{3}$
MOSFET using a refractory metal gate-first design. MOSFET devices with
$2\mathrm{x}50\mu \mathrm{m}$
gate periphery,
$7.5\ \mu \mathrm{m}$
source-drain distance
$(\mathrm{L}_{\mathrm{SD}})$
and
$2\ \mu \mathrm{m}$
gate length
$(\mathrm{L}_{\mathrm{G}})$
were directly compared with and without the SAG features. MOSFETs with SAG show a substantial increase in
$\mathrm{G}_{\mathrm{M}}$
and
$\mathrm{I}_{\mathrm{DS}}$
, from ~2 mS/mm to ~14 mS/mm and ~10 mA/mm to ~45 mA/mm, respectively, up to
$\mathrm{V}_{\mathrm{GS}}=4$
V. Lastly, we report a laterally scaled device
$(2\mathrm{x}50\mu \mathrm{m})$
with
$\mathrm{L}_{\mathrm{SD}}=2.5\mu \mathrm{m}$
and
$\mathrm{L}_{\mathrm{G}}=2\mu \mathrm{m}$
, achieving high current density
$(\sim 140\mathrm{mA}/\mathrm{mm})$
, and high G
M
$(\sim 35\mathrm{mS}/\mathrm{mm})$
.
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关键词
beta-phase gallium oxide,wide-bandgap semiconductor,lateral metal-oxide-semiconductor field-effect transistors,critical field strength,breakdown voltage,source access resistance,drain-current density,source contacts,refractory metal gate,MOSFET devices,gate periphery,source-drain distance,self-aligned gate thin-channel MOSFET,power electronics,depletion mode operation,size 2.0 mum,voltage 4.0 V,size 2.5 mum,distance 7.5 mum,Ga2O3
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