ZnO grown by atomic layer deposition: A material for transparent electronics and organic heterojunctions

Abstract

We report on zinc oxide thin films grown by atomic layer deposition at a low temperature, which is compatible with a low thermal budget required for some novel electronic devices. By selecting appropriate precursors and process parameters, we were able to obtain films with controllable electrical parameters, from heavily n-type to the resistive ones. Optimization of the growth process together with the low temperature deposition led to ZnO thin films, in which no defect-related photoluminescence bands are observed. Such films show anticorrelation between mobility and free-electron concentration, which indicates that low n electron concentration is a result of lower number of defects rather than the self-compensation effect.

Zinc oxide for electronic, photovoltaic and optoelectronic applications

“…The required electron concentration in the range of 10 17 -10 18 cm -3 can be achieved [6]. Importantly, we observed that electron mobility in ZnO films grown by the ALD is relatively weakly dependent on film crystallinity [10,11].…”

“…Use of the ALD and DEZn enabled us reduction of the growth temperature to about 100 °C, which enabled not only construction of Schottky diodes with excellent rectification rates [1,3], but also fully ZnO-based p-n diodes [6]. Moreover, low growth temperature allowed us construction of hybrid structures of the type ZnO/organic material [1,[7][8][9] with very good rectification rate and high current density, as will be discussed further on.…”

“…ZnO is an ideal material for the application in the transparent electronics [6]. The required electron concentration in the range of 10 17 -10 18 cm -3 can be achieved [6].…”

“…Here use of the ALD method is very crucial. Once growth conditions were optimized ZnO films showing only the band edge emission were obtained by us [4][5][6]. By coating of organic material with such ZnO films devices stable in time were constructed [7,38] (see Fig.…”

Research Update: Doping ZnO and TiO2 for solar cells

“…20 But unlike sol-gel deposition, ALD (like MOCVD) is limited because of the need for vacuum-processing, which restricts the size of the substrates, increases the total deposition time, and increases the processing complexity and cost. 18,21,22 Also, organometallic precursors, which are often expensive and pyrophoric, are typically used in MOCVD or ALD.…”