MgZnO films and ZnO/Mg0.19Zn0.81O single quantum well (QW) structures with well layer thickness from 1 to 4 nm were directly prepared on sapphire substrates at the low substrate temperature of 400 degrees C by pulsed laser deposition (PLD). The photoluminescence (PL) peak of QW shifted from 3.51 to 3.33 eV at room temperature as the well thickness was increased from 2 to 4 nm. The PL peak position of QW with well thickness of 2 nm can be well explained by Varshni's relation and the best fitting to the data were E (0) = 3.558 eV, alpha = 2.17 x 10 (4) eV/K, and beta = 589 K. No S-shape variation of PL peak position with temperature for this QW indicates low-temperature growth is an ideal candidate for eliminating the stain effect in ZnO QW. (C) 2017 Elsevier B.V. All rights reserved.