Decay Measurements of Free and Bound Exciton Recombination in Doped GaAs/GaAIAs Quantum Wells

1989 ◽  
Vol 163 ◽  
Author(s):  
J.P. Bergman ◽  
P.O. Holtz ◽  
B. Monemar ◽  
M. Sundaram ◽  
J.L Merz ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Temperature Dependence ◽  
Decay Time ◽  
Free Exciton ◽  
Temperature Decay ◽  
Photoluminescence Decay ◽  
Decay Times ◽  
Exciton Recombination

AbstractIn this study we present photoluminescence decay measurements of free exciton (FE) and bound exciton (BE) recombination in doped GaAs/AIGaAs quantum wells (QW). It is found that the FE decay time is reduced in the doped QW’s compared to similar undoped samples. The low temperature decay time of the BE is slightly longer than for the FE, with BE decay times from 300 to 600 ps for well widths of 50 to 150 Å, respectively. It is also found that the observed decay of the BE is strongly influenced by the decay time of the FE. This is especially observed in the similarity of the temperature dependence for the FE and BE decay time.

scholarly journals Radiative Lifetime of Excitons in GaInN/GaN Quantum Wells

1996 ◽  
Vol 1 ◽  
Author(s):  
Jin Seo Im ◽  
Volker Härle ◽  
Ferdinand Scholz ◽  
Andreas Hangleiter
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Decay Time ◽  
Elevated Temperatures ◽  
Radiative Lifetime ◽  
Thermal Dissociation ◽  
Interface Roughness ◽  
Nonradiative Recombination ◽  
Quantum Well Structures ◽  
Decay Times

We have studied GaInN/GaN quantum well structures grown by LP-MOVPE by picosecond time-resolved photoluminescence spectroscopy. For the quantum wells we find rather long PL decay times of up to 600 ps at low temperature. At temperatures higher than about 100 K, the decay time decreases rapidly, reaching about 75 ps at room temperature. From measurements of the integrated PL intensity, we conclude that this decrease of the decay time is due to nonradiative recombination processes. By combining our data for the lifetime and the intensity, we derive the radiative lifetime, which is constant at low temperature and increases at elevated temperatures. We explain this behavior on the basis of the interface roughness at low temperature and thermal dissociation of excitons at higher temperatures.

scholarly journals Quantum-Confined Stark Effect and Recombination Dynamics of Spatially Indirect Excitons in MBE-Grown GaN-AlGaN Quantum Wells

1999 ◽  
Vol 4 (S1) ◽  
pp. 375-380 ◽  
Author(s):  
Pierre Lefebvre ◽  
Bernard Gil ◽  
Jacques Allègre ◽  
Henry Mathieu ◽  
Nicolas Grandjean ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Electric Fields ◽  
Stark Effect ◽  
Quantum Confined Stark Effect ◽  
Indirect Excitons ◽  
Photoluminescence Decay ◽  
Decay Times ◽  
Low Temperature Photoluminescence ◽  
Recombination Dynamics

We analyze the low-temperature photoluminescence decay times, for a series of MBE-grown samples embedding GaN-AlGaN quantum wells. We investigate a variety of configurations in terms of well widths, barrier widths and overall strain states. We find that not only the wells but also the barriers are submitted to large built-in electric fields. In the case of narrow barriers (5 nm), these fields favor the nonradiative escape of carriers from narrow wells into wider wells. When all wells have the same width, the field in such narrow barriers allow us to observe the recombination of long-lived “inter-well” excitons at energies close to those of the short-lived “intra-well” excitons. Our results also prove that the energies and the dynamics of excitonic recombinations depend on the parameters of the heterostructures in a complicated way, due to the interplay of piezoelectric and spontaneous polarizations.

Dynamics of the Nitrogen Bound Excitons in 6H and 3C SiC

1994 ◽  
Vol 339 ◽  
Author(s):  
J. P. Bergman ◽  
C. I. Harris ◽  
O. Kordina ◽  
A. Henry ◽  
E. Janzén
Keyword(s):  
Decay Time ◽  
Low Temperatures ◽  
Strong Dependence ◽  
Free Exciton ◽  
Auger Process ◽  
Photoluminescence Decay ◽  
Donor Binding Energy ◽  
Decay Times ◽  
Exciton Decay ◽  
Exciton Decay Time

AbstractWe have measured the photoluminescence decay time of the bound excitons at the neutral nitrogen donors in the 6H and 3C polytypes of SiC. At 2K the decay times are 8.0 ns, 1.8 ns and 1.5 ns, for the P, R and S bound excitons in 6H SiC. For the nitrogen exciton in 3C, we find a decay time of 160 ns. These values are faster than previously reported for shallow donors in other indirect bandgap materials such as Si or GaP. Each of the observed decay times is found to be independent of the doping level in the sample, is temperature independent at low temperatures but decrease when the bound excitons are thermally ionised. The decay time related to different donor levels in 6H exhibits a strong dependence on the donor binding energy. We suggest that the dominant mechanism responsible for the observed decay time is a phonon-less Auger process. In high-purity 6H samples we have also measured the free exciton decay time at low temperatures to be 12 ns.

Quantum-Confined Stark Effect and Recombination Dynamics of Spatially Indirect Excitons in Mbe-Grown GaN-AlGaN Quantum Wells

1998 ◽  
Vol 537 ◽  
Author(s):  
Pierre Lefebvre ◽  
Bernard Gil ◽  
Jacques Allègre ◽  
Henry Mathieu ◽  
Nicolas Grandjean ◽  
...  
Keyword(s):  
Low Temperature ◽  
Quantum Wells ◽  
Electric Fields ◽  
Stark Effect ◽  
Quantum Confined Stark Effect ◽  
Indirect Excitons ◽  
Photoluminescence Decay ◽  
Decay Times ◽  
Low Temperature Photoluminescence ◽  
Recombination Dynamics

AbstractWe analyze the low-temperature photoluminescence decay times, for a series of MBE-grown samples embedding GaN-AlGaN quantum wells. We investigate a variety of configurations in terms of well widths, barrier widths and overall strain states. We find that not only the wells but also the barriers are submitted to large built-in electric fields. In the case of narrow barriers (5 um), these fields favor the nonradiative escape of carriers from narrow wells into wider wells. When all wells have the same width, the field in such narrow barriers allow us to observe the recombination of long-lived “inter-well” excitons at energies close to those of the short-lived “intra-well” excitons. Our results also prove that the energies and the dynamics of excitonic recombinations depend on the parameters of the heterostructures in a complicated way, due to the interplay of piezoelectric and spontaneous polarizations.

scholarly journals Photo- and cathodoluminescence investigations of piezoelectric GaN/AlGaN quantum wells

2000 ◽  
Vol 639 ◽  
Author(s):  
E.M. Goldys ◽  
M. Godlewski ◽  
M.R. Phillips ◽  
A.A. Toropov
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Electric Fields ◽  
Free Exciton ◽  
Multiple Quantum Well ◽  
Depth Profiling ◽  
Multiple Quantum ◽  
Recombination Mechanism ◽  
Decay Times ◽  
Piezoelectric Fields

ABSTRACTWe have examined multiple quantum well AlGaN/GaN structures with several quantum wells of varying widths. The structures had strain-free quantum wells and strained barriers. Strong piezoelectric fields in these structures led to a large red shift of the PL emission energies and long decay times were also observed. While the peak energies could be modelled using the effective mass approximation, the calculated free exciton radiative lifetimes were much shorter than those observed in experiments, indicating an alternative recombination mechanism, tentatively attributed to localised excitons. Cathodoluminescence depth profiling revealed an unusually small penetration range of electrons suggesting that electron-hole pairs preferentially remain within the multiple quantum well region due to the existing electric fields. Spatial fluctuations of the cathodoluminescence intensity were also observed.

scholarly journals Carrier trapping effects on photoluminescence decay time in InGaN∕GaN quantum wells with nanocluster structures

2007 ◽  
Vol 101 (6) ◽  
pp. 063511 ◽  
Author(s):  
Yen-Cheng Lu ◽  
Cheng-Yen Chen ◽  
Hsiang-Chen Wang ◽  
C. C. Yang ◽  
Yung-Chen Cheng
Keyword(s):  
Quantum Wells ◽  
Decay Time ◽  
Carrier Trapping ◽  
Photoluminescence Decay ◽  
Trapping Effects

Optical Spectroscopy of Defects in GaAs/AlGaAs Multiple Quantum Wells.

1993 ◽  
Vol 325 ◽  
Author(s):  
B. Monemar ◽  
P. O. Holtz ◽  
J. P. Bergman ◽  
Q.X. Zhao ◽  
C.I. Harris ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Optical Spectroscopy ◽  
Thermal Emission ◽  
Deep Level ◽  
Free Exciton ◽  
Interface Roughness ◽  
Multiple Quantum ◽  
Nonradiative Recombination ◽  
Decay Times ◽  
Bulk Semiconductors

AbstractThe study of electronic properties of GaAs/AlGaAs quantum wells (QWs) has traditionally been focused on intrinsic phenomena, in particular the free exciton behaviour. Defects and impurities have often been regarded as less relevant compared to the case of bulk semiconductors. Doping in QWs is important in many applications, however, and recently the knowledge about the structure of shallow donors and acceptors from optical spectroscopy has advanced to a level comparable to the situation in bulk semiconductors. A dramatic difference from the bulk case is the common occurrence of localisation effects due to interface roughness in QW structures. The recombination of bound excitons (BEs) differs drastically from bulk, BE lifetimes decrease with decreasing well thickness Lw, but increase with decreasing barrier thickness Lb (at constant Lw) below Lb=70Å. Exciton capture at impurities is a process which is strongly influenced by the localisation potentials from the interface roughness. The recombination process in doped QWs involves a nonradiative component, for shallow acceptors an excitonic Auger process has been identified. Deep nonradiative defects in the (MBE grown) QW as well as in the barrier material are manifested in measurements of the PL decay time vs temperature. In undoped multiple QWs the decay times vs T are consistent with thermal emission out of the well into the barrier, where nonradiative recombination via deep level defects occur. Nonradiative recombination in the well itself can be studied in electron-irradiated structures. Preliminary data also demonstrate the feasibility of hydrogen passivation of dopants as well as deep levels in the QW structures.

scholarly journals Photoluminescence of 8H-SiC

2013 ◽  
Vol 740-742 ◽  
pp. 347-350 ◽  
Author(s):  
Anne Henry ◽  
Ivan G. Ivanov ◽  
Erik Janzén ◽  
Tomoaki Hatayama ◽  
Hiroshi Yano ◽  
...  
Keyword(s):  
Binding Energy ◽  
Low Temperature ◽  
Band Gap ◽  
Free Exciton ◽  
Photoluminescence Spectroscopy ◽  
Ionization Energies ◽  
Nitrogen Levels ◽  
Excitonic Band ◽  
Exciton Recombination

8H-SiC epilayers grown on small 8H-SiC Lely platelets are investigated optically using photoluminescence spectroscopy. At low temperature the near band gap emission detected in the 2.78 to 2.67 eV range contains sharp lines associated to nitrogen-bound-exciton recombination. Three different no-phonon lines are detected accompanied by their phonon replicas. Free-exciton replicas are also observed which allows the determination of the excitonic band gap. The binding energy of the bound excitons can thus be determined and the ionization energies of the three nitrogen levels in 8H-SiC are estimated and found to be rather shallow compared to the values for other hexagonal polytypes. Additional bound-exciton lines are observed when the experimental photoluminescence temperature is increased.

Exciton localization behaviour in different well width undoped GaN/Al0.07Ga0.93N nanostructures

2007 ◽  
Vol 15 (3) ◽  
Author(s):  
M. Sabooni ◽  
M. Esmaeili ◽  
H. Haratizadeh ◽  
B. Monemar ◽  
P. Paskov ◽  
...  
Keyword(s):  
Quantum Wells ◽  
Decay Time ◽  
Photo Luminescence ◽  
Peak Position ◽  
Emission Peak ◽  
Time Resolved ◽  
Exciton Localization ◽  
Decay Times ◽  
Detection Energy ◽  
Hole Transition

AbstractWe report results from optical spectroscopy such as photoluminescence (PL) and time resolved photo-luminescence (TRPL) techniques from different well width MOCVD grown GaN/Al0.07Ga0.93N MQW samples. There is evidence of localization at low temperature in all samples. The decay time of all samples becomes non-exponential when the detection energy is increased with respect to the peak of the emission. Localization of carriers (excitons) is demonstrated by the “S-shape” dependences of the PL peak energies on the temperature. The time-resolved PL spectra of the 3-nm well multi quantum wells reveal that the spectral peak position shifts toward lower energies as the decay time increases and becomes red-shifted at longer decay times. There is a gradient in the PL decay time across the emission peak profile, so that the PL process at low temperatures is a free electron-localized hole transition.

scholarly journals Photoluminescence measurements on GaN/AlGaN modulation doped quantum wells

1999 ◽  
Vol 4 (1) ◽  
Author(s):  
J. Dalfors ◽  
J. P. Bergman ◽  
P.O. Holtz ◽  
B. Monemar ◽  
H. Amano ◽  
...  
Keyword(s):  
Quantum Well ◽  
Quantum Wells ◽  
Electron Gas ◽  
Energy Transition ◽  
Photoluminescence Spectra ◽  
Photoluminescence Decay ◽  
Fermi Edge ◽  
Decay Times ◽  
Piezoelectric Field ◽  
Good Agreement

Photoluminescence spectra were measured for 100 Å wurtzite GaN AlGaN modulation doped quantum wells. Three well-resolved peaks originate from the quantum well. The theoretically calculated confinement energies have been compared to the experimental energy positions and found to be in good agreement with the data, assuming that the piezoelectric field is largely screened by the electron gas. The highest energy transition may originate from the Fermi edge, consistent with the temperature dependence of the photoluminescence. Decay times for the different transitions indicate that the photoexcited holes are localized.

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