State mixing in InAs/GaAs quantum dots at the pressure-induced Γ-Xcrossing

Abstract

We have measured low-temperature (T = 10 K) photoluminescence spectra of lnAs quantum dots embedded in a GaAs crystalline matrix under hydrostatic pressures up to 7 GPa. Below 4.2 GPa the spectra are dominated by the emission related to the I'-like electronheavy-hole exciton in the InAs dots. Above 4.2 GPa the spectra show two luminescence bands that shift to lower energies with increasing pressure. These bands are attributed to the type-I transition between X "and heavyhole states in the dots and the type-II transition from X states in GaAs to InAs heavy-hole states, respectively. In the I'-X crossover regime we 6nd evidence for a pronounced anticrossing behavior due to mixing between InAs I'-like and GaAs X-like states. The corresponding interaction potential is estimated to be 9 meV, which is an order of magnitude larger compared to mixing interactions reported for semiconductor superlattices.

Three-Dimensional Confinement in the Conduction Band Structure of InP

“…Since the bowing in the emission peak behavior is mainly accounted for by the changes in dE p ͞dp, the intervalley mixing potentials obtained from the fit V GL 2 meV and V LX 10 meV are smaller and comparable to those calculated in Ref. [3], and measured in InAs͞GaAs QDs [12].…”

“…But the band crossing behavior and associated intensity changes of InP QDs may be more complex than just described, depending on the strength of G-L-X intervalley mixing. In the presence of intervalley mixing, the conduction band states near a transition show an anticrossing behavior which is reflected in hydrostatic pressure experiments as a splitting of optical transitions and smearing out of their pressure dependence [12,13]. Depending on the strength of the mixing, the QD peak emission energy shift with pressure could significantly depart from the bulk behavior.…”

“…(2) is obtained from first order perturbation theory when two states, G and X in this case, interact or become mixed near a critical pressure P c [12]. a G and a X in Eq.…”

“…E͑P c ͒ is the energy at which the unperturbed states would cross; i.e., E G ͑P c ͒ E X ͑P c ͒ and V GX is the interaction or mixing potential. In our simulation, a G was elected to be the value of dE p ͞dp measured close to atmospheric pressure, and a X was set equal to 216 meV͞GPa, a typical value for the X pressure coefficient, and equal to that measured in InAs͞GaAs QDs [1,12,14]. Using a G , a X , and considering the X-excitonic band-gap energy to vary with dot size as E dot X 2.3 1 135.8992͞d 1.7165 [15], P c was calculated for each dot size within the ensemble.…”

Baric properties of InAs quantum dots

“…This fact stimulated us to carry out the theoretical calculation of baric coefficients of the energy of the radiative transition in QDs of various sizes. The known theoretical approaches for the stressed QD based on the use of perturbation theory [13] and the k p method [14] were restricted to the obtainment of the dependence of the radiative transition energy E 0 on the pressure P and were used mainly for the description of the X -Γ intersection of the conduction band edges emerging at high pressures (42 kbar for the InAs QD). The first attempts to relate the baric coefficient K QD to the QD sizes (with the energy of the PL peak) were attempted in [11] with the use of the Frogley model and in [15] based on the atomic model of the field of valence forces.…”