We propose the application of GaNAs as a novel material fabricated on a Si wafer. It is a direct-transition type semiconductor, and can be lattice-matched to Si. Therefore, it is valid for use in the active region of light-emitting devices fabricated on Si. In this letter, GaNAs with a low N content is grown on a GaAs wafer to explore the gas-source molecular beam epitaxy under which a N radical is used as the N source. As a consequence, GaNAs with a N content up to 1.5% is grown, even though the conductance of the N-radical beam cell is fixed at a very low value. The bowing parameter of the bandgap is experimentally evaluated at 18 eV.

We report an ultrafast cross phase modulation (XPM) effect in intersubband transition (ISBT) of InGaAs/AlAs/AlAsSb coupled quantum wells, where the ISBT absorption of a transverse-magnetic mode pump signal induces phase modulation of a transverse-electric mode probe signal. Using waveguide-type ISBT devices, we have achieved XPM-based 10 Gbit/s wavelength conversion with a power penalty of 2.53 dB. Also, we propose XPM-based signal processing circuits for gate switching and modulation format conversion.

We have developed a Mach-Zehnder interferometric all-optical switch employing intersubband transition in an InGaAs∕AlAs∕AlAsSb-coupled double quantum well waveguide. The recently discovered cross-phase modulation phenomenon was utilized as the switching mechanism; the nonlinear index of refraction for transverse electric polarized light is induced by intersubband optical excitation using transverse magnetic pump light. We demonstrate the demultiplexing operation of 160Gbit∕s data signals to 10Gbit∕s using this switch. At the input control pulse energy of 8pJ, the demultiplexed signals showed an extinction ratio better than 10dB, and an error-free demultiplexing was achieved.

InGaAs/AlAsSb quantum well structures have been grown by molecular beam epitaxy nominally lattice matched to InP substrates and characterized by photoluminescence. Growth interruptions at interfaces combined with selective group V species exposure were used. Our results indicate that interface quality: interface roughness as well as compositional variations involving group V sublattice species intermixing determine the nature of band alignment at heterointerfaces. The type I band lineup with band-edge discontinuity was estimated to be about 1.6 eV for As-terminated samples, which exhibit the lowest compositional fluctuations across heterointerfaces. The photoluminescence linewidths from InGaAs/AlAsSb quantum wells agree with linewidths calculated on the assumption of 1 ML fluctuations in well width. The inhomogeneous nature of the intermixed layers results in a large broadening of the luminescence spectra line shape for samples grown without termination or Sb termination.

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