Al incorporation during metal organic chemical vapour deposition of aluminium zinc oxide

THIN SOLID FILMS

卷:709

Article

Ellingsen, Josef¹  Venkatachalapathy, Vishnukanthan^1,3  Azarov, Alexander¹  Nilsen, Ola²  Kuznetsov, Andrej¹ 

[1] Univ Oslo, Dept Phys, LENS, POB 1048, N-0316 Oslo, Norway

[2] Univ Oslo, Dept Chem, NAFUMA, POB 1033, N-0315 Oslo, Norway

[3] Natl Res Nucl Univ MEPhI, Dept Mat Sci, 31 Kashirskoe Sh, Moscow, Russia

关键词: Thin films;    Metal-organic chemical vapor deposition;    Growth conditions;    Boundary layer;    Doping;    Compound semiconductors;    Aluminum-doped zinc oxide (TSF scientific staff);   

DOI  :  10.1016/j.tsf.2020.138245

来源: Elsevier

【 摘 要 】

Aluminium zinc oxide (AZO) is a promising transparent conductive oxide this is difficult to fabricate by metal-organic chemical vapour deposition (MOCVD) because of prereactions between the precursors for Al and oxygen. One way of reducing prereactions is to use separate injectors. In this work, we investigated the effect of separate injectors and various flow configurations on the MOCVD fabrication of AZO using diethyl zinc (DEZn), tert-butanol (tBuOH), and trimethyl aluminium (TMAl) precursors. X-ray diffraction revealed that the resulting films maintained a purely wurtzite ZnO structure, and that the Al incorporation changed the c lattice parameters from 5.207 to 5.181 angstrom in agreement with theoretical models of mixing on the Zn sub-lattice. This indicates that Al was mainly incorporated onto the Zn sub-lattice. The maximum Al concentration was 6 x 10(21) cm(-3). The Al concentration was directly influenced by the TMAl flow rates, but the incorporation efficiency of Al also depended on the O/Zn balance as determined by the tBuOH supply and the total flow rate through the TMAl+DEZn injector. The tBuOH supply decreased the incorporation efficiency, while it increased for higher total flow in the TMAl+DEZn injector although both changes nominally increases the O/Zn balance. This dual, but contradicting, dependency on the O/Zn suggested that the incorporation efficiency depended not only on precursor supply, but also on the chemical stability of the Al species present at the growth interface. The concept of a reaction depth of TMAl was introduced to discuss the observed trends, and a qualitative model was suggested to explain how the Al-species present at the growth interface are determined by the relative depths of the reaction depth and the boundary layer. These findings illustrate the limits of the O/Zn parameter when using separate injectors because the properties of the boundary layer can affect Al incorporation during MOCVD growth. This should be relevant for MOCVD growth of other compound semiconductor systems that are grown using separate injectors.

【 授权许可】

Free