SCANNING ELECTRON MICROSCOPY OBSERVATION OF IN-DEVICE InAs/AlAs QUANTUM DOTS BY SELECTIVE ETCHING OF CAPPING LAYERS

Abstract

Self-assembled InAs/AlAs quantum dots embedded in a resonant tunneling diode device structure are grown by molecular beam epitaxy. Through the selective etching in a C 6 H 8 O 7 · H 2 O-K 3 C 6 H 5 O 7 · H 2 O-H 2 O 2 buffer solution, 310 nm GaAs capping layers are removed and the InAs/AlAs quantum dots are observed by field-emission scanning electron microscopy. It is shown that as-fabricated quantum dots have a diameter of several tens of nanometers and a density of 1010 cm-2 order. The images taken by this means are comparable or slightly better than those of transmission electron microscopy. The undercut of the InAs/AlAs layer near the edges of mesas is detected and that verifies the reliability of the quantum dot images. The inhomogeneous oxidation of the upper AlAs barrier in H 2 O 2 is also observed. By comparing the morphologies of the mesa edge adjacent regions and the rest areas of the sample, it is concluded that the physicochemical reaction introduced in this letter is diffusion limited.