Potential solution-induced HfAlO dielectrics and their applications in low-voltage-operating transistors and high-gain inverters

Abstract

Recently, much attention has been paid to the investigation of solution-driven oxides for application in thin film transistors (TFTs). In current study, a fully solution-based method, using 2-methoxyethanol as solvent, has been adopted to prepare InZnO thin films and HfAlO x gate dielectrics. Amorphous HfAlO x thin films annealed at 600 C have shown a high transparency (>85%), low leakage current density (6.9 Â 10 À9 A cm À2 at 2 MV cm À1 ), and smooth surface. To verify the potential applications of HfAlO x gate dielectrics in oxide-based TFTs, fully solution-induced InZnO/HfAlO x TFTs have been integrated. Excellent electrical performance for InZnO/HfAlO x TFTs annealed at 450 C has been observed, including a low operating voltage of 3 V, a saturated mobility of 5.17 cm 2 V À1 s À1 , a high I on /I off of $10 6 , a small subthreshold swing of 87 mV per decade, and a threshold voltage shift of 0.52 V under positive bias stress (PBS) for 7200 s, respectively. In addition, time dependent threshold voltage shift under PBS could be described by a stretched-exponential model, which can be due to charge trapping in the semiconductor/dielectric interface. Finally, to explore the possible application in logic operation, a resistor-loaded inverter based on InZnO/HfAlO x TFTs has been built and excellent swing characteristic and well dynamic behavior have been obtained. Therefore, it can be concluded that fully solution-driven InZnO/HfAlO x TFTs have demonstrated potential application in nontoxic, eco-friendly and low-power consumption oxide-based flexible electronics. rsc.li/rsc-advances 36584 | RSC Adv., 2018, 8, 36584-36595 This journal is

Balanced Performance Improvement of a-InGaZnO Thin-Film Transistors Using ALD-Derived Al2O3-Passivated High-k HfGdOx Dielectrics

“…Although the V TH shift of TFT caused by PBS results in the increase of V ST , this kind of voltage shift (also called plasticity) is very favorable to the application of new-concept synaptic devices, and it is convenient to realize the learning rule of the spike-timing-dependent-plasticity (STDP). , Figure b is the function curve of voltage gain versus V DD extracted from VTCs. The voltage gain increases linearly with V DD as shown in Figure e, which is consistent with the literature. , Compared with some previously reported complementary metal–oxide–semiconductor (CMOS) inverters, the inverter in this work obtained a higher voltage gain at lower V DD . , From Figure b, it can also be found that the input voltage (expressed as V GAIN‑MAX ) corresponding to the maximum voltage gain under each V DD increases with the increase of V DD . It can be noted from the comparison that V GAIN‑MAX and V ST are approximately equal at each V DD , as shown in Figure d.…”

“…Generally, the larger the characteristic capture time (τ) is, the greater the defect trap density is. In the current work, the τ value obtained by fitting is 823.78, which is smaller than the results reported in the literature. − This result verifies the previous determination that the passivation of the HGO film surface by Al 2 O 3 is beneficial to improve the interface quality.…”

“…The voltage gain increases linearly with V DD as shown in Figure 9e, which is consistent with the literature. 15,54 Compared with some previously reported complementary metal−oxide−semiconductor (CMOS) inverters, the inverter in this work obtained a higher voltage gain at lower V DD . 62,63 From Figure 9b, it can also be found that the input voltage (expressed as V GAIN-MAX ) corresponding to the maximum voltage gain under each V DD increases with the increase of V DD .…”

“…53 In the current work, the result of nonlinear fitting for the function relation of ΔV TH vs stress time (t) shows that the captured charge can be redistributed in the Al 2 O 3 dielectric, which is consistent with the previous research literature. 53 The time dependence of ΔV TH reflected by the stretchedexponential model can be described as follows 15,54…”

“…The time dependence of Δ V TH reflected by the stretched-exponential model can be described as follows , where t is the stress time, Δ V TH∞ denotes Δ V TH when t tends to infinity, τ represents the characteristic trapping time of charge, and β is on behalf of the stretched-exponential exponent. Generally, the larger the characteristic capture time (τ) is, the greater the defect trap density is.…”