Carrier relaxation bottleneck in type-II InAs/InGaAlAs/InP(001) coupled quantum dots-quantum well structure emitting at 1.55 μm

Abstract

Carrier relaxation in self-assembled InAs/In0.53Ga0.23Al0.24As/InP(001) quantum dots emitting at 1.55 μm and quantum dots coupled to the In0.64Ga0.36As/In0.53Ga0.23Al0.24As quantum well through a thin In0.53Ga0.23Al0.24As barrier is investigated employing high-temporal-resolution (< 0.3 ps), time-resolved spectroscopic techniques at cryogenic temperatures, supported additionally with photoluminescence, photoluminescence excitation, and theoretical modelling. We focused on intra-band carrier relaxation pathways that solely determine the observed non-equilibrium carrier population kinetics. We ascertained relatively fast carrier capture and intra-band relaxation process in a reference structure with quantum dots only (∼8 ps time constant) and even faster initial relaxation in the coupled system (∼4 ps). An evident bottleneck effect is observed for the final relaxation stage in the coupled quantum dots-quantum well system slowing down the overall relaxation process by a factor of 5. The effect is attributed to a peculiar picture of the confined conduction band states in the coupled system exhibiting significant changes in the spatial distribution between the relevant lowest-lying electronic states.

InP-Substrate-Based Quantum Dashes on a DBR as Single-Photon Emitters at the Third Telecommunication Window

“…Th tained PL decay time approximates well the radiative lifetime, which cor maximal single-photon emission rate of 0.5 GHz. However, this is just which is usually not achieved in the final SPS device due to the finite extr of the emission, nonideal internal quantum efficiency of the emitters, as w The photoluminescence lifetime and its accuracy determined from the fit with a monoexponential decay (red dotted line in Figure 3) is (1.78 ± 0.02) ns, which is similar to the values reported for other InAs on InP QD-like structures [20,51,60,63,[68][69][70]. The measurement was performed at low excitation power (0.1 µW) to minimize the probability of occupation of higher energy states, which would affect the PL lifetime.…”

Optical and electronic properties of symmetric InAs/InGaAlAs/InP quantum dots formed by a ripening process in molecular beam epitaxy: a promising system for broad-range single-photon telecom emitters

“…However, the uncertainty of experimental values does not allow this result to be verified. At the emission energy of 0.84 eV, a similar PL lifetime of ∼ 1.65 ns has been obtained for slightly in-plane asymmetric S-K InAs/InAlGaAs/InP(001) QDs [31]. For highly asymmetric confining potentials like those in InAs/InAlGaAs/InP(001) quantum dashes, the PL lifetime consists of two short and long components [30].…”

“…1 and shows two noticeable Δ𝑅/𝑅 features settled in the ranges of 1.13-1.20 eV and 0.92-0.96 eV, respectively. While the former is attributed to optical absorption involving valence and conduction bands of the InAlGaAs barrier [31], the latter is tentatively assigned to absorption in the WL. The WL-related feature appears to be constituted by at least two transitions centered at ∼0.93 eV and ∼0.94 eV.…”

Synthesis and systematic optical investigation of selective area droplet epitaxy of InAs/InP quantum dots assisted by block copolymer lithography

“…For a self-assembled InAs/GaAs QD the intra-band relaxation time reaches several ps [39]. In a very recent study on intra-band carrier relaxation times in selfassembled InAs/InP QDs it was shown that relaxation times can be as short as 8 ps at cryogenic temperatures, even including the capture time [40]. For a comparable QD system like InAs/InAlAs/InP(001) [41] and InAs/InP(311B) [42], or InAs/InGaAsP/InP(001) quantum dashes [43], the intra-band relaxation time is reported within the range of 1-40 ps.…”