Epitaxial growth of high mobility Cu2O thin films and application to p-channel thin film transistor

Abstract

Cu 2 O epitaxial films were grown for high mobility p-channel oxide thin-film transistors (TFTs). The use of a (110) MgO surface and fine tuning of a growth condition produced single phase epitaxial films with hole Hall mobilities ∼90 cm2 V−1 s−1 comparable to those of single crystals (∼100 cm2 V−1 s−1). TFTs using the epitaxial film channels exhibited p-channel operation although the field-effect mobilities and the on-to-off current ratio were not yet satisfactory (∼0.26 cm2 V−1 s−1 and ∼6, respectively).

Growth of ∼5 cm2V−1s−1 mobility, p-type Copper(I) oxide (Cu2O) films by fast atmospheric atomic layer deposition (AALD) at 225°C and below

“…[http://dx.doi.org/10.1063/1.4771681] Cu 2 O is attracting great interest in a wide variety of applications, including as anode in batteries, 1 gas sensors, 2 catalysis, 3 biosensing applications, 4 resistive RAM, 5 photovoltaics, 6 photoelectrochemical water splitting, 7 p-type thin film transistors (TFT) [8][9][10] and CMOS; 11 as well as in other all-oxide transparent electronic applications. 12 When used as a p-type material, the simple binary composition of Cu 2 O gives it a processing advantage over the more complicated ternary oxides (e.g.…”

“…For Cu 2 O in inorganic solar cells, high carrier concentrations of at least 10 16 cm −3 are necessary to achieve the full depletion layer width, thus allowing high open circuit voltage and near theoretical J sc values to be obtained. 13 Cu 2 O thin films can be deposited by several methods including pulsed laser deposition (PLD), 8 sputtering, 14 thermal oxidation, 15 spray pyrolysis 16 and electrochemical deposition. 17 Sputtering appears to be the most successful vacuum method for achieving high mobilities at low temperatures.…”

p-channel thin-film transistors based on spray-coated Cu2O films

“…In order to prepare Cu 2 O thin film, the most straightforward way is the controlled oxidation of a precursor Cu layer 21,22 or using more advanced variations such as radical oxidation by O 2 plasma, 23 all of which are simple methods that could produce good quality Cu 2 O films. However, for device fabrication, the need to obtain high fieldeffect mobility along with the multiple-phase nature of Cu-O material system (Cu, Cu 2 O, and CuO) have led to the focus on complex vacuum-based deposition techniques such as pulsedlaser deposition (PLD) 14,24 and sputtering 25,26 with the aim to produce single-phase, high-quality Cu 2 O films for transistor applications. These methods, however, rely on stringent experimental conditions and are incompatible with high-throughput manufacturing processes, especially when compared to solution-based deposition techniques.…”

Single phase, single orientation Cu2O (1 0 0) and (1 1 0) thin films grown by plasma-assisted molecular beam epitaxy

“…MBE synthesis of Cu 2 O on MgO substrates has been demonstrated using pure atomic oxygen [7,8,9], however no reports of a diluted oxygen plasma have been made to date. Also, growth on MgO (1 1 0) surface has been reported by sputtering [10] and pulsed laser deposition [11], but not by MBE. DFT calculations [12] show that the Cu 2 O (1 1 0) surface has the lowest energy, so it is reasonable to assume that a substrate that promotes growth in this direction may foster Cu 2 O phase stability over a larger range of deposition parameters, and this is consistent with results of this work.…”