Miniband formation in a quantum dot crystal

Abstract

We analyze the carrier energy band structure in a three-dimensional regimented array of semiconductor quantum dots using an envelope function approximation. The coupling among quantum dots leads to a splitting of the quantized carrier energy levels of single dots and formation of three-dimensional minibands. By changing the size of quantum dots, interdot distances, barrier height, and regimentation, one can control the electronic band structure of this artificial quantum dot crystal. Results of simulations carried out for simple cubic and tetragonal quantum dot crystal show that the carrier density of states, effective mass tensor and other properties are different from those of bulk and quantum well superlattices. It has also been established that the properties of artificial crystal are more sensitive to the dot regimentation rather then to the dot shape. The proposed engineering of three-dimensional mini bands in quantum dot crystals allows one to fine-tune electronic and optical properties of such nanostructures.

Transport in random quantum dot superlattices

“…The coupling between QDs splits the energy levels and results in the formation of minibands. 6 From Fig. 3 we observe the occurrence of two well-defined minibands below the barrier when disorder is absent, in agreement with previous results.…”

“…3 we observe the occurrence of two well-defined minibands below the barrier when disorder is absent, in agreement with previous results. 6 Each band is characterized by four main conductance peaks and each peak is the convolution of four closer peaks that cannot be resolved except in the low energy region of the higher miniband ͑see inset of Fig. 3͒.…”

“…The occurrence of minibands has been established. 6 However, the lack of periodicity in random QDs superlattices requires different approaches.…”

Absorption coefficient for the intraband transitions in quantum dot materials

“…(A3) and the a's obtained by application of Eq. (10). In this table, the spin degeneracy is not taken into account in calculating a wn , and the polarization factor is taken to be 1.…”

“…Transitions to other BSs are Dirac-delta shaped, following Eq. (10). Given that, for a = b>c, the first excited states are the degenerate (2,1,1) and (1,2,1) states; the absorption coefficient for transitions from the fundamental or first excited state to all other BSs is where £ Une is, in each instance, the energy difference between the final and initial state in question.…”