We explore the effects of surfactant-mediated epitaxy on the structural, electrical, and optical properties of fast metal-semiconductor superlattice photoconductors. Specifically, application of a bismuth flux during growth was found to significantly improve the properties of superlattices of LuAs nanoparticles embedded in In 0.53 Ga 0.47 As. These improvements are attributed to the enhanced structural quality of the overgrown InGaAs over the LuAs nanoparticles. The use of bismuth enabled a 30% increase in the number of monolayers of LuAs that could be deposited before the InGaAs overgrowth degraded. Dark resistivity increased by up to $15Â while carrier mobility remained over 2300 cm 2 /V-s and carrier lifetimes were reduced by >2Â at comparable levels of LuAs deposition. These findings demonstrate that surfactant-mediated epitaxy is a promising approach to enhance the properties of ultrafast photoconductors for terahert generation.

We describe how growth at low temperatures can enable increased active layer strain in GaSb-based type-I quantum-well diode lasers, with emphasis on extending the emission wavelength. Critical thickness and roughening limitations typically restrict the number of quantum wells that can be grown at a given wavelength, limiting device performance through gain saturation and related parasitic processes. Using growth at a reduced substrate temperature of 350 °°°°C, compressive strains of up to 2.8% have been incorporated into GaInAsSb quantum wells with GaSb barriers; these structures exhibited peak room-temperature photoluminescence out to 3.96 μm. Using this growth method, low-threshold ridge waveguide lasers operating at 20 °C and emitting at 3.4 μm in pulsed mode were demonstrated using 2.45% compressively strained GaInAsSb/GaSb quantum wells. These devices exhibited a characteristic temperature of threshold current of 50 K, one of the highest values reported for type-I quantum-well laser diodes operating in this wavelength range. This temperature stability is attributable to the increased valence band offset afforded by the high strain values, due to the simultaneously high quantum well indium and antimony mole fractions. Exploratory experiments using bismuth both as a surfactant during quantum well growth, as well as in dilute amounts incorporated into the crystal were also studied. Both methods appear promising avenues to surmount current strain-related limitations to laser performance and emission wavelength.

We report the room temperature photoluminescence and electroluminescence properties of boron incorporated into highly strained InGaAs, forming BGaInAs, grown on GaAs substrates. X-ray diffraction was used to determine the alloy composition and strain of BGaInAs quantum wells on GaAs. As expected, the addition of boron reduced the quantum well compressive strain, preventing strain-relaxation and enabling extension of the peak emission wavelength of InGaAs quantum wells to 1.3 μm on GaAs. We also report both the longest wavelength emission observed from BGaInAs (1.4 μm) and electrically injected photoemission from a dilute-boride active region. We observed a blueshift in electroluminescence, due to unintentional in situ annealing of the active region, which we mitigated to demonstrate a path to realize true 1.3 μm emitters in the presence of in situ annealing.

We differentiate the effect of strain induced by lattice-mismatched growth from strain induced by mechanical deformation on cubic nonradiative Auger recombination in narrow-gap GaInAsSb/GaSb quantum well (QW) heterostructures. The typical reduction in the Auger coefficient observed with lattice-mismatched growth appears to be due to the concomitant compositional change rather than the addition of strain, with implications for mid-IR semiconductor laser design. We induced a range of internal compressive strain in five samples from −0.90% to −2.07% by varying the composition during the growth and mechanically induced a similar range of internal strain in analogous quantum well membrane samples. We performed time-resolved photoluminescence and differential reflectivity measurements to extract the carrier recombination dynamics, taken at 300 K with carrier densities from 2.7×1018 cm−3 to 1.4×1019 cm−3. We observed no change with strain in the cubic Auger coefficient of samples that were strained mechanically, but we did observe a trend with strain in samples that were strained by the QW alloy composition. Measured Auger coefficients ranged from 3.0×10−29 cm6 s−1 to 3.0×10−28 cm6 s−1.

We explore the effects of surfactant-mediated epitaxy on the structural, electrical, and optical properties of fast metal-semiconductor superlattice photoconductors. Specifically, application of a bismuth flux during growth was found to significantly improve the properties of superlattices of LuAs nanoparticles embedded in In0.53Ga0.47As. These improvements are attributed to the enhanced structural quality of the overgrown InGaAs over the LuAs nanoparticles. The use of bismuth enabled a 30% increase in the number of monolayers of LuAs that could be deposited before the InGaAs overgrowth degraded. Dark resistivity increased by up to ∼15× while carrier mobility remained over 2300 cm2/V-s and carrier lifetimes were reduced by >2× at comparable levels of LuAs deposition. These findings demonstrate that surfactant-mediated epitaxy is a promising approach to enhance the properties of ultrafast photoconductors for terahert generation.