Todd J. Jones

Delta-doped electron-multiplied CCD with absolute quantum efficiency over 50% in the near to far ultraviolet range for single photon counting applications

We have used molecular beam epitaxy (MBE) based delta-doping technology to demonstrate nearly 100% internal quantum efficiency (QE) on silicon electron-multiplied charge-coupled devices (EMCCDs) for single photon counting detection applications. We used atomic layer deposition (ALD) for antireflection (AR) coatings and achieved atomic-scale control over the interfaces and thin film materials parameters. By combining the precision control of MBE and ALD, we have demonstrated more than 50% external QE in the far and near ultraviolet in megapixel arrays. We have demonstrated that other important device performance parameters such as dark current are unchanged after these processes. In this paper, we briefly review ultraviolet detection, report on these results, and briefly discuss the techniques and processes employed.

Direct detection and imaging of low-energy electrons with delta-doped charge-coupled devices

We report the use of delta-doped charge-coupled devices (CCDs) for direct detection of electrons in the 50–1500 eV energy range. We show that modification of the CCD back surface by molecular beam epitaxy can greatly improve sensitivity to low-energy electrons by introducing an atomically abrupt dopant profile to eliminate the dead layer. Using delta-doped CCDs, we have extended the energy threshold for detection of electrons by over an order of magnitude. We have also measured high gain in response to low-energy electrons using delta-doped CCDs. The effect of multiple electron hole pair production on the observed signals is discussed. Electrons have been directly imaged with a delta-doped CCD in the 250–750 eV range.

Single Photon Counting UV Solar-Blind Detectors Using Silicon and III-Nitride Materials

Ultraviolet (UV) studies in astronomy, cosmology, planetary studies, biological and medical applications often require precision detection of faint objects and in many cases require photon-counting detection. We present an overview of two approaches for achieving photon counting in the UV. The first approach involves UV enhancement of photon-counting silicon detectors, including electron multiplying charge-coupled devices and avalanche photodiodes. The approach used here employs molecular beam epitaxy for delta doping and superlattice doping for surface passivation and high UV quantum efficiency. Additional UV enhancements include antireflection (AR) and solar-blind UV bandpass coatings prepared by atomic layer deposition. Quantum efficiency (QE) measurements show QE > 50% in the 100–300 nm range for detectors with simple AR coatings, and QE ≅ 80% at ~206 nm has been shown when more complex AR coatings are used. The second approach is based on avalanche photodiodes in III-nitride materials with high QE and intrinsic solar blindness.

A system and methodologies for absolute quantum efficiency measurements from the vacuum ultraviolet through the near infrared

In this paper we present our system design and methodology for making absolute quantum efficiency (QE) measurements through the vacuum ultraviolet (VUV) and verify the system with delta-doped silicon CCDs. Delta-doped detectors provide an excellent platform to validate measurements through the VUV due to their enhanced UV response. The requirements for measuring QE through the VUV are more strenuous than measurements in the near UV and necessitate, among other things, the use of a vacuum monochromator, good dewar chamber vacuum to prevent on-chip condensation, and more stringent handling requirements.

Atomically precise surface engineering of silicon CCDs for enhanced UV quantum efficiency

The authors report here on a new technique, combining the atomic precision of molecular beam epitaxy and atomic layer deposition, to fabricate back illuminated silicon CCD detectors that demonstrate world record detector quantum efficiency (>50%) in the near and far ultraviolet (155–300 nm). This report describes in detail the unique surface engineering approaches used and demonstrates the robustness of detector performance that is obtained by achieving atomic level precision at key steps in the fabrication process. The characterization, materials, and devices produced in this effort will be presented along with comparison to other approaches.

Direct Detection of 100–5000 eV Electrons With Delta-Doped Silicon CMOS and Electron-Multiplying CCD Imagers

We have demonstrated a direct detection of 100-5000 eV electrons with a back-illuminated boron delta-doped hybrid silicon complementary metal-oxide-semiconductor imager operating in full depletion and a silicon electron-multiplying charge-coupled device (CCD) operating in partial depletion. The delta-doping molecular beam epitaxy increases sensitivity to low-energy electrons and improves low-energy electron detection threshold relative to conventional solid-state detectors. We compare the gain measured in these two delta-doped devices with gain measured from control delta-doped CCDs.

High-efficiency UV/optical/NIR detectors for large aperture telescopes and UV explorer missions: development of and field observations with delta-doped arrays

Abstract. Exciting concepts are under development for flagship, probe class, explorer class, and suborbital class NASA missions in the ultraviolet/optical spectral range. These missions will depend on high-performance silicon detector arrays being delivered affordably and in high numbers. To that end, we have advanced delta-doping technology to high-throughput and high-yield wafer-scale processing, encompassing a multitude of state-of-the-art silicon-based detector formats and designs. We have embarked on a number of field observations, instrument integrations, and independent evaluations of delta-doped arrays. We present recent data and innovations from JPL’s Advanced Detectors and Systems Program, including two-dimensional doping technology, JPL’s end-to-end postfabrication processing of high-performance UV/optical/NIR arrays and advanced coatings for detectors. While this paper is primarily intended to provide an overview of past work, developments are identified and discussed throughout. Additionally, we present examples of past, in-progress, and planned observations and deployments of delta-doped arrays.

Simultaneous direct detection of sub keV molecular and atomic ions with a delta-doped charge-coupled device at the focal plane of a miniature mass spectrometer

A delta-doped charge-coupled device (CCD) was used for the simultaneous and direct detection of low-energy atomic and molecular ions dispersed along the focal plane of a miniature mass spectrometer (MMS). The measured detection threshold for charged particles with a delta-doped CCD has been extended down to 700eV, representing over an order of magnitude improvement compared to conventional solid-state detectors. We report the direct detection of 700eV energy ions by the mass spectral measurements of species such as iron pentacarbonyl. The combination of delta-doped CCD and MMS enables high-speed, precision mass spectrometry of ions and molecules on a small scale suitable for field and space applications.A delta-doped charge-coupled device (CCD) was used for the simultaneous and direct detection of low-energy atomic and molecular ions dispersed along the focal plane of a miniature mass spectrometer (MMS). The measured detection threshold for charged particles with a delta-doped CCD has been extended down to 700eV, representing over an order of magnitude improvement compared to conventional solid-state detectors. We report the direct detection of 700eV energy ions by the mass spectral measurements of species such as iron pentacarbonyl. The combination of delta-doped CCD and MMS enables high-speed, precision mass spectrometry of ions and molecules on a small scale suitable for field and space applications.

Single-event keV proton detection using a delta-doped charge-coupled device

Using a delta-doped charge-coupled device (CCD), we have demonstrated an order-of-magnitude improvement in the low-energy cutoff for particle detection compared to conventional solid-state detectors. Individual protons with energies in the 1.2–12 keV range were successfully detected using a delta-doped, back-illuminated CCD. Moreover, it is shown that, by measuring the charge generated by the proton, it is potentially possible to use delta-doped CCDs to determine the energy of the incoming particle.

Plasma treatment methods to improve indium bump bonding via indium oxide removal

Flip chip hybridization, also known as bump bonding, is a packaging technique for microelectronic devices which directly connects an active element or a detector to a substrate readout face down, eliminating the need for wire bonding. Indium bump technology has been a part of hybridization for many years and has been extensively employed in the infrared imager industry. However, obtaining a reliable, high yield process for high density patterns of bumps can be quite difficult in part due to the tendency of the indium bumps to oxidize during exposure to air. In this study, plasma, thermal, and wet chemical methods were screened to determine their ability to remove indium oxide from indium bumps. A novel two-step plasma process using methane, argon, and hydrogen was developed that removes indium oxide from indium bumps after prolonged air exposure while maintaining a low sample temperature. This method was tested by fabricating a fully hybridized scientific grade visible complementary metal oxide semiconduc...