Type-II InAs/GaSb superlattice photodiodes for mid-IR (3-5μm) region grown by solid-source
molecular beam epitaxy are reported. Different approaches for realization of high quality interfaces
between compositionally abrupt GaSb and InAs layers during the growth of the SLs are discussed.
Mid wave infrared (&lgr;c~ 4.5 µm at T=300K) P-on-N designs of SLs detectors were developed to
ensure compatibility with most present day readout integrated circuits (ROICs). Variable size diode
arrays were fabricated using standard photolithography technique and hybridized to silicon fanout
chip. The sizes of the detector mesas were varied from 29μm x 29μm to 804μm x 804μm. The
single pixel characterization was undertaken at Santa Barbara Focal Plane. Temperature-dependent
IV measurements revealed dark current density below 1 x 10-8 A/cm2 at 82K and below 2 x 10-5
A/cm2 at 240K. (Vbias = 0V). Dynamic resistance-area product at zero bias was found to be ~ 1 x 105
Ωcm2 at 82K and 0.24 Ωcm2 at 240K. Influence of protective silicon nitride coating on reduction
surface leakage currents of detectors was investigated. We found that rsurface was equal to ~ 3 x 106
Ωcm indicating the proper surface preparation followed by room temperature Si3N4 deposition is
effective in reduction of leakage currents in type-II MWIR InAs/GaSb superlattice photodiodes.
As the demand for mid wavelength infrared (MWIR) focal plane arrays (FPAs) continues to increase, the quality of InSb
surfaces becomes more stringent. State-of-the art InSb contains <20 etch pits/cm2 (EPD), and provides a surface suitable
for rapid oxide desorption and high quality MBE growth. In order to satisfy resolution and sensitivity requirements for
advanced MWIR FPA imaging systems ( 1 to 5.4 μm region @77°K), the surface and sub-surface of the material must
be of excellent quality. CMP has proven to be a qualified finishing process for InSb surfaces in the fabrication of
IRFPAs. However, a time consuming surface etch is universally required in the IRFPA manufacturing process. Gas
cluster ion beam processing (GCIB) has been shown to significantly enhance the surface oxide desorption of both GaSb
and InSb substrates for MBE growth and provides an alternate surface finish for IRFPA manufacturing. The use of GCIB
may preclude the need for surface etching, thus reducing IRFPA processing time and chemical cleanup. This study
examines the comparison of CMP and GCIB finishes on InSb surfaces and the effect on final IRFPA device pass rates.
NF3/O2 dual energy GCIB surface processing was used in this study. Atomic force microscopy (AFM), cross-section
transmission electron microscopy (XTEM), and rocking curve x-ray diffraction (XRD) examine the surface and subsurface InSb integrity. A comparison of pass-rates for completed IRFPAs with the CMP and GCIB surface shows the pass-rate to be the same, opening the possibility for etch step elimination.
Davis Lange, Paul Vu, Samuel Wang, Steven Jost, Michael Winn, John Roussis, Robert Cook, Darrel Endres, Gregg Dudoff, Colin Jones, Glenn Kincaid, Jeffery Heath
This paper discusses the design, architecture, and performance of a 6000 element Indium Antimonide Infrared focal plane array. The focal plane array architecture allows for any N x 1000 element sized array to be constructed from its base elements. A uniquely constructed bi-staggered detector geometry is utilized to provide 2:1 over-sampling having 10 micron effective pitch in both the across track and along track directions. Additionally, the detector geometry allows for physical pixel sizes up to 25 microns while sampling at a 10 micron effective pitch to provide alias free imaging with the high signal capture capability of a large pixel. The Indium Antimonide detectors are front-side illuminated P-on-N type mesa diodes having no measurable crosstalk. A complimentary CMOS based Multiplexor in a M x 250 segmented design having up to 10 million electrons full-well output with greater than 14 bits instantaneous dynamic range provides a flexible and low noise readout for the focal plane array. Hybridization of the Indium Antimonide detectors and multiplexor is provided via a Lockheed Martin patented beam-lead technology to provide reliable and producible long linear focal plane arrays for reconnaissance applications. Characterization of the 6000 element Infrared focal plane array is presented including dynamic impedance of the diodes, read-noise, linearity, and non-uniformity. Meadured characteristics of the CMOS multiplexor are also presented in addition to data from the hybridized modules making up the Focal Plane Array.
Access to the requested content is limited to institutions that have purchased or subscribe to SPIE eBooks.
You are receiving this notice because your organization may not have SPIE eBooks access.*
*Shibboleth/Open Athens users─please
sign in
to access your institution's subscriptions.
To obtain this item, you may purchase the complete book in print or electronic format on
SPIE.org.
INSTITUTIONAL Select your institution to access the SPIE Digital Library.
PERSONAL Sign in with your SPIE account to access your personal subscriptions or to use specific features such as save to my library, sign up for alerts, save searches, etc.