High-Performance InAlN/GaN MOSHEMTs Enabled by Atomic Layer Epitaxy MgCaO as Gate Dielectric

We have demonstrated high-performance InAlN/ GaN MOS high-electron-mobility-transistors (MOSHEMTs) with various channel lengths (
$L_{\mathrm {{ch}}}$
) of 85–250 nm using atomic-layer-epitaxy (ALE) crystalline Mg
_0.25
Ca
_0.75
O as gate dielectric. With a nearly lattice matched epitaxial oxide, the interface between oxide and barrier is improved. The gate leakage current of MOSHEMT is reduced by six orders of magnitude compared with HEMT. An OFF-state leakage current of
$3\times 10^{-13}$
A/mm, ON/OFF ratio of
$4\times 10^{12}$
, almost ideal subthreshold swing of 62 mV/decade, low drain current noise with Hooge parameter of
$10^{-4}$
, and negligible current collapse and hysteresis are realized. The 85-nm
$L_{\mathrm {ch}}$
MOSHEMT also exhibits good ON-state performance with
$I_{d\mathrm {max}}=2.25$
A/mm,
$R_{\mathrm{\scriptscriptstyle ON}}=1.3~\Omega \cdot \textrm {mm}$
, and
$g_{\mathrm {max}}=475$
mS/mm, showing that ALE MgCaO is a promising gate dielectric for GaN device applications.