Solution-Driven HfLaOx-Based Gate Dielectrics for Thin Film Transistors and Unipolar Inverters

In this article, the preparation of HfLaO
_x
gate dielectric thin films by the spin coating method is proposed. The in-depth physical properties of the as-prepared HfLaO
_x
films were investigated as functions of annealing temperatures. Decided by the key performance indicators of current density, smooth surface, and areal capacitance of HfLaO
_x
films with different annealing temperatures, optimized performance parameters with annealing temperature 550 °C have been obtained. To verify the feasibility of HfLaO
_x
films as dielectric material, In
₂
O
₃
/HfLaO
_x
thin-film transistors (TFTs) have been fabricated and device characterizations have been carried out. As a result, it has been detected that the In
₂
O
₃
/HfLaO
_x
TFTs with optimized annealing temperature of 300 °C demonstrate superior electrical performance, including a high I
_ON
/ I
_OFF
of ~10
⁶
, a high μ
_FE
of 17.09 cm
²
V
^-1
s
^-1
, a low V
_TH
of 0.09 V, a small interfacial trap states ( D
_it
) of 1.94×10
¹²
cm
^-2
, and a small threshold voltage shift of 0.23 V under PBS test and 0.11 V under NBS test after 3600 s bias stress, respectively. To confirm TFTs' potential applications in logic circuits, a resistor-loaded inverter was integrated and the maximum voltage gain of 7.60 was demonstrated at an ultra-low operating voltage of 2.5 V. Current observations have indicated the great application prospects of solution-derived HfLaO
_x
-gated TFTs in low-cost and excellent performance electronic devices.