Current-voltage characteristics of light-emitting diodes under optical and electrical excitation

AbstractWe report on the fabrication and characterisation gallium nitride light emitting diodes (LEDs) grown by molecular beam epitaxy on (0001) oriented sapphire and (111)B GaAs substrates. The current voltage characteristics of the devices grown on sapphire show turn on voltages of between 4 and 5V with large on-series resistance of 600Ω; for corresponding devices grown on GaAs these parameters are between 6 and 7V and 150 Ω, respectively.Room temperature electroluminescence (EL) spectra from the GaN LEDs ,grown on sapphire substrates, show a dominant emission at 3.2 eV (397nm) with a full width half maximum (FWHM) of 335 meV which is attributed to free electron to acceptor transitions (e, A−Mg). A broad low intensity deep level emission is also observed centred at 2.4 eV (506nm). The peak of the EL from the devices grown on GaAs is at 3.1eV rather than 3.2eV. The differences between the two sets of devices are probably caused by the different device geometry.Preliminary results show that an “annealing” effect caused by electrical stressing resulted in an improvement of the EL spectra. The stressed samples show an increase in the near band edge emission intensity, a 20meV reduction in the FWHM and a significant reduction in the intensity of the deep level emission. The devices have a large 1/f noise contribution which does not appear to change after electrical stressing.

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Neodymium-doped GaAs Light-emitting Diodes

MRS Proceedings ◽

10.1557/proc-422-351 ◽

1996 ◽

Vol 422 ◽

Author(s):

S. J. Chang

Keyword(s):

Quantum Efficiency ◽

Breakdown Voltage ◽

External Quantum Efficiency ◽

Light Emitting Diodes ◽

Light Emitting ◽

Current Voltage ◽

Current Voltage Characteristics ◽

Minority Carriers

Nd-doped semiconductor light-emitting diodes were fabricated by implanting Nd ions into a GaAs epi-layer. The fabricated GaAs:Nd diodes show good current-voltage characteristics with a typical reverse breakdown voltage between 8 and 12 V By injecting minority carriers into the diodes, Nd3+ related emissions were observed, at 77 K, in the 0.92, 1.11, and 1.3 μm regions. These electroluminescence signals correspond to the transitions from Nd3+4F3/2 state to the Nd3+4I9/2, 4I1/2, and 4I13/2 states, respectively. The measured external quantum efficiency of the GaAs:Nd diodes at 77 K, was 5 × 10−7.

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Current-Voltage Characteristics of Single Layer Polymer Light Emitting Diodes Under High Intensity Electrical Excitation

MRS Proceedings ◽

10.1557/proc-561-185 ◽

1999 ◽

Vol 561 ◽

Author(s):

B. Ruhstaller ◽

J.C. Scott ◽

P.J. Brock ◽

S.A. Carter

Keyword(s):

Electric Fields ◽

High Intensity ◽

Single Layer ◽

Electrical Excitation ◽

Light Emitting ◽

Light Emitting Devices ◽

Single Carrier ◽

Current Voltage ◽

Current Voltage Characteristics ◽

Polymer Light Emitting Devices

ABSTRACTWe study the current-voltage characteristics of both double and single carrier polymer light emitting devices in the high intensity electrical excitation regime. Single layer devices are investigated with the orange-emitting MEH-PPV as the active polymer. Performing very low duty (≈0.001 %) pulsed electroluminescence measurements with electric fields up to 1*109 V/m, we observe for the hole-dominated devices a space charge limited current with a saturating mobility and a saturating external quantum efficiency of 1%. For double carrier devices, the current starts to saturate in the high-field regime, appoaching Ohmic-like behavior. We report current densities of 100 A/cm2and brightnesses of 7*105 cd/m2. The spectral features are monitored below the onset of degradation.

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