Influence Of Charge Compensation Mechanisms On The Sheet Electron Density At Conducting Laalo3/Srtio3-Interfaces

The equilibrium conductance of LaAlO3/SrTiO3 (LAO/STO)-heterointerfaces was investigated at high temperatures (950 K-1100 K) as a function of ambient oxygen partial pressure (pO(2)). Metallic LAO/STO-interfaces were obtained for LAO grown on STO single crystals as well as on STO-buffered (La,Sr)(Al,Ta)O-3 substrates. For both structures, the high temperature sheet carrier density n(S) of the LAO/STO-interface saturates at a value of about 1 x 10(14) cm(-2) for reducing conditions, which indicates the presence of interfacial donor states. A significant decrease of nS is observed at high oxygen partial pressures. According to the defect chemistry model of donor-doped STO, this behavior for oxidizing conditions can be attributed to the formation of Sr-vacancies as charge compensating defects. (C) 2012 American Institute of Physics. [doi:10.1063/1.3679139]