Shape and Interband Transition Behavior of InAs Quantum Dots Dependent on Number of Stacking Cycles

Abstract

InAs/GaAs multistacked quantum dot (QD) layers were grown by using molecular beam epitaxy with various numbers of stacking cycles to investigate the shape and the interband transition in the InAs QDs. The appearance of another photoluminescence (PL) peak on InAs/GaAs QDs with more than six stacking cycles originated from the change of the QDs from an isotropic pyramidal shape to an elongated anisotropic pyramidal shape. Dislocation lines along the [1 1 10] direction existing on the InAs/GaAs QDs with more than six stacking cycles were attributed to the existence of excessive strain fields. Scanning transmission electron microscope and atomic force microscope images showed that the QD shape in the [1 1 10] direction was elongated without any remarkable change in the volume of the QDs. These results indicate that the shape of the InAs/GaAs QDs was strongly affected by the number of the stacking cycles and that the appearance of another PL peak is related to the change of the QD shape.

Realization of high-luminous-efficiency InGaN light-emitting diodes in the “green gap” range

“…The existence of the QDs is responsible for the high radiative efficiency despite the high dislocation density in InGaN. In the conventional green LED sample, each QW contains a high-indium-concentration InGaN layer, so a large accumulated stress is expected with the increased stacking of QW layers, and this increased stress causes degradation of the crystal quality in the top QW layer, as also occurs in InAs multilayer QDs 27 . The QDs are inevitably impaired, resulting in the quenching and broadening of the emission peak.…”

Growth of Columnar Quantum Dots by Metalorganic Vapor-Phase Epitaxy for Semiconductor Optical Amplifiers

“…The formation of dislocations is considered to be due to the accumulation of compressive strain of InAs, as observed in multistacked QD layers with thin barrier layers. 12) When the thickness of the 3.7%-strained barrier layers was increased to 4 ML, stacking faults were generated as shown in Fig. 1(c).…”

Atomic-Scale Characterization of Droplet Epitaxy Quantum Dots

“…The critical thickness or critical strain is a function of composition of the epitaxial layer. The strain relaxation can also lead to the formation of crystal defects, which strongly affect the optoelectronic properties of the QDs [ 30 , 31 , 32 , 33 ]. Developments in the growth techniques such as MBE or MOVPE in combination with decades of growth optimization made it possible to realize (nearly) defect free QDs.…”