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.

ADVERTISEMENT RETURN TO ISSUEPREVArticleInvestigating the surface chemistry of Mars Anon.Cite this: Anal. Chem. 1995, 67, 19, 605A–610APublication Date (Print):October 1, 1995Publication History Published online22 September 2008Published inissue 1 October 1995https://doi.org/10.1021/ac00115a002RIGHTS & PERMISSIONSArticle Views109Altmetric-Citations9LEARN ABOUT THESE METRICSArticle Views are the COUNTER-compliant sum of full text article downloads since November 2008 (both PDF and HTML) across all institutions and individuals. These metrics are regularly updated to reflect usage leading up to the last few days.Citations are the number of other articles citing this article, calculated by Crossref and updated daily. Find more information about Crossref citation counts.The Altmetric Attention Score is a quantitative measure of the attention that a research article has received online. Clicking on the donut icon will load a page at altmetric.com with additional details about the score and the social media presence for the given article. Find more information on the Altmetric Attention Score and how the score is calculated. Share Add toView InAdd Full Text with ReferenceAdd Description ExportRISCitationCitation and abstractCitation and referencesMore Options Share onFacebookTwitterWechatLinked InReddit PDF (5 MB) Get e-Alerts Get e-Alerts

Delta-doped CCDs have achieved stable quantum efficiency, at the theoretical limit imposed by reflection from the Si surface in the near UV and visible. In this approach, an epitaxial silicon layer is grown on a fully-processed commercial CCD using molecular beam epitaxy. During the silicon growth on the CCD, 30% of a monolayer of boron atoms are deposited nominally within a single atomic layer, resulting in the effective elimination of the backside potential well. These devices are highly uniform and have exhibited long-term stability. To achieve significantly higher total quantum efficiency, antireflection layers can be directly deposited on the device. This was demonstrated in the 250-400 nm region.

Thin, backside-illuminated CCDs are modified by growing a delta-doped silicon layer on the back surface using molecular beam epitaxy. Delta-doped CCDs exhibit stable and uniform 100% internal quantum efficiency. The process consists of growth of an epitaxial silicon layer on a fully processed commercial CCD die in which 30% of a monolayer of boron atoms are incorporated into the lattice nominally in a single atomic layer. Long term stability was tested and showed no degradation of the device quantum efficiency over sixteen months. Reduction of the reflectivity of the Si surface by deposition of HfO2 on the CCD back surface further increased the QE, with measured QE over 80% in some regions of the spectrum. We discuss these results as well as the delta-doped CCD concept and process.

For future planetary science missions, the authors are developing a series of microinstruments using the techniques of silicon-based micromachining. Conventional instruments such as chemical sensors, charged particle analyzers and mass spectrometers are reduced in size and effective volume to the dimension of cubic centimeters, while maintaining or enhancing performance. Using wafer/wafer bonding techniques, selective chemical etching, thin Film growth, and high resolution lithography, complex three dimensional structures can be assembled. This paper discusses the design, implementation and performance of two new instruments: The Micromachined Bessel Box Auger Electron Spectrometer, and the Mars Soil Chemistry Experiment (MOx).

Delta-doped CCDs, developed at JPL's Microdevices Laboratory, have achieved stable 100% internal quantum efficiency in the visible and near UV regions of the spectrum. In this approach, an epitaxial silicon layer is grown on a fully-processed commercial CCD using molecular beam epitaxy. During the silicon growth on the CCD, 30% of a monolayer of boron atoms are deposited on the surface, followed by a 15 $angstrom silicon layer for surface passivation. The boron is nominally incorporated within a single atomic layer at the back surface of the device, resulting in the effective elimination of the backside potential well. The measured quantum efficiency is in good agreement with the theoretical limit imposed by reflection from the Si surface. Enhancement of the total quantum efficiency in the blue visible and near UV has been demonstrated by depositing antireflection coatings on the delta-doped CCD. Recent results on antireflection coatings and quantum efficiency measurements are discussed.

We have used low-temperature silicon molecular beam epitaxy to grow a δ-doped silicon layer on a fully processed charge-coupled device (CCD). The measured quantum efficiency of the δ-doped backside-thinned EG&G Reticon 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 δ-layer with surface density ∼2×1014 cm−2. 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.

We have used low temperature molecular beam epitaxy to grow p+ silicon on a backside-thinned Reticon 512x5 12 CCD. The techniques for preparing the CCD for the growth and the processing conditions are discussed. A 50 A layer of silicon doped with 3x102 B/cm3 was grown at a substrate temperature of 450C. The ultraviolet quantum efficiency of the modified CCD was significantly higher than that of a CCD with an untreated back surface. Charging the back surface of the modified CCD with a Uv flood did not affect the quantum efficiency indicating that the bands were pinned by the added p+ layer. Gold contamination measured by secondary ion mass spectrometry to have a concentration of 1 x 1 0 18 cm3 near the back surface caused the UV quantum efficiency to be lower than optimum by reducing the minority carrier lifetime. 2.

We present absorption data for 2--4-monolayer InAs/GaAs single quantum wells obtained at 77 K using a polarization-based measurement technique. The spectral contribution of the optical loss features arising from bulk GaAs was minimized using the polarization selectivity of absorption in single quantum wells. Based on polarization properties and the results of an envelope-function calculation, the double structure observed in the spectra is attributed to transitions involving confined heavy holes and both confined and unconfined electron states. No evidence of transitions with the participation of confined light holes was found. Well-width fluctuations deduced from the absorption data are a fraction of one monolayer in our samples. The absorption lines were broadened, indicating interface roughness on a scale comparable to the exciton diameter. A single photoluminescence peak overlapping with the lower-energy portion of the fundamental absorption feature was observed in all the samples at 77 K. Although the absorption line of the undoped two-monolayer sample displayed the least broadening, the photoluminescence was red shifted by approximately 70 meV relative to the absorption feature. Presumably, this behavior indicates long-range diffusion of the excitations. Measurements of the temperature dependence and pump-power dependence of the red shift in this sample support this interpretation.

Three InAs/GaAs single quantum wells of 2, 3, and 4 monolayer thickness were characterized using optical and structural techniques. The results of high-resolution transmission electron (HRTEM) microscopy and optical studies which combine absorption, photoluminescence (PL), photoreflectance and cathodoluminescence are presented. p]Using the polarization modulated absorptance technique we observed two absorption features in our samples at 77 K. On the basis of their polarization properties and comparison with an envelope function calculation, these structures are assigned to transitions between the confined heavy-hole and confined and unconfined electron levels. Photoreflectance spectra of the 3- monolayer sample in 77-300 K range show only the fundamental quantum well transition. The temperature dependence of this transition is approximately linear with a slope of 2.2·10-4 eV/K which is significantly lower than in both constituent materials. p]Comparison to the absorption data reveals that the PL spectra are affected by the carrier diffusion and therefore do not provide direct measure of the exciton density of states. Therefore, photoluminescence results alone do not provide unequivocal information about the fundamental transition energy or the interface quality in quantum wells. p]The HRTEM images indicate that while the interfaces of the 2-monolayer sample are smooth and the well thickness is uniform, the 4-monolayer sample has uneven interfaces and contains domains of 2, 3, and 4 monolayers. In agreement with these observations, absorption features broaden with the increased well width. Scanning cathodoluminescence images of the 2- monolayer sample present no evidence of dislocations, which is consistent with the HRTEM observations.

The strain-induced splitting of the heavy-hole (hh) and light-hole (lh) valence bands for 4-mu-m-thick GaAs/Si is examined on a microscopic scale using linear polarized-cathodoluminescence imaging and spectroscopy. The energies and intensities of the hh- and lh-exciton luminescence are quantitatively analyzed to determine spatial variations in the stress tensor. The results indicate that regions near and far from the microcracks are primarily subject to uniaxial and biaxial tensile stresses, respectively. The transition region where biaxial stress gradually converts to uniaxial stress is analyzed, and reveals a mixing of lh and hh characters in the strain-split bands.

A new approach to the design of a Si-based infrared detector is demonstrated, based on internal photoemission over a Si1−xGex/Si heterojunction barrier. The heterojunction internal photoemission device structure is grown by molecular beam epitaxy (MBE). The detector requires a degenerately doped p+-Si1−xGex layer for strong infrared absorption and photoresponse. Doping concentrations to 1020 cm−3 are achieved using boron from a HBO2 source during MBE growth of the Si1−xGex layers. The photoresponse of this device is tailorable, and most significantly, can be extended into the long-wavelength infrared regime by varying the Ge ratio x in the Si1−xGex layers. Results are obtained with x=0.2, 0.28, 0.3, and 0.4 on patterned Si (100) substrates. Photoresponse at wavelengths ranging from 2 to 10 μm is obtained with quantum efficiencies above ∼1% in these nonoptimized structures.

In this analytical paper, a formalismfor second-harmonic and sum-frequency generation in glass fibers is developed. It considers only the lowest-order nonlinearities in regular, step-index fibers. Plots showing the dependence of index-matching frequencies on the core radius and index difference across the core-cladding interface are given. Estimates are given for the conversion efficiencies due to the nonlinear polarization at the core-cladding interface and the bulk nonlinear polarization proportional to E ∇E, which includes quadrupolar terms. It is concluded that the interface effects would be dominant. Calculations for the longitudinal-electric-field-induced nonlinear polarization proportional to E2 that involve the same mode coupling are also included. The calculated conversion efficiencies are small and cannot explain the recently observed high conversion efficiencies that were obtained under nonindex-matched conditions. A maximum conversion efficiency of around 10−5 is predicted under index-matching conditions.