Optically detected magnetic resonance of indirect excitons in an ensemble of (In,Al,Ga)As/(Al,Ga)As quantum dots

Quantum Dots as an Active Reservoir for Longer Effective Lifetimes in GaAs Bulk

“…The higher values for a 1 and a 3 indicate a wider size distribution of these specimens of QDs and a larger FWHM for peaks 1 and 3 in comparison with peak 2. 21 As expected, the PL designated to the indirect transitions exhibit a larger broadening than the direct ones. 34,35 Figure 2d displays the corresponding intensity modulation for the QD and defect-related emissions with a highlight within the carrier redistribution region at low excitation powers (5 × 10 −3 − 1.5 × 10 −1 W/cm 2 ).…”

“…One prominent feature arising from AlInAs/AlGaAs systems is the possibility of tuning different band alignments in the electronic band structure depending on dot composition and size, that subsequently impacts their optical response. Several works have reported the coexistence of direct type-I and indirect type-II transitions, − and also indirect type-I emissions in similar compositions. , Each one of those will grant different advantages for specific applications, i.e., direct type-I emissions generally show stronger recombination efficiency due to the larger overlap between the electron and hole wave functions; direct type-II ones offer longer lifetimes, which may be useful for more efficient collection of carriers and memory purposes, and finally, indirect transitions provide weak exchange interaction, resulting in weaker spin decoherence mechanisms . Therefore, an accurate assessment of the optical emission character becomes paramount for exploring new applications and technologies using these QD structures.…”

“…6,19 Each one of those will grant different advantages for specific applications, i.e., direct type-I emissions generally show stronger recombination efficiency due to the larger overlap between the electron and hole wave functions; direct type-II ones offer longer lifetimes, which may be useful for more efficient collection of carriers and memory purposes, 20 and finally, indirect transitions provide weak exchange interaction, resulting in weaker spin decoherence mechanisms. 21 Therefore, an accurate assessment of the optical emission character becomes paramount for exploring new applications and technologies using these QD structures. Such nanostructures have also been exploited for hot-carrier photovoltaic devices, where the excess kinetic energy of carriers may be useful for enhancing the efficiency of traditional solar cells by extracting them before their picosecond-scale thermalization or by producing more electron−hole pairs by multiple exciton generation mechanisms.…”

Optical Orientation of Excitons in a Longitudinal Magnetic Field in Indirect-Band-Gap (In,Al)As/AlAs Quantum Dots with Type-I Band Alignment

“…We can estimate the anisotropic exchange interaction for indirect excitons as [ 12 ], where is the Bohr magneton and is the electron g -factor. With (which was measured using spin-flip Raman scattering [ 42 ] and optically detected magnetic resonance [ 43 , 44 ]), we obtain μeV, which is indeed several orders of magnitude smaller than the of several hundreds of microelectronvolts observed in direct-band-gap (In,Al)As/AlAs QDs [ 8 ].…”

Theoretical model for the description of a single quantum dot using geometry

“…They are represented by geometrical structures, where the states of the system are described by points, the observables are real-valued functions, and the quantum evolution is governed by a Hamiltonian operator [1][2][3][4][5]. Semiconductor structures such as InAs and GaAs (among other semiconductors) have been studied extensively in recent years and continue to be objects of study because of their important physical properties and their great potential for applications in technology [6][7][8][9][10][11][12][13][14][15][16][17][18][19][20][21][22][23]. It is well known that geometry is present in physics at all scales of measures.…”