Lanthanum Doping in Zinc Oxide for Highly Reliable Thin-Film Transistors on Flexible Substrates by Spray Pyrolysis

Abstract

Solution-processed metal-oxide thin-film transistors (TFTs) are considered as one of the most favorable devices for next-generation, large-area flexible electronics. In this paper, we demonstrate the excellent material properties of lanthanum−zinc oxide (LaZnO) thin films deposited by spray pyrolysis and their application to TFTs. The threshold voltage of the LaZnO TFTs shifts toward positive gate voltage, and the mobility decreases with increasing lanthanum ratio in ZnO from 0 to 20%. The purification of the LaZnO precursor (P-LaZnO) further improves the device performance. The P-LaZnO TFT exhibits a field-effect mobility of 22.43 cm 2 V −1 s −1 , zero hysteresis voltage, and negligible threshold voltage V TH shift under positive bias temperature stress. The enhancement in the electrical properties is due to a decrease in grain size, smooth surface roughness, and reduction in the trap density in the LaZnO film. X-ray photoelectron spectroscopy (XPS) results confirm the presence of La in the TFT channel and at/near the interface of the LaZnO and ZrO x gate insulator, leading to fewer interfacial traps. The flexible P-LaZnO TFT fabricated on the polyimide substrate exhibits a mobility of 17.64 cm 2 V −1 s −1 and a negligible V TH shift under bias stress. Also, the inverter made of LZO TFTs is working well with a voltage gain of 17.74 (V/V) at 4 V. Therefore, the LaZnO TFT is a promising device for next-generation flexible displays.

Extremely Stable, High Performance Gd and Li Alloyed ZnO Thin Film Transistor by Spray Pyrolysis

“…12.38 10 7 --2019 [23] e) LaInZnO/ b) SiN x 150 2.64 10 9 --2010 [44] a) LaInZnO/ b) SiN x 550 4.2 10 6 1 -2012 [45] a) HfInZnO/ b) SiN x 500 1.94 10 6 --2010 [26] a) ZrInZnO/ a) LaZrO 400 6.23 10 9 -3.5 2013 [27] a) LaZnSnO/ b SiO 2 500 4.2 10 8 --2016 [28] a) LaZnO/ b) ZrO x 350 22.43 10 8 ≈0 0.06 2020 [63] d) ZrZnO/ d) AlO x 150 12.38 10 7 -0.61 2019 [64] a) (ZnO/InO 3 )/ b) SiO 2 200 50 10 5 -3.4 2019 [65] a) ZnO/ b) SiO 2 150 4.5 10 6 22 2018 [66] e) YZnO/ b) SiO 2 150 9.8 10 7 -5.3 2019 [67] d) (ZnO/4MP)/ d) Al 2 O 3 150 30 10 5 -2.3 2020 [68] a)…”

“…Therefore, MO, V o , and −OH are deconvoluted separately. [ 1,14,31,39,63 ] According to the binding energy level these subpeaks assigned to metal oxygen (O I ), oxygen vacancy (O II ), and hydroxyl group (O III ). MO, V o , and OH percentage were calculated as O I /(O I + O II + O III ) × 100, O II /(O I + O II + O III )×100, O III /(O I + O II + O III )×100.…”

“…Therefore, MO, V o , and −OH are deconvoluted separately. [1,14,31,39,63] According to the binding energy level these subpeaks assigned to metal oxygen ( )×100. We observed the increase of metal-oxygen bond and decrease of V o from MO bonding peak to V o peak ratio.…”

“…The device performances such as mobility, on/off current ratio, and SS of previous reports with our results are summarized in Table 1. [1,23,24,[26][27][28]41,[44][45]52,[54][55][56][57][63][64][65][66][67][68] To explain the role of Gd and Li in ZnO, we propose a model shown in Figure 5d-f, where the Zn 2+ ion can be replaced by the Gd 3+ ion, reducing electron concentration in a channel. The Li + replaces the Zn 2+ interstitial site, inducing extra electron in the channel.…”

Reduction of Hysteresis in Hybrid Perovskite Transistors by Solvent-Controlled Growth

“…The total trap density (N T ) can be calculated from N T = {SS(log(e))/(k B T/q) − 1}(C ox /q) where k B , T, and q are respectively the elementary electric charge, Boltzmann’s constant, and temperature in kelvins [ 51 ]. N T values of the TFTs with and without SCG were approximately 1.29 × 10 12 and 1.06 × 10 13 cm − 2 ·V −1 , respectively [ 51 , 52 ]. The difference in N T was mainly due to the bulk states, given that the TFTs employ the same gate insulator.…”