A research group headed by Prof. Niu Zhichuan from the State Key Laboratory for Semiconductor Superlattice and Microstructures affiliated to the CAS Institute of Semiconductors has succeeded in developing a GaAs-based long-wavelength laser device: InAs/GaAs self-assembly quantum dot laser with lasing wavelength of 1.33 µm under continuous-wave operation mode at room temperature. Experts say this is the most important achievement in the field of GaAs-based near-infrared, long-wavelength materials and devices in China in recent years.
It is known that in the near future the optical fiber communication network will be dominated by opto-electronic integrated devices in order to meet the increasing demands for higher-speed, more reliable and stable operation of data transferring and processing systems. The technology of opto-electronic integrated devices now becomes a hot topic in the world.
At present, the main devices widely used in the current optical fiber communication network are made by InP-based materials. However, due to a host of major difficulties, encouraging progress for further extending their application ranges are not expected at least for the time being.
Therefore it is in urgent need of developing new functional materials. GaAs-based semiconductors are acting as a good choice for developing such devices. The most important kinds of GaAs-based semiconductor materials working for near-infrared wavelength from 1.2 to 1.7µm are in the form of InAs self-assembled quantum dots, GaInNAs and GaInNAsSb quantum wells. The quantum dot structures attract scientists for their top performance as they excel in a high-speed operation with lower power consumption and new functions. The quantum wells are new multi-element compounds noted for their temperature stability. In recent years, these new semiconductor materials became a research focus in the most developed Western countries.
Since the end of the 1990s, a special research group headed by Prof. Niu at the CAS Institute of Semiconductors was funded for their work in the field. In order to speed up the research tempo, the team is composed of researchers from various fields ranging from material growth, physics analysis to device technology.
The researchers so far have been passing through three stages in their exploration. The first step for their success was the breakthrough attained before 2000 in the technology of molecular beam epitaxy of the InAs-bsed quantum dots lasers for the 0.9-1.1 µm wavelengths. By 2002, in the second stage, they succeeded in acquiring the 1.3µm quantum dots with high uniformity and high photoluminescence efficiency at room temperature. Their work was in the limelight of the international community when a world record was made. The newest development in their research was achieved in the latest two years. This includes the solution of a knotty problem in the growth of such quantum dots with long wavelength over 1.35 μm and high-density over 4.0E+10/cm2, and the fabrication technology of InAs/GaAs quantum dots lasers under continuous-wave operation mode at 1.33 µm at room temperature. This is the first research breakthrough achieved by Chinese scientists in developing long wavelength GaAs-based lasers in China. The success comes from their mastery of the core technology to grow long-wavelength and high-density quantum dots and the development of new expertise in fabrication of the laser devices.
At present, they are advancing in optimization of the 1.3 µm lasers in a bid to realize its practical application, and at mean time in developing of new types of GaAs-based quantum wells. Several new progresses have been developed: the emission wavelength of InGaAs/GaAs quantum wells created new international record up to 1.25 µm at room temperature; a patented technology of Gas Source Instantaneous Control Technique independently developed and succeeded in growing new GaInNAs quantum well materials with emission wavelength up to 1.31-1.42 µm at room temperature; a theoretical model for depicting the emission mechanism of the GaInAsNSb quantum well and superlattice has been proposed; room temperature 1.31 µm GaInAs/GaAsSb laser devices are realized and expected to expand the wavelength to 1.55 µm.
The research work is one of the hottest topics in today's highly competitive field of optical fiber communication systems in the world. Based on the research achievements attained by Chinese scientists as mentioned above, it is expected that in the near future the Chinese scientists will take lead in the further development of next generation GaAs-based long wavelength opto-electronic materials and devices for industrial application.
