Carrier relaxation inGaAsv-groove quantum wires and the effects of localization

Abstract

Carrier relaxation processes have been investigated in GaAs/AlGaAs v-groove quantum wires (QWRs) with a large subband separation (∆E ≃ 46 meV). Signatures of inhibited carrier relaxation mechanisms are seen in temperature-dependent photoluminescence (PL) and photoluminescenceexcitation (PLE) measurements; we observe strong emission from the first excited state of the QWR below ∼50 K. This is attributed to reduced inter-subband relaxation via phonon scattering between localized states. Theoretical calculations and experimental results indicate that the pinchoff regions, which provide additional two-dimensional confinement for the QWR structure, have a blocking effect on relaxation mechanisms for certain structures within the v-groove. Time-resolved PL measurements show that efficient carrier relaxation from excited QWR states into the ground state, occurs only at temperatures > ∼ 30 K. Values for the low temperature radiative lifetimes of the ground-and first excited-state excitons have been obtained (340 ps and 160 ps respectively), and their corresponding localization lengths along the wire estimated.

Longitudinal photocurrent spectroscopy of a single GaAs/AlGaAs v-groove quantum wire

“…We have performed time-resolved measurements on similar QWR structures and obtain low temperature lifetimes of ∼350 and ∼150 ps for the n = 1 and 2 states respectively [15], which supports the above conclusions. Above 30 K, we observe a decrease in the relaxation time of the n = 2 state to the ground state, which is also consistent with these measurements.…”

“…In figure 2 we present a PC spectrum taken at 10 K. The dotted vertical lines indicate the positions of photoluminescence (PL) features observed for the various groove structures [15]. The lines at 1.595 and 1.65 eV originate from e 1 -hh 1 and e 2 -hh 2 (n = 1, 2) recombination in the QWR respectively.…”

“…This expression has been used to fit the data points in figure 4; we assume τ r ≡ τ loc 350 ps [15]. From the data in figure 4(a), with resonant excitation of the QWR at 1.585 eV, we obtain values of M = 0.36 and an escape time τ esc = 1.9 ps for 400 mV bias (80 V cm −1 ).…”

Recombination dynamics in wurtzite InP nanowires

“…In this paper, we report a systematic study of the recombination dynamics of wurtzite InP NWs with an average diameter of 16 nm as a function of emission energy, temperature, and excitation fluence. In III-V systems, time-resolved photoluminescence ͑PL͒ has been used in the past to study one-dimensional structures such as V-groove [17][18][19][20] and etched 21 quantum wires as well as self-assembled quantum dash structures, 22 but few reports have mentioned the carrier dynamics in freestanding nanowires. 3,23 Other groups have performed time-resolved measurements on II-VI nanowires such as ZnO, 24 ZnSe, 25 and CdS, 26 revealing complex recombination dynamics in these structures.…”

Observation of high Rydberg states of one-dimensional excitons in GaAs quantum wires by magnetophotoluminescence excitation spectroscopy

“…15 Numerous studies have been conducted on the excitedexciton states in semiconductor quantum wires. 6,[16][17][18][19][20][21][22][23][24] The observed excited-exciton states consist of higher electron and higher hole subbands or different electron and hole subbands. The higher Rydberg states of the ground exciton, consisting of the first electron and the first hole subbands, are indistinguishable from the band edge and other possible excitedsubband transitions because of their small binding energies and broadening.…”