Indium gallium nitride LED chips for the future of lighting

Indium gallium nitride, molecular formula InXGA1-XN. A ternary compound semiconductor formed by indium and gallium nitride. Is a direct bandgap semiconductor. The range of energy gap can be adjusted freely from 0.7 electron volts of indium nitride energy gap to 3.4 electron volts of gallium nitride energy gap with the change of indium fraction x in the alloy. It can be used to produce high efficiency solar cells and light emitting diodes. It is the essential material of active layer of modern blue light, green light and ultraviolet light emitting diodes.

Indium gallium nitride (InGaN) is the key material of blue LED

To make group III nitride leds emit red and green light in the RGB primary colors, the amount of indium in the indium gallium nitride Quantum Wells is typically increased. However, the latest research has found that traditional methods cannot produce efficient red and green leds. Despite advances in green-light leds and lasers, researchers have been unable to overcome the 30% limit of indium in gallium nitride, and it is unclear whether it is due to environmental or fundamental factors. Indium gallium nitride (InGaN) is the key material of blue LED.

To make group III nitride leds emit red and green light in the RGB primary colors, the amount of indium in the indium gallium nitride Quantum Wells is typically increased. However, the latest research has found that traditional methods cannot produce efficient red and green leds.

Despite advances in green-light leds and lasers, researchers have been unable to overcome the 30% limit of indium in gallium nitride, and it is unclear whether it is due to environmental or fundamental factors. An international team of researchers from Germany, Poland and China has explained the problem of indium limitation and further explained the mechanism of this limitation.

An international team of researchers from Germany, Poland and China has explained the problem of indium limitation and further explained the mechanism of this limitation.

Challenge scientists, according to the study of indium content limit, so the gallium nitride (GaN) grown on indium nitride (InN) single atomic layer, but the result of the experiment showed that the concentration of the indium content has remained at 25% to 30%, and could not continue to rise, it shows limited indium content is not affected by the environment, but the InN itself restriction mechanism.

The researchers used advanced Transmission Electron microscopy, or TEM, and Reflection high-energy Electron Diffraction, RHEED et al. showed that when the content of indium reached 25%, indium gallium nitride monolayer presented regular arrangement distribution, that is, indium single atomic column and two gallium atomic columns were alternately arranged.

A combination of inferential calculations showed that the ordering of atoms was affected by the specific surface reconstruction. Instead of bonding to three atoms, indium bonded to four of its neighbors, resulting in stronger chemical bonds between indium and nitrogen. This property allows indium gallium nitride to be grown at higher temperatures and with better material quality.

However, the amount of indium in this order only reaches 25%, a limitation that cannot be overcome under normal growth conditions.

Dr Tobias Schulz, a member of the research team, said the limited amount of indium meant that indium nitride could not excite red and yellow-green light, so a new approach was needed.