|
Progress of information technology in recent years has led to a rapid expansion in data communication capacity and there has been a strong demand for constructing cost-effective and high-performance optical communication systems. Photonic integrated circuit (photonic IC) technology has offered solutions for these requirements by eliminating the individual packaging and optical connections between devices. This approach is expected not only to reduce the cost, size, and power consumption but also to realize new functions that can never be possible with conventional discrete devices. For the practical use of photonic ICs, it is desirable that they can be used under uncooled conditions and are highly productive. However, it seems difficult for conventional InP-based devices to satisfy these requirements because their temperature characteristics are insufficient due to a weak electron confinement in the active region. In addition, at present, InP substrates used for production are mainly 2 or 3 inches in diameter and it is difficult to enlarge the wafer size with maintaining the quality and mechanical strength. GaInNAs, which has been developed recently as an alternative semiconductor material in the long-wavelength region, seems to be the best candidate to satisfy these requirements. It covers bandgaps corresponding to the wavelength from 1.3 μm to 1.6 μm with lattic-matched to GaAs, which leads to the following advantages. First low-cost and large-scale integrations can be realized with high productivity due to the usage of large GaAs substrates of up to 6 inches in diameter and well-established Ga-As-based process technology. Second as well known in GaInNAs lasers, much stronger electron confinement in the active layer can be realized. Therefore GaInNAs-based devices are expected to have larger gain and better temperature characteristics comparing with conventional InP-based devices. In addition, the low Auger recombination rate and large effective mass of electron would also improve gain and temperature characteristics. The crystal quality of GaInNAs has been improved rapidly in several years. Threshold current densities of GaInNAs lasers have been reduced more than one figure and both molecular beam epitaxy (MBE) and organometallic vapor phase epitaxy (OMVPE) can provide high quality GaInNAs as shown in figure 1. The threshold current density reached 200A/cm2 level at 1.3 μm region which is low enough to be used for practical applications. Therefore GaInNAs is thought to be a key material in photonic ICs in the long wavelength region. Semiconductor lasers and semiconductor optical amplifiers (SOAs) are key components of photonic ICs functioning as light sources, switches, amplifiers, wavelength converters and so on. In this paper, as the first study for photonic integration using GaInNAs, we present very low threshold current GaInNAs lasers and GaInNAs SOAs operating 1.3 μm region with good temperature characteristics.
|
