In-Situ Tailoring of Vertically Coupled InAs p-i-p Quantum-Dot Infrared Photodetectors: Toward Homogeneous Dot Size Distribution and Minimization of In-Ga Intermixing

The authors report a detailed analysis of an epitaxial growth technique for indium arsenide (InAs) Quantum-dot infrared photodetectors circumvent the detrimental effects arising from the progressively increasing dot-size in vertically coupled heterostructures. Constant overgrowth percentage of the vertically coupled dot-layers has been achieved with the implementation of the growth strategy, which has been validated by cross-sectional transmission electron microscopy (X-TEM) images of the samples. The optical characteristics of these samples have been analyzed through photoluminescence spectroscopy and photoluminescence excitation spectroscopy (PL and PLE) measurements which show longer wavelength response and reduced full width at half-maxima (fwhm) upon implementation of the growth strategy. X-TEM and in-plane and out-of-plane high resolution X-ray diffraction (HR-XRD) measurements suggest morphological improvement upon implementation of the growth strategy, with a reduction in the indium desorption and lowering of defects and dislocation densities. Excellent correlation has been found between the different experimental results and also their theoretical simulations. The fabricated single-pixel photodetectors at low temperature (T = 14 K) show a broad response extending up to the MWIR region (similar to 4.5 mu m) for one of the samples. Also, a strong spectral response in the SWIR region is obtained even at room temperature (T = 300 K). The highest responsivity (R-p) and specific detectivity (D*) values obtained are 166.17 A/W and 8.39 x 10(10) cm Hz(1/2) W-1 at a bias of 5 V and 300 K temperature.