Electronic coupling and structural ordering of quantum dots using InAs quantum dot columns

In this article, recent investigations of vertically aligned quantum dot co lumns conducted at Stanford University are reviewed. The quantum dots are I nAs in a matrix of GaAs. Both the quantum dots and quantum dot columns are formed through strain-induced islanding, without lithography. Two aspects o f these columns are discussed. First, the electronic coupling of quantum do ts within columns of up to ten quantum dots is demonstrated. The coupling i s adjusted and improvements to a simple light-emitting diode are shown. Sec ond, increased uniformity of a surface quantum dot layer is shown when a su bsurface layer of these columns are used. The most impressive results occur when the columns contain a large number of islands. Reduced variations in average ensemble height and diameter, called size uniformity, and average n earest neighbor distances, called structural uniformity, are shown. A surfa ce unit cell of islands is demonstrated and the lack of a surface lattice i s discussed.