Effect of thin GaAs tensile-strained layer on InAs quantum dots on InP (001) substrate grown by LP-MOVPE

The InAs quantum dots on thin tensile-strained GaAs layer on InP (001) subs trate are grown by LP-MOVPE. Approximately 2 nm GaAs tensile-strained layer is first grown on InP substrate, then 2 monolayer (ML) InAs for sample A, 4 ML for sample B, 6 ML for sample C and 8 ML for sample D are deposited. A n atomic force microscope (AFM) is used to study the behavior of the InAs q uantum dots. For sample A, two types of InAs islands are observed. Strain-i nduced grooves appear on the surface. For the other three samples, the InAs islands arrange along two orthogonal directions and the island density dec reases with an increase in the amount of InAs material. The density of samp le B is as high as 1.9 x 10(10) cm(-2), the densities are 1.39 x 10(10) and 0.79 x 10(10) cm(-2) for samples C and D, respectively. Furthermore, the b ase shape changes for different samples. For samples A and B, the base shap es are round; for sample C, the base changes into ellipsis; but for sample D, the base changes into triangle. The base area increases with an increase in the deposition of InAs. We also investigate the PL spectrum of InAs QDs with GaAs and with it and find that the QDs quality is higher with GaAs la yer. (C) 2000 Published by Elsevier Science B.V. All rights reserved.