InGaN

InGaN is a semiconductor alloy of indium nitride and gallium nitride, commonly written as In_xGa_{1−x}N, where x denotes the indium content. By varying composition, the material’s band gap can be tuned, enabling emission from near-ultraviolet to the green region. Increasing indium content lowers the band gap and shifts emission toward longer wavelengths, while low indium content yields shorter wavelengths similar to GaN.

The material has a wurtzite crystal structure and is typically grown by metal-organic chemical vapor deposition (MOCVD) or molecular beam epitaxy (MBE) on GaN substrates or templates. Incorporating indium is challenging because indium nitride has different growth dynamics and is more volatile at the temperatures needed for GaN, which can cause compositional inhomogeneity, strain, and defects. Lattice mismatch between the InGaN alloy and the GaN base can lead to strain and phase separation, especially at higher indium contents.

InGaN is central to modern optoelectronics, especially blue and green light-emitting devices. It forms the active region of blue and green LEDs and is used in laser diodes. White light emission is commonly achieved by combining blue InGaN LEDs with phosphors. The material also finds use in photodetectors and emerging ultraviolet devices. Key challenges include achieving stable high indium incorporation, mitigating polarization-related effects in the wurtzite lattice, and reducing efficiency droop at high operating currents. Ongoing research focuses on improving material quality, growth control, and device performance.