Metal-insulator transition at a depleted LaAlO₃/SrTiO ₃ interface: Evidence for charge transfer induced by SrTiO ₃ phase transitions

Two anomalous bias dependent resistive peaks induced by the SrTiO ₃ 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.