Optical properties of transition metal oxide quantum wells

Abstract

Fabrication of a quantum well, a structure that confines the electron motion along one or more spatial directions, is a powerful method of controlling the electronic structure and corresponding optical response of a material. For example, semiconductor quantum wells are used to enhance optical properties of laser diodes. The ability to control the growth of transition metal oxide films to atomic precision opens an exciting opportunity of engineering quantum wells in these materials. The wide range of transition metal oxide band gaps offers unprecedented control of confinement while the strong correlation of d-electrons allows for various cooperative phenomena to come into play. Here, we combine density functional theory and tight-binding model Hamiltonian analysis to provide a simple physical picture of transition metal oxide quantum well states using a SrO/ SrTiO 3 /SrO heterostructure as an example. The optical properties of the well are investigated by computing the frequency-dependent dielectric functions. The effect of an external electric field, which is essential for electro-optical devices, is also considered. V C 2015 AIP Publishing LLC.

Quantum Confinement in Oxide Heterostructures: Room-Temperature Intersubband Absorption in SrTiO3/LaAlO3 Multiple Quantum Wells

“…TB has been employed previously to compute the electronic band structure and corresponding photon absorption spectrum in bulk TMOs and similar TMO QW heterostructures. 51 Here, we calculate the frequency-dependent dielectric function of STO QWs and plot the imaginary part of the dielectric function, corresponding to absorption in the heterostructures. The calculated spectra agree well with the experimental spectra in several respects.…”

“…Tight-binding: The details of the tight-binding (TB) simulations can be found in our previous work. 51 Following the notations in Lin et al, 51 , and , = 0.3 . The temperature is 300 K, and the chemical potential is chosen to be 4 eV, corresponding to about 1 at% electron doping.…”

“…The details of the TB simulations can be found in our previous work . Following the notations in Lin et al ., the nonzero TB parameters are ϵ t2g = 4.0 eV, t dp,π = 1.5 eV, and t pp,σ = 0.3 eV.…”

Quantum confinement in transition metal oxide quantum wells

“…19 When the STO QW thickness is decreased, the entire conduction band starts feeling the effects of confinement, causing the band structure to develop sub-bands corresponding to the quantum well levels. By controlling the QW thickness, one can manipulate the number of quantized energy levels in the well and their 20 STO films can be readily n-type doped [21][22][23] making STO/LAO QW heterostructures a natural candidate for unipolar ISB devices such as the case for ZnO/ (Mg,Zn)O. 24 Finally, these structures can be readily integrated with conventional semiconductors 25 thus opening a route for hybrid systems involving, e.g., silicon nanophotonics.…”

Oxide‐Based Optoelectronics

“…In Figure 9, we show the intersubband transitions measured by Ortmann et al [61] Experimental results are in excellent agreement with theoretical predictions. [65] Further fabrication advancements, including integration of such epitaxial QWs onto thermally oxidized silicon via direct deposition and the 3D integration of crystalline silicon and epitaxial oxides, promise to bring a variety of oxide-based QW technologies, including infrared photodetectors, quantum cascade lasers, and EO modulators, closer to reality. [66,67]…”