Article

Visible-Color-Tunable Light-Emitting Diodes

National Creative Research Initiative Center for Semiconductor, Nanorods, Department of Physics and Astronomy, Seoul National University, Korea.
Advanced Materials (Impact Factor: 15.41). 08/2011; 23(29):3284-8. DOI: 10.1002/adma.201100806
Source: PubMed

ABSTRACT Visible-color-tunable light-emitting diodes (LEDs) with electroluminescent color that changes continuously from red to blue by adjusting the external electric bias are fabricated using multifacetted GaN nanorods with anisotropically formed 3D InGaN multiple-quantum wells. Monolithically integrated red, green, and blue LEDs on a single substrate, operating at a fixed drive current, are also demonstrated for inorganic full-color LED display applications.

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    • "Another factor is the high dislocation density (10 9 –10 11 cm 2 ) of the epitaxial layer grown on the heterosubstrate, leading to a debasing influence on the device performance [7]. InGaN/GaN nanorods have been considered the most promising technique to reduce piezoelectric polarization by exposing the nonpolar planes (m-or a-planes) [8] [9] [10]. Furthermore, the increased effective emission area obtained by stretching the length of GaN nanorods can also potentially enhance the light output power [11]. "
    01/2014; 9(4):18-22. DOI:10.9790/1676-09411822
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    • "Therefore, to simplify the fabrication complexity associated with aforementioned techniques, it is extremely important to explore simpler approaches for multicolor displays. There have been several reports on different growth methods to achieve color tunability of inorganic LEDs and their potential in multicolor display and phosphor-free white lighting [12]–[14]. However, to the best of our knowledge, no multicolor inorganic display system has been realized based on these LED wafer materials. "
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    ABSTRACT: We demonstrate a color-tunable smart display system based on a micropixelated light-emitting diode $(muhbox{LED})$ array made from one InGaN epitaxial structure with high (0.4) indium mole fraction. When integrated with custom complementary metal–oxide–semiconductor (CMOS) electronics and a CMOS driving board with a field-programmable gate array (FPGA) configuration, this $muhbox{LED}$ device is computer controllable via a simple USB interface and is capable of delivering programmable dynamic images with emission colors changeable from red to green by tailoring the current densities applied to the $muhbox{LED}$ pixels. The color tunability of this CMOS-controlled device is attributed to the competition between the screening of piezo-electric field and the band filling effect. Comparable brightness of the $muhbox{LED}$ pixels emitting at different colors was achieved by adjusting the duty cycle. Further measurement suggests that this microdisplay system can also be used for high-speed visible light communications.
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    ABSTRACT: Nonpolar InGaN/GaN multiple quantum wells (MQWs) grown on the {11-00} sidewalls of c-axis GaN wires have been grown by organometallic vapor phase epitaxy on c-sapphire substrates. The structural properties of single wires are studied in detail by scanning transmission electron microscopy and in a more original way by secondary ion mass spectroscopy to quantify defects, thickness (1-8 nm) and In-composition in the wells (∼16%). The core-shell MQW light emission characteristics (390-420 nm at 5 K) were investigated by cathodo- and photoluminescence demonstrating the absence of the quantum Stark effect as expected due to the nonpolar orientation. Finally, these radial nonpolar quantum wells were used in room-temperature single-wire electroluminescent devices emitting at 392 nm by exploiting sidewall emission.
    Nano Letters 10/2011; 11(11):4839-45. DOI:10.1021/nl202686n · 13.59 Impact Factor
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