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A detailed comparison is presented between a comprehensive theoretical model, which uses the linewidth as the only fitted parameter, and a consistent set of experimental data for (i) the electro-optical properties of quantum-well (QW) modulators and (ii) the input power versus output power characteristics of interband self-electro-optic-effect devices (SEEDs). The model, which is founded on basic principles, includes excitonic effects and employs the depletion approximation to relate the applied bias to the electric field and to phenomenologically approximate the internal quantum efficiency. It is shown that this model is able to emulate and predict the behavior of QW modulators and SEEDs very well.

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Abstruct-We have demonstrated self-aligned InGaP/GaAs heterojunction bipolar transistors (HBT's) with excellent dc, microwave, and noise performance. A 3 x 10 pm2 emitter finger device achieved a cutoff frequency of fr = 66 GHz and a maximum frequency of oscillation of fmax = 109 GHz. A minimum noise figure of 1.12 dB and an associated gain of 11 dB were measured at 4 GHz. These results are the highest combined fT + fmax and the lowest noise figure reported for an InGaP/GaAs HBT and are attributed to materia€ quality and the use of self-aligned base contacts. These data clearly demonstrate the viability of InGaP/GaAs HBT's for high-speed, low-noise circuit applications.

A monolithic quantum well infrared photodetector (QWIP) structure has been presented that is suitable for dual bands in the two atmospheric transmission windows of 3 – 5.3 μm and 7.5 – 14μm, respectively. The proposed structure employs dual stacked, strain InGaAs/AlGaAs and latticematched GaAs/AlGaAs quantum well infrared photodetector for mid wavelength and long wavelength detection. The response peak of the strain InGaAs/AlGaAs quantum well is at 4.9 μm and the lattice-matched GaAs/AlGaAs is at 10.5μm; their peak sensitivities are in the spectral regions of 3 – 5.3mu;m and 7.5 – 14μm. The peak responsivity when the dual-band QWIP is biased at 5 Volts is ∼0.065A/W at 4.9μm and ∼0.006A/W at 10.5μm; at this voltage the dual-band QWIP is more sensitive at the shorter wavelengths due to its larger impedance thus exhibiting wavelength tunability characteristics with bias. Additionally, single colored 4.9 and 10.5μm QWIPs were fabricated from the dual-band QWIP structure to study the bias-dependent behavior and also to understand the effects of growing the strain layer InGaAs/AlGaAs QWIP on top of the lattice-matched GaAs/AlGaAs QWIP. In summary, two stack dual-band QWIPs using GaAs/AlGaAs and strained InGaAs/AlGaAs multiquantum wells have been demonstrated with peak spectral sensitivities in the spectral region of 3 – 5.3μm and 7.5 – 14μm. Also, the voltage tunable dual-band detection have been realized for this kind of QWIP structure.