A key factor in improving quantum dots electrical properties and dots-based devices is the ability to control the crucial parameters of composition, doping, size, and strain distribution of the dots. We show that nanometer-scale work function measurements using ultrahigh vacuum Kelvin probe force microscopy is capable of measuring the strain and composition variations within and around individual QDs. This is accomplished by analyzing the detailed surface potential profiles in and around InSb/GaAs dots.

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A GaSb based homojunction interfacial work function internal photoemission far-infrared ͑Ͼ30 m͒ detector is presented. Metal-organic vapor phase epitaxy grown p-GaSb/ GaSb samples show 9.7 A / W peak responsivity and a peak detectivity of 5.7ϫ 10 11 Jones with effective quantum efficiency of 33% at 36 m and 4.9 K. The detector exhibits a 97 m ͑ϳ3 THz͒ free carrier response threshold wavelength. Results indicate that p-GaSb homojunction internal work function internal photoemission detectors are promising candidates to be a competitor for terahertz applications.

We have developed a midinfrared optical upconverter by wafer bonding a GaAs∕AlGaAs light-emitting diode with an InSb p+nn+ photodetector. The device converts midinfrared radiation in the range of 3–5.45μm to near-infrared light at 0.84μm, which can be efficiently detected using a widely available Si charge coupled device. At 77K, the measured external upconversion efficiency was 0.093W∕W. The optical up-conversion device, in combination with the Si CCD camera, leads to an alternative solution for making low-cost and large-area midinfrared imaging device. Effects of electrical gain and photon recycling inside this integrated device are discussed.

Composition, doping, size, and strain distribution within quantum dots, and at the dots-substrate interfaces, determine the confinement potential of electrons and holes creating a complex band structure. We use ultra-high vacuum Kelvin probe force microscopy to obtain the two-dimensional confinement potential in and around InAs and InSb dots epitaxially grown on GaAs. It is found that the potential manifests rich features governed by the strain and composition variations in the vicinity of the individual quantum dots. The results can adjust or confirm theoretical predictions for many epitaxial dots systems.