In-plane optical polarization and dynamic properties of the near-band-edge emission of an m-plane freestanding AlN substrate and a homoepitaxial film
At a Glance
Section titled āAt a Glanceā| Metadata | Details |
|---|---|
| Publication Date | 2019-10-07 |
| Journal | Applied Physics Letters |
| Authors | Shigefusa F. Chichibu, Kazunobu Kojima, K. Hazu, Y. Ishikawa, K. Furusawa |
| Institutions | North Carolina State University, Tohoku University |
| Citations | 17 |
Abstract
Section titled āAbstractāFor accelerating the development of deep-ultraviolet light-emitting diodes based on high AlN mole fraction (x) AlxGa1-xN for sterilization, disinfection, and skin therapy applications, in-plane optical polarization and dynamic properties of the near-band edge (NBE) cathodoluminescence (CL) peak of a low threading dislocation density (<103 cmā2) m-plane freestanding AlN substrate and a homoepitaxial film are assessed. Consistent with the polarization selection rules, the electric field (E) component of the NBE emission was essentially polarized parallel to the c-axis (Eā„c). Low-temperature CL spectra of the homoepitaxial film exhibited exciton fine structures: CL peaks at 6.0410 and 6.0279 eV, which were polarized Eā„c and E perpendicular to the c-axis (Eā„c), respectively, are assigned as being due to the recombination of free A-excitons of irreducible representations Ī1 and Ī5. The hydrogenic binding energy of the Ī1 A-exciton being 51 meV is verified. Detectable CL peaks under Eā„c polarization at 6.0315 and 6.0212 eV are tentatively assigned as Ī1-mixed Ī5-exciton-polaritons. The concentration of multiple vacancies consisting of an Al-vacancy (VAl) and N-vacancies (VNs), namely, VAlVN2ā3, in the substrate was estimated by the positron annihilation measurement to be 2-3 Ć 1016 cmā3, while that in the epilayer was lower than the detection limit (<1016 cmā3). The NBE CL lifetime of 28 ps of the epilayer subsurface at 300 K is likely limited by the recombination at carbon deep-acceptors on nitrogen sites (3 Ć 1017 cmā3) and/or VAlVN2ā3 Shockley-Read-Hall nonradiative recombination centers (ā¼1 Ć 1016 cmā3) with hole capture coefficients of approximately 1Ć10ā7 and 3Ć10ā6 cm3 sā1, respectively.