Abstract: A sparse-carrier device includes a crystal structure with a crystallographic facet having contacts at opposite ends. Quantum dots are formed in first and second rows on the facet approximately one quantum dot wide and a plurality of quantum dots long, the quantum dots in the first row being separated from each other by a first distance smaller than a second distance between the quantum dots in the first row and adjacent quantum dots in a second row. The first distance is small enough to allow carrier tunneling between adjacent quantum dots and the second distance is large enough to substantially prevent tunneling between adjacent quantum dots and small enough to allow Coulombic interaction between adjacent quantum dots. Electrical contacts are formed at opposite ends of the rows to allow tunneling of carriers into and out of quantum dots in the first and second rows.