title: Terahertz ionization of highly charged quantum posts in a perforated electron gas.
abstract: "Quantum posts" are roughly cylindrical semiconductor nanostructures that are embedded in an energetically shallower "matrix" quantum well of comparable thickness. We report measurements of voltage-controlled charging and terahertz absorption of 30 nm thick InGaAs quantum wells and posts. Under flat-band (zero-electric field) conditions, the quantum posts each contain approximately six electrons, and an additional ~2.4 × 10(11) cm(-2) electrons populate the quantum well matrix. In this regime, absorption spectra show peaks at 3.5 and 4.8 THz (14 and 19 meV) whose relative amplitude depends strongly on temperature. These peaks are assigned to intersubband transitions of electrons in the quantum well matrix. A third, broader feature has a temperature-independent amplitude and is assigned to an absorption involving quantum posts. Eight-band k·p calculations incorporating the effects of strain and Coulomb repulsion predict that the electrons in the posts strongly repel the electrons in the quantum well matrix, "perforating" the electron gas. The strongest calculated transition, which has a frequency close to the center of the quantum post related absorption at 5 THz (20 meV), is an ionizing transition from a filled state to a quasi-bound state that can easily scatter to empty states in the quantum well matrix.
authors.affiliation: Department of Physics, University of California, Santa Barbara, Santa Barbara, California 93106, USA. cmorris@physics.ucsb.edu
authors.forename: Christopher M
authors.initials: CM
authors.lastname: Morris
authors.forename: Dominik
authors.initials: D
authors.lastname: Stehr
authors.forename: Hyochul
authors.initials: H
authors.lastname: Kim
authors.forename: Tuan-Anh
authors.initials: TA
authors.lastname: Truong
authors.forename: Craig
authors.initials: C
authors.lastname: Pryor
authors.forename: Pierre M
authors.initials: PM
authors.lastname: Petroff
authors.forename: Mark S
authors.initials: MS
authors.lastname: Sherwin
mesh_terms: D000042:Absorption; D001152:Arsenicals / Q000737:chemistry*; D003198:Computer Simulation; D004583:Electrons; D005740:Gases / Q000737:chemistry*; D007204:Indium / Q000737:chemistry*; D008956:Models, Chemical; D045663:Quantum Dots; D012666:Semiconductors; D055672:Static Electricity; D055053:Terahertz Radiation
chemical_list: D001152:Arsenicals; D005740:Gases; D007204:Indium; C076773:indium arsenide