Structural study of defects induced during current injection to II–VI blue light emitter

Tomiya, Shigetaka; Morita, Etsuo; Ukita, M.; Okuyama, Hiroomi; Itoh, Satoshi; Nakano, K.; Ishibashi, Akira

doi:10.1063/1.113238

Cited by 74 publications

(21 citation statements)

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“…One can see the absence of dark spot defects and the subsequent ͗100͘ dark line defects which are usually observed and have previously been recognized as the principal cause for the rapid degradation of the active layer in II-VI laser diodes. [1][2][3][4] Instead of this, an increase in PL efficiency can be observed in the area previously submitted to intense optical excitation. As a comparison, Fig.…”

Section: ϫ2mentioning

confidence: 96%

“…[1][2][3][4] Considerable effort has been put into reducing the stacking fault density to less than the critical value of 10 4 cm Ϫ2 in order to obtain a laser diode with no extended defects in its stripe area ͑typically, 10 mϫ600 m͒. At present, a 100 h lifetime continuouswave laser diode operating at room temperature has been achieved with a stacking fault density lower than 3 ϫ10 3 cm…”

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confidence: 99%

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Defect annealing in a II–VI laser diode structure under intense optical excitation

Jordan

Fewer

Donegan

et al. 1998

Applied Physics Letters

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Defect annealing under intense pulsed optical excitation has been observed in a II-VI laser diode structure at room temperature. More than one order of magnitude increase in photoluminescence intensity has been obtained when the annealed area is probed at low excitation intensity. High-resolution confocal photoluminescence images of the annealed region do not show any sign of degradation. Together, these results suggest that an initial density of intrinsic point defects present within the active region can be removed by the optical annealing. Recombination-enhanced defect reactions in the vicinity of the point defects are responsible for this nonthermal annealing effect. © 1998 American Institute of Physics. ͓S0003-6951͑98͒00502-6͔Macroscopic defects originating at the GaAs/ZnSe heterointerface such as stacking faults and threading dislocations have been recognized to be the main cause of the rapid degradation and, therefore, the very short operating lifetime of II-VI-based laser diodes.1-4 Considerable effort has been put into reducing the stacking fault density to less than the critical value of 10 4 cm Ϫ2 in order to obtain a laser diode with no extended defects in its stripe area ͑typically, 10 mϫ600 m͒. At present, a 100 h lifetime continuouswave laser diode operating at room temperature has been achieved with a stacking fault density lower than 3 ϫ10 3 cm Ϫ2. 5 For further improvement, slower degradation mechanisms, such as point defect diffusion and reaction, need better understanding.It has been shown recently that recombination-enhanced defect reaction ͑REDR͒ is the driving force of the degradation in relatively long-lived II-VI light-emitting diodes. Recombination-enhanced processes in semiconductors have been thoroughly studied over the years.7-9 REDR describes how the energy released by nonradiative carrier trapping at point defect sites can excite localized vibrational modes of the defect and of the surrounding atoms, before being dissipated through lattice phonons. This energy can be used to promote defect motion and reaction, inducing defect multiplication ͑degradation͒, or, alternatively, defect reduction ͑annealing͒.In this letter we report an improvement in photoluminescence ͑PL͒ efficiency in a II-VI laser diode structure using high intensity laser excitation. Instead of observing degradation, we find that the PL efficiency increases as a function of time through optical annealing of the II-VI material. PL maps of the annealed area were also performed using a confocal microscope 10 setup ͑0.5 m resolution͒ and show that no degradation occurred in the active region during the annealing process.The sample studied was a ZnCdSe/ZnSSe/ZnMgSSe single quantum well separate-confinement heterostructure ͑SCH͒ grown by molecular beam epitaxy ͑MBE͒. The SCH structure is similar to the laser structure reported before, 5 except that a part of the p-type layer has been removed by chemical etching to allow optical pumping to be performed. The sample was annealed at room temperature by optical excitation using...

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Section: ϫ2mentioning

confidence: 96%

mentioning

confidence: 99%

Defect annealing in a II–VI laser diode structure under intense optical excitation

Jordan

Fewer

Donegan

et al. 1998

Applied Physics Letters

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“…Many researchers concentrated on the control of macroscopic defects such as stacking faults and dislocations which has induced so-called "rapid-degradation" [1][2][3]. At present, we succeeded in a elimination of these macrodefects from the active layer, resulting in improved blue-green LDs with device lifetime of over 500 h under room temperature CW operation [4].…”

Section: Introductionmentioning

confidence: 95%

Slow‐mode degradation mechanism and its control in new bright and long‐lived ZnSe white LEDs

Adachi

Ando

Abe

et al. 2006

Physica Status Solidi (b)

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This paper presents slow-mode degradation mechanism of ZnSe-based white LEDs. A systematic study has been made from a viewpoint of microscopic point defect reaction such as generation and migration in both device active layer (ZnCdSe/ZnSe MQW) and p-type ZnMgSSe cladding layer utilizing DLTS/ ICTS, SSRM (scanning spreading resistance microscope), and EL (electroluminescence)-imaging techniques, coupled with device aging experiments. We have found two different degradation stages (1st and 2nd stages) in the slow-mode degradation, which are caused by quite different microscopic point defect species. The 1st stage is induced by the long-diffusion of H0-center (nitrogen-complex deep hole trap in p-cladding layer), forming high-density dark-spots in the MQW active layer. This active center is generated only in the stress-stimulated condition such as thermal or device fabrication process. After controlling the initial concentration of the H0 center, we have observed no detectable new dark-spots during device operation, leading to fairly long device-lifetime (~1000 h). This 2nd stage has appeared as a carrier (hole) reduction in the p-type cladding layer. This final degradation stage is found to take place by an increase of shallow compensating donor-like centers in p-type cladding layer (ZnMgSSe). Based on these insights on the microscopic point defect reaction, we have developed (new) double cladding i-ZnMgBeSe/ p-ZnMgSSe white-LEDs, which has exhibited long device lifetime of over 10 000 h.

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“…The lattice mismatch is about 4.1 % [3], and such a large lattice would introduce defects at the heterointerface. Device performance of II-VI waveguide structures are very sensitive to defects, and macrodefects (dislocations or stacking faults) as well as microdefects could affect the device performance [4][5][6]. The prediction of the critical layer thickness (CLT) and the formation of defect free structures would be the key issue to realize high performance waveguide structures.…”

Section: Introductionmentioning

confidence: 99%

Growth and characterization of ZnMgTe/ZnTe layered structures grown by molecular beam epitaxy

Imada

Baba

Sakurasawa

et al. 2010

Phys. Status Solidi (c)

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ZnMgTe/ZnTe layered structures were grown on ZnTe substrates by molecular beam epitaxy, and the crystal structures were characterized using X‐ray diffraction methods. This structure would be the waveguide for various optoelectronic devices. Therefore, the crystal quality of this layered structure would be very crucial for the realization of high performance devices. ZnMgTe is lattice mismatched to ZnTe, and the increase of the ZnMgTe layer thickness or Mg mole fraction ratio would result in the crystal quality deterioration of the layered structure. The critical layer thickness (CLT) was theoretically derived, and various structures with various ZnMgTe layer thickness and Mg mole fraction were grown. The lattice mismatch strain relief and crystal quality of those samples were investigated by means of X‐ray reciprocal space mapping (RSM) and cross sectional transmission electron microscopy (TEM). The dislocation formation and the lattice mismatch relaxation were confirmed for various samples and it was revealed that the calculated CLT values could be used as an appropriate guideline to design the dislocation free and high performance device structures (© 2010 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

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Structural study of defects induced during current injection to II–VI blue light emitter

Cited by 74 publications

References 10 publications

Defect annealing in a II–VI laser diode structure under intense optical excitation

Defect annealing in a II–VI laser diode structure under intense optical excitation

Slow‐mode degradation mechanism and its control in new bright and long‐lived ZnSe white LEDs

Growth and characterization of ZnMgTe/ZnTe layered structures grown by molecular beam epitaxy

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