Directed Arrangement of Ge Quantum Dots on Si Mesas by Selective Epitaxial Growth

Abstract

Since the observation of coherent, self-assembled dots in strained heterostructures, such as InAs on GaAs (001) [1] and Ge on Si (001) [2, 3], there has been a considerable interest in exploring their fundamental properties and applications in photonics and electronics. For understanding the nature and the mechanism of the formation of the dots, many studies on the size distribution, evolution, [4] and shape transition [5] of the dots have been carried out. Good size uniformity of self-assembled dots has been reported [6, 7] and self-assembled dot based lasers have been demonstrated [8, 9]. However, controlled spatial arrangement, which is usually required for electronic and signal processing applications, remains a major problem.

Much effort has been focused on controlling spatial distribution, using a variety of techniques, such as growth on miscut substrates with surface steps [10] and on relaxed templates with dislocation networks [11, 12] and stacking growth of multilayers of dots [13,14]. Among them, one of the most effective approaches is using selective epitaxial growth (SEG) mesas as templates for the subsequent Ge growth. This approach shows one-dimensional (1D) ordering of Ge dots along the edges of the Si stripe mesas, formed in patterned windows with large feature sizes prepared by conventional lithography [15].