Low-temperature annealing of (Hg,Cd)Te

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Exposure to specific damage introduced by either ion implantation or ion milling converts p-type short wavelength infrared (SWIR) HgCdTe to n-type in a manner similar to the conversions in medium wavelength infrared (MWIR) or long wavelength infrared (LWIR) mercury cadmium telluride. However, the depth of conversion for SWIR Hg 1-x Cd x Te, with x 5 0.48, is approximately 300% smaller when compared to the depth of conversion for MWIR HgCdTe for an identical degree of ion milling. The depth of conversion, or the n/p junction depth, tracks linearly the extent of surface removals by ion milling when the metal vacancy concentration is held invariant. These results can be correlated to the interaction between metal vacancies and a product of the lattice damage process resulting from ion milling. The observation of a linear dependence of this depth on the degree or time of ion milling rules out the existence of a diffusive barrier in the transfer of this product for both MWIR and SWIR HgCdTe.

Section: Resultsmentioning

confidence: 97%

Section: Resultsmentioning

confidence: 99%

See 1 more Smart Citation

p to n conversion in SWIR mercury cadmium telluride with ion milling

Chandra¹,

Schaake²,

Aqariden³

et al. 2006

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“…16,17 A combination of all four mechanisms is likely with the sample history determining the dominant factor. Since no cap was grown on these samples, the cap/base interface can be ruled out as a contributor.…”

Section: Discussionmentioning

confidence: 99%

Effect of Dislocations on VLWIR HgCdTe Photodiodes

Parodos

Fitzgerald

Caster

et al. 2007

The effects of dislocations on very-long-wavelength infrared (VLWIR) HgCdTe photodiodes (cutoff wavelength >14 lm at 40 K) have been determined experimentally and analyzed. The photodiodes are in the back-illuminated configuration, fabricated from HgCdTe p-on-n double-layer heterostructure (DLHJ) films grown at BAE Systems by liquid phase epitaxy (LPE) onto lattice-matched (111) CdZnTe substrates. Arrays were hybridized to silicon ROICs to form focal plane arrays (FPAs). After characterization for dark current and response, the arrays were dehybridized and stripped of their metals and passivation layers. Dislocations were revealed using a Hä hnert and Schenk (H&S) etch. Pixel traceability was maintained throughout the analysis, permitting one-to-one correlation between photodiode performance and dislocation density measured within that photodiode. We found that response and dark current were correlated to etch pit density (EPD), which we assumed to be equal to dislocation density. Our results support earlier dislocation studies on larger-bandgap HgCdTe, which showed response was only weakly impacted by EPD, while dark current was strongly affected by EPD. Measured EPD values ranged from low 10 5 to low 10 7 cm -2 . Potential causes for this range in EPD are discussed.

“…The junctions were detected following defect etching of cleaved cross-sections of the films, employing a method developed earlier. 5 In that study, it was demonstrated that the defect etch boundary precisely coincided with the electrical n-p junction.…”

Section: Introductionmentioning

confidence: 88%

Junction Stability in Ion-Implanted Mercury Cadmium Telluride

Chandra

Schaake

Kinch

2008

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Ion implantation into HgCdTe results in the production of Hg interstitials, which can be subsequently driven into the HgCdTe by an annealing process. This diffusive drive-in of the Hg interstitials fills vacancies and kicks out group I impurities and results in the formation of an n-p junction. In this work we report on the production of interstitials during baking subsequent to the ion implantation process. Various concentrations of metal vacancies were first introduced into mid-wavelength infrared (MWIR, 3 lm to 5 lm) HgCdTe by annealing under tellurium-saturated conditions at various temperatures. Baking subsequent to planar implantation of boron produced n-p junctions whose depths were measured by defect etching. The results were modeled using a simple diffusion limited model from a fixed surface concentration. The surface concentration was allowed to decrease exponentially to zero after a time, found to be of the order of $80 h to 150 h. Exhaustion of the interstitials sources produced by the implantation was nearly complete after $400 h. The total number of mercury interstitials produced was approximately 50% of the implant dosage.