Quantum\nConfinement in Oxide Heterostructures: Room-Temperature\nIntersubband Absorption in SrTiO₃/LaAlO₃ Multiple\nQuantum Wells

Abstract

The Si-compatibility\nof perovskite heterostructures offers the\nintriguing possibility of producing oxide-based quantum well (QW)\noptoelectronic devices for use in Si photonics. While the SrTiO₃/LaAlO₃ (STO/LAO) system has been studied extensively\nin the hopes of using the interfacial two-dimensional electron gas\nin Si-integrated electronics, the potential to exploit its giant 2.4\neV conduction band offset in oxide-based QW optoelectronic devices\nhas so far been largely ignored. Here, we demonstrate room-temperature\nintersubband absorption in STO/LAO QW heterostructures at energies\non the order of hundreds of meV, including at energies approaching\nthe critically important telecom wavelength of 1.55 μm. We demonstrate\nthe ability to control the absorption energy by changing the width\nof the STO well layers by a single unit cell and present theory showing\ngood agreement with experiment. A detailed structural and chemical\nanalysis of the samples <i>via</i> scanning transmission\nelectron microscopy and electron energy loss spectroscopy is presented.\nThis work represents an important proof-of-concept for the use of\ntransition metal oxide QWs in Si-compatible optoelectronic devices.