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Hossain, K.

Publications and source records attributed to Hossain, K..

5 records
All sourcesNASA NTRSDOE OSTI
DOE OSTI2016

High-density InAs/GaAs{sub 1−x}Sb{sub x} quantum-dot structures grown by molecular beam epitaxy for use in intermediate band solar cells

InAs quantum-dot structures were grown using a GaAs{sub 1−x}Sb{sub x} matrix on a GaAs(001) substrate. The use of GaAs{sub 1−x}Sb{sub x} for the buffer and cap layers effectively suppressed coalescence between dots and significantly increased the dot density. The highest density (∼3.5 × 10{sup 11}/cm{sup 2}) was obtained for a nominal 3.0 monolayer deposition of InAs with an Sb composition of x = 13–14% in the GaAs{sub 1−x}Sb{sub x} matrix. When the Sb composition was increased to 18%, the resulting large photoluminescent red shift (∼90 meV) indicated the release of compressive strain inside the quantum dots. For x > 13%, we observed a significant decrease in photoluminescence intensity and an increase in the carrier lifetime (≥4.0 ns). This is attributed to the type-II band alignment between the quantum dots and matrix material.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Short-wave infrared barriode detectors using InGaAsSb absorption material lattice matched to GaSb

Short-wave infrared barriode detectors were grown by molecular beam epitaxy. An absorption layer composition of In{sub 0.28}Ga{sub 0.72}As{sub 0.25}Sb{sub 0.75} allowed for lattice matching to GaSb and cut-off wavelengths of 2.9 μm at 250 K and 3.0 μm at room temperature. Arrhenius plots of the dark current density showed diffusion limited dark currents approaching those expected for optimized HgCdTe-based detectors. Specific detectivity figures of around 7×10{sup 10} Jones and 1×10{sup 10} Jones were calculated, for 240 K and room temperature, respectively. Significantly, these devices could support focal plane arrays working at higher operating temperatures.

71 CLASSICAL AND QUANTUM MECHANICS, GENERAL PHYSIC↗
DOE OSTI2015

Improved performance in GaInNAs solar cells by hydrogen passivation

The effect of UV-activated hydrogenation on the performance of GaInNAs solar cells is presented. A proof-of-principle investigation was performed on non-optimum GaInNAs cells, which allowed a clearer investigation of the role of passivation on the intrinsic nitrogen-related defects in these materials. Upon optimized hydrogenation of GaInNAs, a significant reduction in the presence of defect and impurity based luminescence is observed as compared to that of unpassivated reference material. This improvement in the optical properties is directly transferred to an improved performance in solar cell operation, with a more than two-fold improvement in the external quantum efficiency and short circuit current density upon hydrogenation. Temperature dependent photovoltaic measurements indicate a strong contribution of carrier localization and detrapping processes, with non-radiative processes dominating in the reference materials, and evidence for additional strong radiative losses in the hydrogenated solar cells.

75 CONDENSED MATTER PHYSICS, SUPERCONDUCTIVITY AND↗
DOE OSTI2013

Defect mitigation by ion induced amorphousization and solid-phase epitaxy

Ion implantation is a common technique in the semiconductor industry used to modify the electrical properties of materials, usually silicon. Some dopant ions are sufficiently light, such as boron, that they do not create a continuous amorphous layer in silicon over the range of the ions. In the presence of such a layer, most of the ioninduced damage can be removed by solid-phase epitaxy growth (SPEG), which results in recrystallization of the amorphous damage. However, end-of-range defects at the amorphous-crystal interface give rise to threading dislocations during SPEG that degrade the quality of the recrytallized Si. We have studied the end of range defects in silicon with three different implantations. The first was with 80 keV {sup 30}Si with a dose of 3 Multiplication-Sign 10{sup 15} Si/cm{sup 2}, and the second was with 100 keV {sup 72}Ge at a dose of 1 Multiplication-Sign 10{sup 15} Ge/cm{sup 2}, and the third was a double implant of 100 keV {sup 72}Ge at a dose of 1 Multiplication-Sign 10{sup 15} Ge/cm{sup 2} followed by 340 keV {sup 28}Si at a dose of 3 Multiplication-Sign 10{sup 14} Si/cm{sup 2}. SPEG was done at 650 Degree-Sign C to recrystalize the implanted samples, and the end of range defects were studied using channeled Rutherford Backscattering Spectrometry (RBS-c). The effects of photon-assisted hydrogenation on amorphization and recrystallization were also studied.

36 MATERIALS SCIENCE↗