Transparent conductive Ga‐doped ZnO films fabricated by MOCVD

Abstract

Transparent conductive oxides (TCOs) are used for a variety of different applications, e.g., in solar cells and light emitting diodes (LEDs). Mostly, sputtering is used, which often results in a degradation of the underlying semiconductor material. In this work we report on a “soft” method for the fabrication of ZnO films as TCO layers by using metal organic chemical vapor deposition (MOCVD) at particularly low temperatures. The MOCVD approach has been studied focusing on the TCO key issues: fabrication temperature, morphology, optical, and electrical properties. Very smooth ZnO films with rms values down to 0.8 nm were fabricated at a substrate temperature of only 300 °C. Ga‐doping is well controllable even for high carrier concentrations up to 2 × 1020 cm−3, which is above the Mott‐density leading to metallic‐like behavior of the films. Furthermore all films show excellent optical transparency in the visible spectral range. As a consequence, our MOCVD approach is well suited for the soft fabrication of ZnO‐based TCO layers.

Parametric study of seed‐layer formation for low‐temperature hydrothermal growth of highly oriented ZnO films on glass substrates

“…And with additional heating of the films at 250 °C for 1 h was found to reduce the resistivity for two to three orders of magnitude to as low as few 10 −1 Ω cm. Further improvement of conductivity could be achieved by proper doping or by UV treatment . Recently, Wagata et al succeeded in decreasing the resistivity of the spin‐spray grown ZnO films by three orders of magnitude (to 4.4 × 10 −3 Ω cm) with formation of shallow donors by the photocatalytic decomposition of organic impurities.…”

“…ZnO films are typically deposited onto substrates using various vapor‐based techniques. Most of these techniques have serious drawbacks, such as complicated processing that generally involves costly equipment, expensive single crystal substrates, a need of high temperature and high vacuum conditions, and a relatively low yield . On the other hand, different solution‐based methods of film deposition have been extensively investigated in the recent years.…”

Indium-free GZO thin films prepared using plasma-enhanced atomic layer deposition: toward thin film transistor application

“…Recently, pulsed laser deposition, 26,27 molecular beam epitaxy, 28 metal-organic chemical vapor deposition, [29][30][31] chemical spray, [32][33][34] sol-gel methods, [35][36][37] magnetron sputtering, [38][39][40][41][42] arc plasma evaporation, [43][44][45] ion plating [46][47][48] and other methods have been applied for GZO thin film deposition. Owing to the increasing demand for thinner and smaller electronic products, the attention to atomic layer deposition (ALD) technology has also increased as it can precisely control the thickness and deposit films on highaspect-ratio surfaces.…”

Electrical properties of lightly Ga-doped ZnO nanowires

“…The maximum potential doping concentration in our study based on precursor gas flow rates was limited to ´-4 10 cm 18 3 since higher concentrations no longer resulted in nanowire growth, but rather a porous thin film. There are also reports on effective Ga-doping of ZnO thin films grown with MOCVD with resistivities ~W -10 cm 4 [38][39][40].…”