ZnO thin-film transistors with polycrystalline (Ba,Sr)TiO3 gate insulators

Abstract

The electrical characteristics of ZnO thin-film transistors with high-k ͑Ba, Sr͒TiO 3 gate dielectrics are presented. The ZnO and ͑Ba, Sr͒TiO 3 thin films were deposited on Pt, exhibiting polycrystalline characteristics. The thin-film devices demonstrated transistor behavior over the range of 0-10 V with a stable threshold voltage of approximately 1.2 V. The field effect mobility, subthreshold slope, and on/off ratio were measured to be 2.3 cm 2 V −1 s −1 , 0.25 V / decade, and 1.5ϫ 10 8 , respectively. The measured transistor performance characteristics suggest that ZnO / ͑Ba, Sr͒TiO 3 structures are well suited for both polycrystalline thin-film transistors for display applications and future higher performance transistors based on single crystal ZnO.

Low temperature atomic layer deposited ZnO photo thin film transistors

“…8 There is a significantly vibrant literature on ZnO channel TFTs deposited with different methods such as physical vapor deposition, chemical vapor deposition, chemical solution deposition, molecular beam epitaxy, and atomic layer deposition (ALD). [1][2][3][4][9][10][11][12] The on-to-off current ratios, I on /I off , of these devices range from 10 to 10 8 with reported electron mobility values between 0.031 and 56.43 cm 2 /V-s. 2,[13][14][15][16][17] Among all these techniques, ALD is promising due to the low growth temperature, large area uniformity, precise thickness control, highly conformal deposition, and scalability to roll-to-roll processes. Low temperature processing is very crucial for compatibility with flexible substrates.…”

Highly stable thin film transistors using multilayer channel structure

“…1 The tunable conductivity of ZnO thin film makes it a very promising candidate for both passive and active electronic applications. [2][3][4] Although zinc oxide TFTs with good field-effect mobility have been reported using various deposition techniques, [5][6][7][8][9][10] the stability of ZnO and other oxide-based TFTs under gatebias stress is a major concern for display applications. [11][12][13][14] Further, the increased temperature of display devices due to prolonged use or operation under harsh conditions can significantly shift the threshold voltage of the pixel-TFTs, 14,15 which would affect the performance of the corresponding device.…”

Selection of Gate Dielectrics for ZnO Based Thin-Film Transistors

“…La 2 O 3 has a very high subthreshold slope of 1.2 V/decade and hence the electrical performance will be poorer in comparison to others. Figure 5 shows the relationship between threshold voltage and dielectric constant based on the data obtained in [5][6][7][8][9][10][11]. The values are highly scattered as threshold voltage depends on some other factors also.…”

“…Hence we found that HfO 2 , Y 2 O 3 , La 2 O 3 and ZrO 2 are the possible candidates that satisfy the constraints of high dielectric constant and a considerable band gap and conduction band offset. Figure 4 shows the relationship between subthreshold slope and and dielectric constant based on the data obtained in [5][6][7][8][9][10][11]. It can be observed that all the materials except La 2 O 3 have subthreshold slope lying in the range of .18-.23 V/decade.…”