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Effects of radiation-induced damage on performance of semiconductor devices - surface recombination velocity model
Radiation induced damage to semiconductor surfaces and effect on performance
Charge-carrier-selective interfaces between electrocatalyst particles and semiconductor light absorbers are critical for solar photochemistry but controlling their properties is challenging. Using thin films and nanoparticle arrays of Pt hydrogen-evolution catalysts on p-InP (a high-performance photocathode material), along with macroscopic and nanoscopic electrical and chemical analysis, we show how hydrogen alloying, the pinch-off effect for nanoscale contacts, and the formation of a native surface oxides all play different roles in creating charge-carrier-selective junctions. As a result, the new insights can be broadly applied to photocathodes, photoanodes, and overall water-splitting systems to control charge-carrier selectivity and improve performance.
Radiation damage on semiconductor surfaces and effects on performance
In an embodiment, a semiconductor device is provided that includes a lateral transistor device having a source, a drain and a gate, and a monolithically integrated capacitor coupled between the gate and the drain.
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Alkali pnictogen dichalcogenides–I–V–VI 2 or APnCh 2 –have been identified as promising semiconducting materials for energy conversion devices. However, the controlled nanoscale synthesis and our understanding of the effects of cation ordering and stereochemically active lone pairs on the structures of these ternary compounds remain underdeveloped. Here, we use solution-phase chemistry to synthesize a family of APnCh 2 materials, including LiSbSe 2 , NaSbS 2 , NaSbSe 2 , NaBiS 2 , and NaBiSe 2 . Our approach utilizes alkali metal hydrides (AH) or carboxylates, A(O 2 CR), PnPh 3 , and elemental chalcogens as synthetic precursors and oleylamine or 1-octadecene as solvents. Synthetic manipulation via fine-tuning of reaction temperature enables control over the degree of ordering caused by the Sb 5s 2 lone pair-induced distortions in NaSbS 2 . Pair distribution function analysis demonstrates that the structure of the Sb-containing phases deviates much more from a disordered rock salt structure than that of the Bi-containing phases. This local distortion, induced by the Sb lone pair, leads to a previously unreported noncentrosymmetric NaSbS 2 crystal structure, which is additionally supported by second-harmonic generation measurements. Infrared and multinuclear solid-state NMR spectroscopies show that oleylamine or chelating carboxylates and, in some cases, unreacted precursors (LiH and PnPh 3 ) remain bound to the nanocrystalline surfaces. Further, a deeper understanding of the local atomic environment, long-range ordering, surface chemistry, and optoelectronic properties of these materials may speed up their fundamental study and application.
We report a theoretical study of CdSe nanoplatelets aimed at identifying the main factors determining their photophysical properties. Using atomic configurations optimized with density functional theory calculations, we computed quasiparticle and exciton binding energies of nanoplatelets with two to seven monolayers. We employed many body perturbation theory at the GW level and solved the Bethe-Salpeter equation to obtain absorption spectra and excitonic properties. Our results, which agree well with recent experiments, were then used to design a model that allows us to disentangle the effects of quantum confinement, strain induced by passivating ligands, and dielectric environment on the electronic properties of nanoplatelets. We found that, for the model to accurately reproduce our first principle results, it is critical to account for surface stress and consider a finite potential barrier and energy-dependent effective masses when describing quantum confinement. Our findings call into question previous assumptions on the validity of an infinite barrier to describe carrier confinement in nanoplatelets, suggesting that it may be possible to optimize interfacial charge transfer and extraction by appropriately choosing passivating ligands. The model developed here is generalizable to core-shell platelets and enables the description of system sizes not yet directly treatable by first-principles calculations.
Lighting a route for hyperbolic dispersion The propagation of light within a material is usually well defined, with the propagation described by scattering and dispersion. In artificially designed metamaterials and in anisotropic layered materials, the dispersion can be hyperbolic, giving rise to subwavelength confinement of the light. Sternbach et al. show that the hyperbolic dispersion can be optically switched on and off on demand in the layered transition metal dichalcogenide tungsten diselenide (see the Perspective by Deng and Chen). Illuminating the material with ultrafast pulses of sub-bandgap light creates a transient waveguide, resulting in hyperbolic dispersion in the material. The ability to tune the dispersion characteristics on demand using optical pumping is an effective approach for developing ultrafast switching photonic devices and controlling the propagation of light on the nanoscale. Science , this issue p. 617 ; see also p. 572
This is the final report. The finished research was published in 27 journal papers listed below. The topics fall roughly into seven categories: Photochemistry of water at the GaN ($10\bar{1}0$) surface; Quasiparticles: Band electrons and Anharmonic phonons; Quasiharmonic theory; Anharmonic lattice thermal conductivity; Water and Ice; Electron-phonon effects; and, Alloy theory.
A technique for fabricating a semiconductor heterostructure by growth of a ternary semiconductor on a binary semiconductor substrate from a melt of the ternary semiconductor containing less than saturation of at least one common ingredient of both the binary and ternary semiconductors wherein in a single temperature step the binary semiconductor substrate is etched, a p-n junction with specific device characteristics is produced in the binary semiconductor substrate by diffusion of a dopant from the melt and a region of the ternary semiconductor of precise conductivity type and thickness is grown by virtue of a change in the melt characteristics when the etched binary semiconductor enters the melt.
A technique for fabricating a semiconductor heterostructure by growth of a ternary semiconductor on a binary semiconductor substrate from a melt of the ternary semiconductor containing less than saturation of at least one common ingredient of both the binary and ternary semiconductors wherein in a single temperature step the binary semiconductor substrate is etched, a p-n junction with specific device characteristics is produced in the binary semiconductor substrate by diffusion of a dopant from the melt and a region of the ternary semiconductor of precise conductivity type and thickness is grown by virtue of a change in the melt characteristics when the etched binary semiconductor enters the melt.