Role of Device Parameters in Optimizing 2DEG Charge Density in β-(AlxGa1−x)2O3/Ga2O3 HFET: An Analytical Approach

In this article, we present a physics-based analytical model for two-dimensional electron gas (2DEG) charge density (
${n} _{s}$
) in delta (
$\delta $
) doped
$\beta $
-(Al
_x
Ga
$_{{1} -{x}}$
)
₂
O
₃
/ Ga
₂
O
₃
heterostructure field-effect transistor (HFET). Subsequently, models for pinchoff voltage (
${V} _{\text {off}}$
), maximum 2DEG charge density (
${n} _{s\text {max}}$
) before the onset of parallel conduction, and maximum gate voltage (
${V} _{\text {gm}}$
) beyond which parallel conduction starts are also investigated.
${V} _{\text {gm}}$
is then used to calculate gate voltage swing (
${V}$
). Both complete and incomplete donor ionization (DI) are considered for model development. Incomplete DI shows a better match with experimental data than complete DI, thus predicting proper saturation of 2DEG charge density at high gate voltage. The effect of device parameters, such as Al composition (x), spacer layer thickness (
${d} _{s}$
), barrier layer thickness (
${d} _{b}$
), and
$\delta $
-doping density (
${n} _{\delta }$
) on
${n} _{s\text {max}}$
and
${V}$
, are studied using the developed models. Results show that thin spacer and high Al composition are essential for enhancement of
${n} _{s\text {max}}$
and
${V}$
. The obtained models for
${n} _{s\text {max}}$
and
${V} _{\text {off}}$
are also validated with the experimental results in the literature demonstrating a good accuracy. Thus, the proposed models will be quite useful to obtain enhanced 2DEG charge density by proper optimization of device parameters.