Stranski–Krastanov InAs/GaAsSb quantum dots coupled with sub-monolayer quantum dot stacks as a promising absorber for intermediate band solar cells

Abstract

The optical properties of the Stranski–Krastanov (S–K) grown InAs/GaAsSb quantum dots (QDs) coupled to sub-monolayer (SML) InAs QD stacks are investigated using photoluminescence (PL) spectroscopy. The PL emission peak of the S–K QDs shifts to shorter wavelengths with increasing the number of SML stacks (NSML) due to the increasing strain fields from the SML QDs. The PL peak energy is linearly increased with increasing the cube root of excitation power, with a different ratio of the absorption coefficient to radiative recombination rate for all the QD samples. The total carrier lifetime for the S–K QDs is increased with increasing NSML, most probably caused by the increase in the ground-state transition energy of the S–K QDs. The nonmonotonic behavior of the thermal activation energy of electrons in the S–K QDs is observed due to the NSML-dependent variation of the strain and Coulombic interaction within the QDs.

Correlation between the structure and luminescence of InAs submonolayer stacked nanostructures

“…In particular, the SMLS growth mode is a proposed alternative to the better-established Stranski-Krastanov (SK) growth mode in assembling the InAs nanostructures for applications including lasers, [1][2][3][4][5][6][7][8][9][10][11][12][13] photodetectors, [14][15][16][17][18][19][20] and photovoltaics. [21][22][23][24] Compared to the single (one-shot) InAs deposition involved in SK growth, SMLS growth involves the cycled, alternating deposition of SML-thick InAs and ML-thick GaAs which form stacked 1-ML-high 2D islands of InAs embedded in a GaAs matrix. Compared to the SK growth mode, where a thin contiguous InAs wetting layer (WL) is known to form prior to quantum dot (QD) formation, such a contiguous layer does not likely form in SMLS growth, owing to the SML coverage of the InAs layers.…”

“…Compared to the SK growth mode, where a thin contiguous InAs wetting layer (WL) is known to form prior to quantum dot (QD) formation, such a contiguous layer does not likely form in SMLS growth, owing to the SML coverage of the InAs layers. 6,14,16,21,[25][26][27][28] In addition, a distinct advantage of SMLS is the flexibility and tunability of the growth. By adjusting the deposited amount of InAs and GaAs in each cycle, as well as the total number of cycles, the size, shape, and height of the InAs nanostructures, and hence their optical properties, can be controlled.…”

Effect of Sb composition on the band alignment of InAs/GaAsSb quantum dots*

“…As zero-dimension active gain materials, quantum dots (QDs) have been widely used in opto-electronic devices, such as communication lasers, [1,2] silicon photonics transmitters, [3] infrared detectors, [4,5] Q-bit emitters, [6] and intermediateband solar cells (IBSC). [7,8] To enhance the performance of IBSCs and infrared detectors, QDs with long carrier lifetime are highly desirable. [9] During last decade, InAs/GaAsSb QDs have attracted much interest because of its variable band alignment.…”