Since the transmission losses in quartz optical fibers has been reduced by reducing the numbers of hydroxyl (OH) groups, the minimum loss can be obtained at around 1.3 ?m and 1.55 ?m.1 These are therefore the wavelength region used for fiber communications. For quaternary InGaAsP III-V alloys in these wavelength regions, InP is an in dispensable material since it has good lattice matching with these alloys as seen in Fig. 1.12. InP is therefore a key material for the production of InP photonic devices such as laser diodes (LDs), light emitting diodes (LEDs) and photodetectors for this type of communication.2
InP is also promising for high frequency devices such as high-electron-mobility transistors (HEMTs) and hetero-bipolar-transistors (HBTs). Because the carrier concentrations and the electron mobilities are large enough in InGaAs layers lattice matching to InP, these InP-based devices can be used in the frequency range exceeding several tens of GHz.3 These devices are expected to be useful in new applications in millimeter wave communications, anticollision systems and imaging sensors.4 Opto electronic integrated circuits (OEICs) with the integration of lasers, photodetectors and amplifiers are indispensable for second generation communication systems working at 40 Gb/sec.5
Since InP has a band gap of around 1.4 eV with a high energy conversion efficiency, it is also promising for solar cells especially for space satellites, because of its high resistivity against radiation.6 In fact, InP based solar cells with p-n junctions have been fabricated for a space satellite.7
For the above applications,...
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