Experimental Investigation of of the use of Elemental Transmutation for efficient
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Contract Period 8/15/01 – 8/14/04 PowerPoint PPT Presentation


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Experimental Investigation of of the use of Elemental Transmutation for efficient p -type doping in HgCdTe and HgCdTeSe Contract Officer: Dr. W. Clark, Army Research Office. PI’s: T.D. Golding and C.L. Littler, University of North Texas. In collaboration with.

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Contract Period 8/15/01 – 8/14/04

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Contract period 8 15 01 8 14 04

Experimental Investigation of of the use of Elemental Transmutation for efficient p-type doping in

HgCdTe and HgCdTeSe

Contract Officer: Dr. W. Clark, Army Research Office

PI’s: T.D. Golding and C.L. Littler, University of North Texas

In collaboration with

Dr. J.H. Dinan, US Army CECOM NVESD, Fort Belvoir

J.A. Dura, R.M. Lindstrom, NIST, Gaithersburg, MD

H.F. Schaake , DRS Infrared Technologies, Dallas, TX

Contract Period 8/15/01 – 8/14/04


Contract period 8 15 01 8 14 04

Rational

l Control of p-type doping processes in HgCdTe is a prerequisite to fabricate high performance infrared detector devices.

lGroup I elements such as Li, Cu, Ag, and Au are readily incorporated into metallic sites giving p-type activity, their high diffusion coefficients restrict their use in advanced devices.

lGroup V element As is preferred as a p-dopant because it has a low diffusivity.

lHowever, As is amphoteric within the HgCdTe lattice, occupying both metal and nonmetal sites, giving donor and acceptor characteristics respectively.

lRequires complex deposition and annealing schemes to give p-type behavior.


Contract period 8 15 01 8 14 04

Rational (cont.)

  • lTwo techniques are being studied for incorporating As into HgCdTe that should ensure its presence only on nonmetal sites.  

    l Based on the fact that Se can be readily incorporated into group VI sites and that 75Se naturally decays into 75As.  

  • Since the nuclear recoils associated with this decay are too small to displace arsenic atoms, substitutional p-doping should be ensured.  

    l Method (I): Transmutation Doping (TD)

  • Isotopically pure or isotopically enhanced 75Se can be incorporated onto nonmetal sites in HgCdTe at dopant-concentration levels. 75Se subsequently decays to As.

  • l Method (II):Neutron Transmutation Doping (NTD)

  • A HgCdTe74Se quaternary alloy epilayer with low Se content (< 1%) can be exposed to a thermal neutron flux, transmuting the stable 74Se isotope into unstable 75Se via neutron capture. As in Method I, 75Se subsequently decays to As.


Contract period 8 15 01 8 14 04

Progress to date

Magneto-transport measurements

Effects of neutron irradiation on transport properties

Magneto-conductivity tensor analysis of Hall anomalous transport effects (two-electron model)

Future Work

Se incorporation in LPE HgCdTe

Transport and Magneto-Optics


Contract period 8 15 01 8 14 04

“Nominally undoped HgCdTe epilayers will be supplied for this program by the US Army Night Vision Laboratories, and DRS Infrared…”

40 samples of LPE HgCdTe supplied to UNT by DRS: 10 samples of MBE HgCdTe supplied to UNT by NVEOL

”The control samples will be fully characterized at UNT by temperature dependent magnetotransport and magneto-optics to determine carrier levels, mobilties, compensation and defect levels…”

5 of control samples characterized by temperature-dependent magnetotransport. Concentrations, mobilities, and transport mechanisms determined for these samples.

“The HgCdTe alloys will be irradiated in a thermal neutron flux using the reactor facilities at the National Institute for Standards and Technology…”

5 of samples irradiated and characterized by temperature-dependent magnetotransport. Effects of irradiation on the properties of HgCdTe determined.

“The test samples will be characterized by SIMS to determine dopant (Se and As) profiles…”

2 samples implanted with As and Se (2 x 1014 cm-3)

Samples currently at DRS Infrared for activation anneal


Contract period 8 15 01 8 14 04

Experimental Resultsn1 = 1.47 x 1014 cm-3

1 = 7.52 x 104 cm2/V.s

n2 = 1.85 x 1014 cm-3

2 = 2.67 x 104 cm2/V.s

Two Carrier Fit


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