Detecting Spatially Localized Exciton in Self-Organized InAs/InGaAs Quantum Dot Superlattices: a Way to Improve the Photovoltaic Efficiency

Abstract

This paper reports on experimental and theoretical investigations of atypical temperature-dependent photoluminescence properties of multi-stacked InAs quantum dots in close proximity to InGaAs strain-relief underlying quantum well. The InAs/InGaAs/GaAs QD heterostructure was grown by solid-source molecular beam epitaxy (SS-MBE) and investigated via photoluminescence (PL), spectroscopic ellipsometry (SE), and picosecond time-resolved photoluminescence. Distinctive double-emission peaks are observed in the PL spectra of the sample. From the excitation power-dependent and temperature-dependent PL measurements, these emission peaks are associated with the ground-state transition from InAs QDs with two different size populations. Luminescence measurements were carried out as function of temperature in the range of 10–300 K by the PL technique. The low temperature PL has shown an abnormal emission which appeared at the low energy side and is attributed to the recombination through the deep levels. The PL peak energy presents an anomalous behavior as a result of the competition process between localized and delocalized carriers. We propose the localized-state ensemble model to explain the usual photoluminescence behaviors. The quantitative study shows that the quantum well continuum states act as a transit channel for the redistribution of thermally activated carriers. We have determined the localization depth and its effect on the application of the investigated heterostructure for photovoltaic cells. The model gives an overview to a possible amelioration of the InAs/InGaAs/GaAs QDs SCs properties based on the theoretical calculations.

Interband Photoconductivity of Metamorphic InAs/InGaAs Quantum Dots in the 1.3–1.55-μm Window

“…From these measurements and their interpretation, some indications for the use of metamorphic QDs for IR detection can be highlighted: (i) when using x > 0.15, advanced designs allowing to control strain-related defects should be used, similar to what was done for the development of metamorphic QDs [ 19 , 20 , 37 ]; (ii) multilayer stacks of QDs (with a minimum of 10 layers) are needed to obtain a QD PC above the dark current [ 27 , 56 ]; and (iii) as a higher confinements of heavy holes is beneficial for the photocurrent obtained when exciting QDs, advanced designs with higher-gap barriers for heavy holes could be considered [ 51 , 57 ]. Hence, these findings can be very useful for the design of metamorphic QDs aiming at IR detection and the development of metamorphic QD photodetectors.…”

Bipolar Effects in Photovoltage of Metamorphic InAs/InGaAs/GaAs Quantum Dot Heterostructures: Characterization and Design Solutions for Light-Sensitive Devices

“…Numerous investigations have been devoted to improve the photoelectric properties of such light-sensitive devices. For example, the photosensitivity range can be extended via the excitation through intermediate bandgap [ 17 , 18 ] or multiple exciton generation [ 19 , 20 ], so that the power conversion efficiencies of QD-based solar cells can exceed in theory the limits of single-bandgap solar cells [ 21 ]. The methods like strain-balancing [ 22 ] and misfit management technique [ 23 ] as well as the thermal annealing [ 24 ] are used to reduce strains in these structures, operating the working range [ 25 ] as well as increasing the photoresponse due to the suppression of strain-related defects [ 26 ] that can act as recombination centers.…”

Development of a 1550-nm InAs/GaAs Quantum Dot Saturable Absorber Mirror with a Short-Period Superlattice Capping Structure Towards Femtosecond Fiber Laser Applications

“…For the multiple phonon scattering process, the combination of 2 LO phonons in sample 3 can fulfill the scattering of an electron from the CLs to QDs while 2 LO phonons plus 1 LO or 2 LA phonons are required for sample 2. It has been demonstrated that electron relaxation rate is severely reduced when more phonon modes are involved in a multiple phonon scattering process [42–45]. Therefore, the electron relaxation rate in sample 3 is larger than that in sample 2, which accounts for the much enhanced PL intensity of the QDs in sample 3.…”