For decades, InP (indium phosphide) based lasers have dominated the optical communication market especially for long haul. This is because it was believed that there was no other material lattice matched to GaAs (gallium arsenide) that can emit > 1.1 micron. However, InP is very expensive. As a result, the cost to setup a modern MAN or LAN is simply too high because it requires tens of millions of lasers.
Around 1995, Kondow et al have proposed a new material called GaInNAs (gallium indium nitride arsenide) which capable of emitting light at 1.3 micron. This material is also called dilute nitride because a very low percent of Nitrogen is incorporated in the material. Because this new material can be grown on GaAs substrate which is considerably cheaper than InP (InP substrate cost 3x) and has greater conduction band offset which lead to better carrier confinement hence, can operate at higher temperature, dilute nitride has become a centre of attention among researchers in the world.
Besides, the established GaAs/AlAs mirror for DBR also can be incorporated with dilute nitride to design a VCSEL because the material is lattice matched to GaAs. High power pump lasers for Raman amplifier also can be further developed due to greater conduction band offset of dilute nitride.
However, there are lots of challenges that need to be tackled before dilute nitride based devices can penetrate the market. The incorporation of Nitrogen has significantly degrade the quality of the material. Therefore, high percentage of N cannot be incorporated to push the wavelength up to 1.55 micron. It was reported that Sb (antimony) can be used to keep the material grow in 2D and allows for higher N incorporation. However, the role of Sb and how it affects the bandgap is still unknown.
Besides, the usage of different material for the quantum well barrier also has proven to help reducing the bandgap. Material such as GaNAs or GaInNAs with different composition can be used instead of GaAs barrier.
Based on current research, dilute nitride based devices are far from being optimised. This is because this technology is largely material and knowledge limited. New knowledge on growth, material fundamentals and defect in arsenide-nitride are essential to bring this technology forward.
Around 1995, Kondow et al have proposed a new material called GaInNAs (gallium indium nitride arsenide) which capable of emitting light at 1.3 micron. This material is also called dilute nitride because a very low percent of Nitrogen is incorporated in the material. Because this new material can be grown on GaAs substrate which is considerably cheaper than InP (InP substrate cost 3x) and has greater conduction band offset which lead to better carrier confinement hence, can operate at higher temperature, dilute nitride has become a centre of attention among researchers in the world.
Besides, the established GaAs/AlAs mirror for DBR also can be incorporated with dilute nitride to design a VCSEL because the material is lattice matched to GaAs. High power pump lasers for Raman amplifier also can be further developed due to greater conduction band offset of dilute nitride.
However, there are lots of challenges that need to be tackled before dilute nitride based devices can penetrate the market. The incorporation of Nitrogen has significantly degrade the quality of the material. Therefore, high percentage of N cannot be incorporated to push the wavelength up to 1.55 micron. It was reported that Sb (antimony) can be used to keep the material grow in 2D and allows for higher N incorporation. However, the role of Sb and how it affects the bandgap is still unknown.
Besides, the usage of different material for the quantum well barrier also has proven to help reducing the bandgap. Material such as GaNAs or GaInNAs with different composition can be used instead of GaAs barrier.
Based on current research, dilute nitride based devices are far from being optimised. This is because this technology is largely material and knowledge limited. New knowledge on growth, material fundamentals and defect in arsenide-nitride are essential to bring this technology forward.
2 comments:
complicated...
how's ur study?
so far so good. but a bit slow at the moment. hopefully, i'll become busy in the next few weeks.
Post a Comment