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We demonstrate a novel type of optical switching mechanism in pin separate confinement multiple quantum well (SCMQW) structures. By introducing additional large barriers into conventional InGaAs(P)/InP SCMQW structures, the transport of photogenerated holes can be controlled in such a way that they accumulate in the intrinsic region. This positive space charge leads to a local screening of the internal field in the optical confinement layer and to an enhancement of the internal field in the MQW region. We characterize the optical nonlinearity, which is based on the quantum confined Stark effect (QCSE), experimentally and theoretically. As the nonlinearity is observed at input powers <1 W/cm2 in the basic nonoptimized structures presented here, we propose to use our structure especially for low-power optical switches.

Layers of InP:Tm, GaAs:Tm, GaP:Tm, and GaInP:Tm have been grown by metal-organic vapor phase epitaxy at atmospheric pressure using tris(isopropylcyclopentadienyl)thulium as a liquid Tm source. Electrical measurements revealed no characteristic influence of Tm on the electrical properties of the semiconductor host. Tm3+-related 4f emissions at 1.2 and 1.9 μm are observed both in GaAs and GaInP. In GaAs, the Tm3+ 4f luminescence at 1.2 μm consists of a series of very sharp lines. In GaInP samples, the Tm3+-related luminescence at 1.2 μm is much stronger than in the GaAs samples and is still observable at room temperature.