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Search indexed NASA NTRS and DOE OSTI research on propulsion, heat transfer, battery materials and energy systems. Follow report and document links to the original sources.

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At least 37 records · Page 2
All sourcesNASA NTRSDOE OSTI
NASA NTRS1992

Growth of a delta-doped silicon layer by molecular beam epitaxy on a charge-coupled device for reflection-limited ultraviolet quantum efficiency

Low-temperature silicon molecular beam epitaxy is used to grow a delta-doped silicon layer on a fully processed charge-coupled device (CCD). The measured quantum efficiency of the delta-doped backside-thinned CCD is in agreement with the reflection limit for light incident on the back surface in the spectral range of 260-600 nm. The 2.5 nm silicon layer, grown at 450 C, contained a boron delta-layer with surface density of about 2 x 10 exp 14/sq cm. Passivation of the surface was done by steam oxidation of a nominally undoped 1.5 nm Si cap layer. The UV quantum efficiency was found to be uniform and stable with respect to thermal cycling and illumination conditions.

Hoenk, Michael E.↗
NASA NTRS2000

Delta-doped imagers for UV and EUV applications

In this paper we will discuss performance of delta-doped CCDs in UV and EUV, our in-house thinning capability, bonding approaches for producing flat focal plane arrays, and in-house capabilities of directly applied antireflection coatings.

UV EUV delta-doped imagers↗
NASA NTRS2000

Delta-doped hybrid advanced detector for low energy particle detection

A delta-doped hybrid advanced detector (HAD) is provided which combines at least four types of technologies to create a detector for energetic particles ranging in energy from hundreds of electron volts (eV) to beyond several million eV. The detector is sensitive to photons from visible light to X-rays. The detector is highly energy-sensitive from approximately 10 keV down to hundreds of eV. The detector operates with milliwatt power dissipation, and allows non-sequential readout of the array, enabling various advanced readout schemes.

Cunningham, Thomas J.↗
NASA NTRS2002

Delta-doped hybrid advanced detector for low energy particle detection

A delta-doped hybrid advanced detector (HAD) is provided which combines at least four types of technologies to create a detector for energetic particles ranging in energy from hundreds of electron volts (eV) to beyond several million eV. The detector is sensitive to photons from visible light to X-rays. The detector is highly energy-sensitive from approximately 10 keV down to hundreds of eV. The detector operates with milliwatt power dissipation, and allows non-sequential readout of the array, enabling various advanced readout schemes.

Cunningham, Thomas J.↗
NASA NTRS1991

Optically induced excitonic electroabsorption in a periodically delta-doped InGaAs/GaAs multiple quantum well structure

Large optically induced Stark shifts have been observed in a periodically delta-doped InGaAs/GaAs multiple quantum well structure. With an excitation intensity of 10 mW/sq cm, an absolute quantum well absorption change of 7000/cm was measured with a corresponding differential absorption change as high as 80 percent. The associated maximum change in the quantum well refractive index is 0.04. This material is promising for device development for all-optical computing and signal processing.

Larsson, A.↗
NASA NTRS2002

Delta-doped CCD's as low-energy particle detectors and imagers

The back surface of a thinned charged-coupled device (CCD) is treated to eliminate the backside potential well that appears in a conventional thinned CCD during backside illumination. The backside of the CCD includes a delta layer of high-concentration dopant confined to less than one monolayer of the crystal semiconductor. The thinned, delta-doped CCD is used to detect very low-energy particles that penetrate less than 1.0 nm into the CCD, including electrons having energies less than 1000 eV and protons having energies less than 10 keV.

Nikzad, Shouleh↗
NASA NTRS2001

Using a delta-doped CCD to determine the energy of a low-energy particle

The back surface of a thinned charged-coupled device (CCD) is treated to eliminate the backside potential well that appears in a conventional thinned CCD during backside illumination. The backside of the CCD includes a delta layer of high-concentration dopant confined to less than one monolayer of the crystal semiconductor. The thinned, delta-doped CCD is used to determine the energy of a very low-energy particle that penetrates less than 1.0 nm into the CCD, such as a proton having energy less than 10 keV.

Nikzad, Shouleh↗
NASA NTRS1995

Growth Of Delta-Doped Layer On Silicon CCD

Response to ultraviolet light enhanced. Back-side-illuminated silicon charge-coupled device fabricated exhibiting nearly 100 percent internal quantum efficiency in near ultraviolet, by using molecular beam epitaxy to grow thin crystalline-silicon layer containing high concentration of boron (p-type dopant). By confining dopant atoms to one or few atomic layers in silicon lattice, concentration-vs.-depth profile made to resemble Dirac delta function, and resulting silicon layer said to be "delta-doped."

Hoenk, Michael E.↗
NASA NTRS2014

Delta-Doping at Wafer Level for High Throughput, High Yield Fabrication of Silicon Imaging Arrays

Systems and methods for producing high quantum efficiency silicon devices. A silicon MBE has a preparation chamber that provides for cleaning silicon surfaces using an oxygen plasma to remove impurities and a gaseous (dry) NH3 + NF3 room temperature oxide removal process that leaves the silicon surface hydrogen terminated. Silicon wafers up to 8 inches in diameter have devices that can be fabricated using the cleaning procedures and MBE processing, including delta doping.

Hoenk, Michael E.↗
DOE OSTI2022

Electric current paths in a Si:P delta-doped device imaged by nitrogen-vacancy diamond magnetic microscopy

The recently-developed ability to control phosphorous-doping of silicon at an atomic level using scanning tunneling microscopy, a technique known as atomic precision advanced manufacturing (APAM), has allowed us to tailor electronic devices with atomic precision, and thus has emerged as a way to explore new possibilities in Si electronics. In these applications, critical questions include where current flow is actually occurring in or near APAM structures as well as whether leakage currents are present. In general, detection and mapping of current flow in APAM structures are valuable diagnostic tools to obtain reliable devices in digital-enhanced applications. In this report, we used nitrogen-vacancy (NV) centers in diamond for wide-field magnetic imaging (with a few-mm field of view and micron-scale resolution) of magnetic fields from surface currents flowing in an APAM test device made of a P delta-doped layer on a Si substrate, a standard APAM witness material. We integrated a diamond having a surface NV ensemble with the device (patterned in two parallel mm-sized ribbons), then mapped the magnetic field from the DC current injected in the APAM device in a home-built NV wide-field microscope. The 2D magnetic field maps were used to reconstruct the surface current densities, allowing us to obtain information on current paths, device failures such as choke points where current flow is impeded, and current leakages outside the APAM-defined P-doped regions. Analysis on the current density reconstructed map showed a projected sensitivity of ~0.03 A m -1 , corresponding to a smallest-detectable current in the 200 μm wide APAM ribbon of ~6 μA. These results demonstrate the failure analysis capability of NV wide-field magnetometry for APAM materials, opening the possibility to investigate other cutting-edge microelectronic devices.

77 NANOSCIENCE AND NANOTECHNOLOGY↗
DOE OSTI2024

High conductivity coherently strained quantum well XHEMT heterostructures on AlN substrates with delta doping

Polarization-induced two-dimensional electron gases (2DEGs) in AlN/GaN/AlN quantum well high-electron-mobility transistors on ultrawide bandgap AlN substrates offer a promising route to advance microwave and power electronics with nitride semiconductors. The electron mobility in thin GaN quantum wells embedded in AlN is limited by high internal electric field and the presence of undesired polarization-induced two-dimensional hole gases (2DHGs). To enhance the electron mobility in such heterostructures on AlN, previous efforts have resorted to thick, relaxed GaN channels with dislocations. In this work, we introduce n-type compensation δ-doping in a coherently strained single-crystal (Xtal) AlN/GaN/AlN heterostructure to counter the 2DHG formation at the GaN/AlN interface, and simultaneously lower the internal electric field in the well. This approach yields a δ-doped XHEMT structure with a high 2DEG density of ∼3.2×1013 cm−2 and a room temperature (RT) mobility of ∼855 cm2/Vs, resulting in the lowest RT sheet resistance 226.7 Ω/□ reported to date in coherently strained AlN/GaN/AlN HEMT heterostructures on the AlN platform.

Physics↗
DOE OSTI2020

Assessing atomically thin delta-doping of silicon using mid-infrared ellipsometry

Hydrogen lithography has been used to template phosphine-based surface chemistry to fabricate atomic-scale devices, a process we abbreviate as atomic precision advanced manufacturing (APAM). In this work, we use mid-infrared variable angle spectroscopic ellipsometry (IR-VASE) to characterize single-nanometer thickness phosphorus dopant layers (δ-layers) in silicon made using APAM compatible processes. A large Drude response is directly attributable to theδ-layer and can be used for nondestructive monitoring of the condition of the APAM layer when integrating additional processing steps. Furthermore, the carrier density and mobility extracted from our room temperature IR-VASE measurements are consistent with cryogenic magneto-transport measurements, showing that APAM δ-layers function at room temperature. Finally, the permittivity extracted from these measurements shows that the doping in the APAM δ-layers is so large that their low-frequency in-plane response is reminiscent of a silicide. However, there is no indication of a plasma resonance, likely due to reduced dimensionality and/or low scattering lifetime.

2D material↗
NASA NTRS1992

Delta-Doped Buried Channels In Charge-Coupled Device

Buried-channel charge-couple devices (CCD's) of proposed new type contain multiple thin, highly-doped channel layers instead of single relatively thick channel layers. Benefits: better performance at low temperature and less sensitivity to damage by radiation.

Fossum, Eric R.↗