Uniform Light Emission Research Articles

8.4: Extremely High Electron Emitting Properties of Self‐Organized Carbon Nano‐Tips

AbstractWe developed self‐organized carbon nano‐tips using a high density plasma CVD. A C2H2/H2 mixture was used as source gas for the deposition. The carbon nano‐tips showed good adhesion to the substrate and exhibited a turn‐on field as low as 0.1 V/μm and uniform light emission from a phosphor screen.

P‐44: Influences of Applied Writing Pulses on the Wall Charge Distribution and Light Output in AC Plasma Display Panels

AbstractThe influences of applied writing pulses on the wall charge distribution and light output for stable sustaining operation has been studied. The applied writing pulses, which have been selected, are the rectangular and the ramp shapes. The rectangular pulse shows strongly localized cone type of light emission profile, while the ramp pulse can makes a uniform box type light emission profile under the same coplanar AC‐PDP structure. It is shown that the ramp pulse can compensate the nonuniform electric field distribution across the whole electrode area. It is also found that the light emission characteristics from rectangular and ramp writing pulses are good agreement with theoretical wall charge set‐up models for these two writing pulses.

Temperature dependences of electroluminescent characteristics in the devices fabricated with novel triphenylamine derivatives

In this paper, we investigated the temperature dependences of the electroluminescent (EL) characteristics of two-layer devices fabricated using four hole-transporting materials based on triphenylamine, and a typical emitting material, tris (8-quinolinolato) aluminum. The thermal stability of the organic EL devices is clearly seen to depend on the glass transition temperature (T/sub g/) of the hole-transporting material. The EL device with a pentamer of triphenylamine exhibits uniform light emission in a continuous operation up to 155/spl deg/C without breakdown. A lowering of the turn-on voltage for light emission and an increase of luminous efficiency with increasing temperature are found in the devices. Excellent durability of continuous operation is also achieved at high temperatures. Our results indicate that the linear linkage of triphenylamine provides the high T/sub g/ material and the high device performance at high temperatures.

Controlled electroluminescence spectra of porous silicon diodes with a vertical optical cavity

It is demonstrated that a porous silicon (PS) optical cavity is available for the electroluminescence (EL) PS diode configuration. The PS diode is composed of a thin Au film, a light-emitting PS layer, a multilayered PS mirror, a p-type Si substrate, and an ohmic contact. When a sufficient bias voltage is applied to the diode, a uniform visible light emission is observed through the top contact. The EL intensity is fairly proportional to the driving current over a wide range of operation. The bandwidth of the EL spectrum is significantly reduced in comparison to that of the conventional PS diodes, owing to a resonance effect induced between the Au film and the multilayered PS mirror. These results suggest that the PS technology is a promising process for applications in monolithic integrated optoelectronics.

High-temperature operation of an electroluminescent device fabricated using a novel triphenylamine derivative

We have fabricated thermally stable organic electroluminescent (EL) devices using a hole transporting material, a tetramer of triphenylamine, and a typical emitting material, tris (8-quinolinolato) aluminum (Alq). The organic EL devices show uniform light emission in a continuous operation up to 140 °C without breakdown. A lowering of turn-on voltage for light emission and an increase of luminous efficiency with increasing temperature are found; the significantly low turn-on voltage of 2.1 V and the high luminous efficiency of 1.25 lm/W are obtained at 130 °C. Excellent durability of continuous operation is also achieved at the high temperature.

High reliability of AlGaInP LED's with efficient transparent contacts for spatially uniform light emission

The indium-tin oxide (ITO) films with low sheet resistance and conducting transparency have been used on the AlGaInP double-heterostructure orange light-emitting diodes (LED's) to improve the light extraction from the LED surface and device reliability. The orange LED's with ITO films exhibit a light output power of 1 mW at 50 mA, which corresponds to an external quantum efficiency of 1.1%. They can operate stably for more than 3000 h at 20 mA and 25/spl deg/C without any degradation.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

Visible Electroluminescence from Pn Junction Type μc-Sic/ Porous Si / c-Si Structures

ABSTRACTWe have fabricated two kinds of n-type microcrystalline silicon carbon (μc-SiC) / porous silicon (PS) / p-type crystalline silicon (c-Si) pn junctions and demonstrated a visible light emission from them. We have observed three types of visible light emission; an uniform red light emission at a forward current above 12mA/cm2 for the pn junction using a 0.2–0.4 Qcm c-Si substrate, and a very weak white light emission at a forward current of about 90 mA/mm2 and a strong orange-red light emission at a forward current from 200 to 619 mA/mm2for the pn junction using a 3.5–4.5 Ωcm c-Si substrate.

Electrical characterization of in-situ epitaxially grown Si p-n junctions fabricated using limited reaction processing

Forward current ideality factors of 1.01+or-0.3% were obtained over a large current range extending down to 1 pA. Reverse current densities measured 3.5+or-1.2 nA/cm/sup 2/ at a reverse bias of -5 V. Breakdown occurred at the expected value of -22 V and displayed a very sharp current rise of 30 decades/V. Extremely uniform light emission from the junction was observed under a microscope at breakdown, this phenomenon is a visual indication that the material is of high quality and suitable for high-performance minority-carrier devices.< <ETX xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">&gt;</ETX>

GaAs0.6P0.4LED's with efficient transparent contacts for spatially uniform light emission

Indium-tin oxide (ITO) and cadmium-tin oxide (CTO) transparent contacts have been used on GaAs 0.6 P 0.4 planar, red-light-emitting diodes. The entire emitting area of the diode can be contacted without blocking any of that area with opaque metal. Furthermore, the low sheet resistance of the transparent conducting films (2.5 to 3.5 ω/□) makes the spatial distribution of the emitted light more uniform. The spatial uniformity of the light output of LED's fabricated with transparent contacts is compared with that of conventional LED's. The current-voltage characteristics of the two types of LED are also compared. For an average current density of 25 A/cm2, an undesirable excess voltage (> 1.2 V) is developed across the reverse-biased (n-transparent conductor)-(p-GaAs 0.6 P 0.4 ) heterojunction. Procedures are described for reducing and, in some cases, completely eliminating this voltage by introducing a thin, transparent metal film between the transparent conductor and the GaAs 0.6 P 0.4 . The resulting devices have optical and electrical efficiencies comparable to those of conventional LED's.

Uniform Avalanche Effect in Silicon Three-Layer Diodes

Interaction of current gain and avalanche multiplication in three-layer diodes is utilized to produce uniform avalanche effect, indicated by uniform light emission over the area of a junction. Proof that the effect is caused by the three-layer action is furnished by removing the emitter layer, which changes the light emission to the usually observed microplasma pattern.