Investigation of MgXZn1−XO/ZnO Heterojunction Thin-Film Transistors Fabricated Using Mist-Chemical Vapor Deposition

This study investigates heterojunction thin-film transistors (HTFTs) with Mg
$_{X}$
Zn
$_{1- {X}}\text{O}$
/zinc oxide (ZnO) heterojunctions deposited using mist chemical vapor deposition (mist-CVD). The X-ray diffraction patterns indicate that the mist-CVD deposited Mg
$_{X}$
Zn
$_{1- {X}}\text{O}$
/ZnO heterojunctions are
${c}$
-axis oriented. Different Mg/Zn ratios (0.1/0.9, 0.2/0.8, and 0.3/0.7) and Mg
$_{X}$
Zn
$_{1- {X}}\text{O}$
thickness (15, 30, 45 nm) are used to form the Mg
$_{X}$
Zn
$_{1- {X}}\text{O}$
/ZnO heterojunctions of HTFTs. The Mg
_0.3
Zn
_0.7
O (15 nm)/ZnO HTFT exhibits high field-effect mobility of 165.56 cm
²
V
⁻¹
s
⁻¹
and steep subthreshold slope (SS) of 106 mV/dec, but low ON-/OFF-current ratio and high gate leakage current. The Mg
_0.3
Zn
_0.7
O (45 nm)/ZnO HTFT shows the largest ON-/OFF-current ratio of
$8.4\times10$
⁸
and low gate leakage current of 19.4 pA (at
${V}_{G} =5$
V)/0.27 pA (at
${V}_{G} = -5$
V) but sacrifices the field-effect mobility and SS. The Mg
_0.3
Zn
_0.7
O (30 nm)/ZnO HTFT with the optimum electrical characteristics is used to estimate the stability. It is found that the Mg
_0.3
Zn
_0.7
O/ZnO HTFT is more stable than the ZnO thin-film transistor (TFT).