The explosive growth of Internet/intranet traffic has created a strong demand for cost-effective high-speed light-sources to be used in local access networks and data links. The frequency of relaxation oscillation (fr) is a major factor that restricts the high-speed operation of laser diodes. To achieve a high fr, the material of an active layer should have a large differential gain. By using GaInNAs, very deep quantum wells, especially in the conduction band can be formed. Deep quantum wells bring a large differential gain. In this paper, we show how GaInNAs lasers can be applied in this application
Since we first proposed the use of GaInNAs active layers to improve the high-temperature performance of long wavelength lasers in 1995, this material has been intensively investigated by many research groups and several promising results have been reported. We have used gas-source molecular beam epitaxy with N-radicals as a N-source for GaInNAs growth, and improved the crystal quality by optimizing the growth condition. Our growth method has the advantages of relative low temperature growth and a high N- radical sticking coefficient compared to metal organic chemical vapor deposition with Dimethylhydrazine. The effects of thermal annealing on the optical properties of GaInNAs layers have also been investigated. In-situ thermal annealing at temperatures above 550 degree(s)C was found to greatly enhance the photoluminescence intensity of GaInNAs. By optimizing both the crystal growth and thermal annealing conditions, we made a 1.3-micrometers GaInNAs/GaAs single-quantum- well laser that has a high characteristic temperature over 200 K and offers life time over 1000 hours. Therefore, we expect GaInNAs lasers to be put into practical use in the near future.
GaInNAs is a novel laser diode active layer material which holds great promise for low-cost optical fiber transmission applications requiring emission wavelengths near 1.3 micrometers . GaInNAs permits the realization of a long-wavelength vertical-cavity laser grown directly on a GaAs substrate. Continuous-wave room-temperature photo-pumped laser oscillation has been demonstrated in vertical cavity laser designs employing single or multiple GaInNAs quantum wells, with lasing wavelengths as long as 1.256 micrometers . Electrically-injected devices have achieved pulsed operation at room temperature and above, with a minimum threshold current density of 3.1 kA/cm2, slope efficiency above 0.04 W/A, and output power above 5 mW for 45 micrometers -diameter devices. Threshold current has exhibited minimal dependence on temperature from 20 degrees C to 60 degrees C, and laser oscillation is observed for temperatures as high as 95 degrees C.
In this paper, we fully review our recent progress in GaInNAs/GaAs long-wavelength lasers. An excellent characteristic temperature was confirmed for the GaInNAs laser diodes with a 1.2-micrometer wavelength. A record high value (T0 equals 126 K) was obtained in the temperature range from 25 to 85 degrees Celsius. We have also succeeded in applying GaInNAs to long-wavelength laser didoes that lased under room-temperature continuous-wave operation in the 1.3- micrometer wavelength range suitable for optical fiber communications. The temperature dependence of the lasing wavelength was as low as 0.35 nm/degrees Celsius. Thus, we have experimentally demonstrated that the GaInNAs laser diodes are very promising for application in optical fiber communications to overcome the poor temperature behavior of the conventional InGaAsP-based long-wavelength lasers.
We propose a novel material: GaInNAs. It can be formed on a GaAs substrate, and has a bandgap energy suitable for long- wavelength-range laser diodes. The band lineup is ideal for preventing electron overflow. Therefore, applying GaInNAs to long-wavelength-range laser diodes is expected to result in excellent high-temperature performance. We have succeeded in demonstrating continuous-wave operation of GaInNAs/GaAs single quantum well laser diodes at room temperature. The threshold current density was about 1.4 kA/cm2. The lasing wavelength was about 1.2 micrometers . We have measured some characteristic parameters of the GaInNAs laser diode under pulsed operation. A high characteristic temperature (T0) of 127 K and a small wavelength shift per ambient temperature change of 0.48 nm/ degree(s)C were obtained. The experimental results indicate the applicability of GaInNAs to long-wavelength-range laser diodes with excellent high- temperature performance.
A1GaInP alloy grown by organometallic vapor phase epitaxy (OW/FE) was
examined with various optical spectroscopic techniques; photoluminescence,
electroref'lectance, Raman scattering, extended X-ray absorption fine
structure, and with electron microscopy. It turns out that the band gap
shrinkage observed in AlGaInP is caused by deviation of atomic position from
the lattice sites of the normal zinc-blende lattice which is effected by the
interaction of random distribution structure and long-range ordering. The
long-range ordering is found to be specific to the (100) substrate plane.
Anomally in low temperature photoluminescence which may be related to long-
range ordering is also reported.
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