| Indium Gallium Nitride |
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Indium gallium nitride is the light emitting layer in modern blue and green LED s and often grown on a GaN Buffer on a transparent substrate as, e.g. Sapphire or Silicon Carbide . It has a high Heat Capacity and its sensitivity to Ionizing Radiation is low (like other Group III Nitride s), making it also a potentially suitable material for Solar Cell arrays for Satellite s. InN does not mix homogenously with GaN. In a composition regime between ~ 15% -85% Indiumnitride Spinodal decomposition occurs leading to In-rich and Ga-rich InGaN regions or clusters. GaN is a defect rich material with typical dislocation densities exceeding 108 cm-2. Light emission from InGaN layers grown on such GaN buffers used in blue and green LEDs is expected to be low because of non-radiative recombination at such defects. Nevertheless InGaN Quantum Well s, are efficient light emitters in green, blue, white and Ultraviolet Light Emitting Diode s and Diode Laser s. In the indium-rich regions, with a lower bandgap than the surrounding material, most electron-hole pairs recombine and by the lower potential energy of these clusters carriers are hindered to diffuse and recombine non-radiatively at crystal defects. The wavelength emitted, dependent on the material's band gap, can be controlled by the GaN/InN ratio, from near ultraviolet for 0.02In/0.98Ga through 390 nm for 0.1In/0.9Ga, violet-blue 420 nm for 0.2In/0.8Ga, to blue 440 nm for 0.3In/0.7Ga, to red for higher ratios and also by the thickness of the InGaN layers which are typically in the range of 2-3 Nm . This defect tolerance, together with a good spectral match to sunlight, also makes the material suitable for Solar Cell s. It is possible to grow multiple layers with different bandgaps, as the material is relatively insensitive to defects introduced by a lattice mismatch between the layers. A two-layer multijunction cell with bandgaps of 1.1 EV and 1.7 eV can attain a theoretical 50% maximum efficiency, and by depositing multiple layers tuned to a wide range of bandgaps an efficiency up to 70% is theoretically expected. {Link without Title} Quantum Heterostructure s are often built from GaN with InGaN active layers. InGaN is often used together with other materials, eg. GaN , AlGaN , on SiC , Sapphire and even Silicon etc. SEE ALSO |
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