High indium composition In<sub>x</sub>Ga<sub>1-x</sub>As/GaAs quantum wells (x˃0.4) in which the well width reached to 7 nm without relaxing were grown on (100) GaAs substrates by MBE. The good crystal quality and optical properties of the high strained InGaAs/GaAs QW were obtained by controlling quasi-2D growth model and optimizing the growth condition including the growth temperature, growth rate, and V/III BEP ratio. Photoluminescence (PL) showed that the cutoff wavelength was about 1.3μm at room temperature with narrow full width at half maximum below 30meV. Dilute nitrogen and high In composition InGaAsN/GaAs QW extended wavelength infrared photodetectors at 1.3 and 1.55 μm were also realized.
Recently excellent infrared detectors have been demonstrated using InAs/GaSb superlattice materials sensitive at wavelength from 3um to greater than 32um. Using empirical tight binding method (ETBM), different structures as InAs(xML)/GaSb(8ML), (x=2, 4, 6, 8) and InAs(14ML)/GaSb(7ML) were designed for various cut-off wavelengths from short to long IR wavelength. These materials were grown by MBE with valved cracker cells for arsenic and antimony on p-type GaSb(001) substrates. The microstructure and the bandgap <i>Eg</i> were verified by high resolution X-ray diffraction and photoresponse spectra. The temperature dependence of <i>Eg</i> and photoresponse responsivity <i>Rv</i> were studied. The differential resistance under zero bias <i>R<sub>0</sub></i> in MWIR photodiode was measured up to 10<sup>6</sup> ohms. The ideality factor in the range of 1.5 to 2.1 indicates the generation-recombination current and surface leakage current are the dominant leakage in the depletion region. These results will promote InAs/GaSb superlattices infrared detectors research in multi-color from short to long wave IR application.
The short- and mid-wavelength infrared detectors based on short period type II superlattices (SLs) InAs
(2ML) / GaSb (8ML) and InAs (8ML) / GaSb (8ML) were grown by molecular-beam epitaxy on
semi-insulating GaAs substrates. An interfacial misfit mode AlSb quantum dot layer and a thick GaSb layer
were grown as buffer layers. Room-temperature optical transmittance spectra showed clear absorption edge at
~2μm and ~5μm. The 50% cutoff wavelength of the two photoconductors was 2.1μm and 5.05μm in
photoresponse at 77K respectively. The blackbody detectivity was beyond 2×10<sup>8</sup> cmHz<sup>1/2</sup>/W at 77K and 1×10<sup>8</sup>
cmHz<sup>1/2</sup>/W at room temperature with 8 V/cm bias.