Dr. Christopher Buurma Profile

Dr. Christopher Buurma

Scientist at Sivananthan Labs Inc

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Publications (5)

Proceedings Article | 8 March 2019 Presentation

Inductively coupled plasma hydrogenation of LWIR type-II superlattices

Paul Boieriu, Christoph Grein, Christopher Buurma, Jered Feldman, Richard Pimpinella, Anthony Ciani, Alexander Soibel, David Ting

Proceedings Volume 10926, 109260I (2019) https://doi.org/10.1117/12.2514077

KEYWORDS: Long wavelength infrared, Plasma, Superlattices, Photodiodes, Hydrogen, Infrared materials, Infrared radiation, Structural engineering, Mercury cadmium telluride, Photodetectors

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Type-II superlattices (T2SLs) have several fundamental advantages over bulk infrared-sensitive materials due to larger band edge effective masses and the ability to have their band structures engineered to suppress Auger recombination, leading to lowering tunneling currents, longer carrier lifetimes and higher ideal sensitivity. Realizing in practice the potential performance gains relies heavily on reducing the number or efficacy of defects that form Shockley-Read-Hall (SRH) recombination centers, which otherwise limit carrier lifetimes. InAs/GaInSb T2SLs typically have relatively short minority carrier lifetimes in comparison with bulk HgCdTe, which has limited the detectivities of photodetectors based on these T2SLs at both cryogenic and ambient operating temperatures. Studies have shown that InAs/InAsSb T2SLs lattice matched to GaSb substrates are comparable in ideal photodiode performance to InAs/GaInSb ones. Reducing the electrical activity of defects by passivating them with hydrogen is equivalent to lowering their density, and has proven successful in other semiconductor systems. We report here results from Ga-free and Ga-containing T2SLs exposed to inductively-coupled plasmas (ICPs). Our technical approach consisted of characterizing the basic material properties of LWIR InAs/InAsSb T2SL wafers and device performance of LWIR InAs/GaSb T2SL photodiodes that were bulk-passivated with atomic hydrogen, and comparing with unpassivated samples. On average, the in-plane Hall electron mobility increased from 1800 cm2/Vs to 6800 cm²/Vs after hydrogenation. ICP hydrogenation also improved the minority carrier lifetime for each of the explored ICP conditions. Lifetime values increased from an average of 80 ns before hydrogenation to almost 200 ns, a relative increase of over 200%, suggest that some recombination-mediating defects have been at least partially passivated. The Hall mobility improvements were found to be rather stable over the considered short periods of room temperature storage.

Proceedings Article | 21 June 2017 Presentation

Advances in low-cost infrared imaging using II-VI colloidal quantum dots (Conference Presentation)

Richard Pimpinella, Christopher Buurma, Anthony Ciani, Christoph Grein, Philippe Guyot-Sionnest

Proceedings Volume 10177, 1017728 (2017) https://doi.org/10.1117/12.2262189

KEYWORDS: Infrared imaging, Quantum dots, Staring arrays, Infrared radiation, Photodetectors, Mid-IR, Infrared detection, Infrared detectors, Infrared photography, Imaging systems

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Proceedings Article | 26 September 2016 Paper

MWIR imaging with low cost colloidal quantum dot films

Christopher Buurma, Richard Pimpinella, Anthony Ciani, Jered Feldman, Christoph Grein, Philippe Guyot-Sionnest

Proceedings Volume 9933, 993303 (2016) https://doi.org/10.1117/12.2239986

KEYWORDS: Infrared imaging, Mid-IR, Infrared radiation, Sensors, Quantum dots, Staring arrays, Infrared photography, Readout integrated circuits, External quantum efficiency, Photodetectors

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Proceedings Article | 21 May 2014 Paper

Miniaturized imaging spectrometer based on Fabry-Perot MOEMS filters and HgCdTe infrared focal plane arrays

S. Velicu, C. Buurma, J. Bergeson, Tae Sung Kim, J. Kubby, N. Gupta

Proceedings Volume 9100, 91000F (2014) https://doi.org/10.1117/12.2053902

KEYWORDS: Electronic filtering, Reflectivity, Spectroscopy, Semiconducting wafers, Infrared imaging, Infrared radiation, Interfaces, Staring arrays, Long wavelength infrared, Spectral resolution

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Imaging spectrometry can be utilized in the midwave infrared (MWIR) and long wave infrared (LWIR) bands to detect, identify and map complex chemical agents based on their rotational and vibrational emission spectra. Hyperspectral datasets are typically obtained using grating or Fourier transform spectrometers to separate the incoming light into spectral bands. At present, these spectrometers are large, cumbersome, slow and expensive, and their resolution is limited by bulky mechanical components such as mirrors and gratings. As such, low-cost, miniaturized imaging spectrometers are of great interest. Microfabrication of micro-electro-mechanicalsystems (MEMS)-based components opens the door for producing low-cost, reliable optical systems. We present here our work on developing a miniaturized IR imaging spectrometer by coupling a mercury cadmium telluride (HgCdTe)-based infrared focal plane array (FPA) with a MEMS-based Fabry-Perot filter (FPF). The two membranes are fabricated from silicon-oninsulator (SOI) wafers using bulk micromachining technology. The fixed membrane is a standard silicon membrane, fabricated using back etching processes. The movable membrane is implemented as an X-beam structure to improve mechanical stability. The geometries of the distributed Bragg reflector (DBR)-based tunable FPFs are modeled to achieve the desired spectral resolution and wavelength range. Additionally, acceptable fabrication tolerances are determined by modeling the spectral performance of the FPFs as a function of DBR surface roughness and membrane curvature. These fabrication non-idealities are then mitigated by developing an optimized DBR process flow yielding high-performance FPF cavities. Zinc Sulfide (ZnS) and Germanium (Ge) are chosen as the low and the high index materials, respectively, and are deposited using an electron beam process. Simulations are presented showing the impact of these changes and non-idealities in both a device and systems level.

Proceedings Article | 4 February 2013 Paper

High operation temperature of HgCdTe photodiodes by bulk defect passivation

Paul Boieriu, S. Velicu, R. Bommena, C. Buurma, C. Blisset, C. Grein, S. Sivananthan, P. Hagler

Proceedings Volume 8631, 86311J (2013) https://doi.org/10.1117/12.2004708

KEYWORDS: Mercury cadmium telluride, Hydrogen, Long wavelength infrared, Silicon, Diodes, Doping, Photodiodes, Plasmas, Mid-IR, Infrared radiation

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