Causes of the Difference Between Hall Mobility and Field-Effect Mobility for p-Type RF Sputtered Cu₂O Thin-Film Transistors

The high Hall hole mobility ( \mu _{Hall} ) of cuprous oxide (Cu 2 O) has caused great interest in using this semiconductor for p-type devices in a future complementary metal-oxide-semiconductor (CMOS) thin-film transistor (TFT) technology. However, in most studies, the field-effect mobility ( \mu _...

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Bibliographic Details
Published in:IEEE transactions on electron devices 2020-12, Vol.67 (12), p.5557-5563
Main Authors: Jo, Jaesung, Lenef, Julia D., Mashooq, Kishwar, Trejo, Orlando, Dasgupta, Neil P., Peterson, Rebecca L.
Format: Article
Language:English
Subjects:
Annealing
CMOS
Contact resistance
Copper
Copper oxide (CuOₒ)
Copper oxides
cuprous oxide (Cu₂O)
Electric contacts
Electron mobility
Film thickness
Hall effect
Handheld computers
Hole mobility
Iron
Material properties
Oxidation
p-type oxide semiconductor
P-type semiconductors
Semiconductor device measurement
Semiconductor devices
Thin film transistors
thin-film transistor (TFT)
Vacuum annealing
Valence
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Summary:The high Hall hole mobility ( \mu _{Hall} ) of cuprous oxide (Cu 2 O) has caused great interest in using this semiconductor for p-type devices in a future complementary metal-oxide-semiconductor (CMOS) thin-film transistor (TFT) technology. However, in most studies, the field-effect mobility ( \mu _{FE} ) achieved was reported to be much lower than \mu _{Hall} . To understand the large gap between \mu _{Hall} and \mu _{FE} , in this work, we correlate RF sputtered p-type copper oxide (CuO x ) material properties with electrical characteristics by varying the film thickness. After vacuum annealing, the different thicknesses cause differences in the oxidation state and phase. Our results show that films with a higher Cu(I) fraction that form in the Cu 2 O phase give better TFT performance than CuO films. Nonetheless, the TFTs still exhibit a much lower \mu _{FE} of 0.005-0.1 cm 2 /V-s than the measured \mu _{Hall} value of 12.1 cm 2 /V-s. We explore the reasons for this mobility gap by conducting contact resistance ( {R}_{C} ) and interface trap ( {D}_{it} ) analysis. We find that the mobility difference can be minimized by reducing the high contact resistance (~33% of the total resistance in the ON-state) and high density of interface traps ( \sim 3\times 10^{13} cm −2 eV −1 ).
ISSN:0018-9383
1557-9646
DOI:10.1109/TED.2020.3033832