Metal-insulator transition at a depleted LaAlO3/SrTiO3 interface: Evidence for charge transfer induced by SrTiO3 phase transitions

Two anomalous bias dependent resistive peaks induced by the SrTiO3 structural phase transitions at 55 and 110 K were observed in a LaAlO3/SrTiO3 and Nb:SrTiO3 rectifying junction when the LaAlO3/SrTiO3 was depleted under reverse bias. At these transition temperatures, the barrier between LaAlO3/SrTiO3 and Nb:SrTiO3 showed abrupt changes in the tunneling energy under forward bias. The peak at 110 K was an insulator-metal phase transition while the peak at 55 K was a metal-insulator one. We propose that the phase transitions of the SrTiO3 substrate influence the charge transfer to the LaAlO3/SrTiO3 layer, giving rise to these anomalous resistive peaks.