Room-temperature luminescence of excitons in ZnO/(Mg, Zn)O multiple quantum wells on lattice-matched substrates

We report on the optical properties of ZnO/(Mg, Zn)O multiple quantum wells (MQWs) on lattice-matched ScAlMgO4 substrates fabricated by laser molecula r-beam epitaxy. As the well layer thickness decreased down to 7 Angstrom, t he photoluminescence (PL) and absorption peaks showed a systematic blueshif t, consistent with the quantum-size effect. Moreover, a bright PL of free e xcitons could be observed even at room temperature. As a result, the PL cou ld be tuned in the energy range of 3.3-3.6 eV by choosing the appropriate b arrier height and well layer thickness. The widest tunability on the room-t emperature luminescence of the excitons could be attained on the basis of t he ZnO quantum structure. These favorable properties could not be attained in the MQWs on lattice-mismatched sapphire substrates. (C) 2000 American In stitute of Physics. [S0003-6951(00)04533-2].