Simulation of HgTe/CdTe interdiffusion using fundamental point defect mechanisms

Low temperature thermal treatments of CdHgTe, normally in the presence of mercury vapor, are still used on both bulk samples and single and multi-layer epitaxial layers to modify or control the electrical properties. This paper reviews the recent literature reports in this area and develops the existing model to explain certain features of the p to n conversion process. A brief update on compositional interdiffusion at low temperatures is given which shows significant disagreement within literature values. In addition, the paper will describe and comment on some as yet unexplained results (interdiffusion and electrical behavior) following low temperature treatments in both liquid phase and metalorganic vapor phase epitaxial (LPE and MOVPE) layers.

“…57 Good agreement was obtained with the experimental data from Ref. 55 which conflicts with that of Ref. An analytical form for D was also given by Ref.…”

Section: Compositional Interdiffusionmentioning

confidence: 73%

Low temperature thermal annealing effects in bulk and epitaxial CdxHg1−xTe

Capper¹,

Maxey²,

Jones³

et al. 1999

“…This value is very close to that found for cation vacancy diffusion (1.51 eV), providing further support for a vacancy mechanism for the diffusion. 6 The n/ni dependence indicates that the diffusing species, indium vacancy pairs, are neutral, regardless of the charge state of the cation vacancy. This can be understood by considering the quasi-chemical reaction to form In-V pairs…”

Section: Resultsmentioning

confidence: 99%

“…Key words: Interdiffusion; indium diffusion; Fermi-level effect; LWIR, MWIR, and SWIR HgCdTe; mutispectral infrared detectors; point defects; process simulation nisms underlying the diffusion are still not fully understood. [1][2][3][4][5][6] Moreover, a comprehensive model of the interdiffusion that accounts for variations in temperature, Hg pressure, x value, and Fermi level has not been developed. Recent advances in process modeling codes now make it possible to build a numerical model of interdiffusion that accounts for the above dependencies.…”

mentioning

confidence: 99%

Enhanced diffusion and interdiffusion in HgCdTe from fermi-level effects

Robinson

Berding

Hamilton

et al. 2000

Self Cite

Special Issue Paper 657 FERMI LEVEL ENHANCED INTERDIFFUSIONThe fabrication of all HgCdTe-based infrared detectors involves the formation of one or more heterointerfaces. With the increasing interest in developing detectors in the SWIR as well as the MWIR and LWIR bands, and the desire for multispectral sensitivity, the number and complexity of hetero-interfaces is increasing. Because the performance of these detectors depends critically on the precise placement of the hetero-interfaces, any interdiffusion at these interfaces must be understood and controlled. Although much work has been done in this area, the mechaExcessive dopant or compositional mixing (interdiffusion) during the processing of HgCdTe photodiodes can lead to significant reductions in device performance. With the advent of multi-color and wider bandgap detectors, processes developed for single color LWIR and MWIR devices may not be transferable to the more complex structures. An important factor to account for in processing multicolor and wider gap HgCdTe is the effect of the Fermi level on point defect (PD) concentrations. In general, the density of PDs that have donor states in the band gap will be boosted in the presence of acceptors through the energy gained by the donor state electrons dropping into the vacant acceptor states. The density of PDs that have acceptor states in the band gap will be boosted in the presence of donors through a similar compensation mechanism. This Fermi-level effect is increasingly more important as the band gap is widened. Since almost all diffusion is mediated by either native and/or dopant point defects, and the intrinsic carrier concentration is relatively low at typical processing temperatures, significant broadening of composition and dopant profiles can occur in moderately and heavily doped HgCdTe. In this paper, we illustrate the Fermilevel effect on diffusion with two examples: compositional interdiffusion in multicolor detectors and diffusion of indium in MWIR and SWIR detectors.

“…We notice that there is a difference in the diffusion coefficients we obtained for the LWIR and MWIR samples. We explain this difference using an experimentally determined expression proposed by Holander-Gleixner et al, 20 which relates the cadmium fraction x, material temperature T, and Hg partial pressure to the equilibrium vacancy concentration in HgCdTe. The relationship is expressed as C m x; T; P Hg ð Þ ð Þ ¼ 5:08 Â 10 27 þ 1:1 Â 10 28 x À Á Â 1 P Hg ð Þ exp À 1:29 þ 1:36x À 1:8x 2 þ 1:…”

Section: Results and Analysismentioning

confidence: 99%

Arsenic Diffusion Study in HgCdTe for Low p-Type Doping in Auger-Suppressed Photodiodes

Itsuno

Emelie

Phillips

et al. 2010

Controllable p-type doping at low concentrations is desired for multilayer HgCdTe samples in a P + /p/N + structure due to the promise of suppressing Auger processes, and ultimately reduced dark current for infrared detectors operating at a given temperature. In this study, a series of arsenic implantation and annealing experiments have been conducted to study diffusion at low Hg partial pressure with the goal of achieving effective control over dopant profiles at low concentration. Arsenic dopant profiles were measured by secondary ion mass spectroscopy (SIMS), where diffusion coefficients were extracted with values ranging between 3.35 9 10 À16 cm 2 s À1 and 6 9 10 À14 cm 2 s À1 . Arsenic diffusion coefficients were found to vary strongly with Hg partial pressure and HgCdTe alloy composition, corresponding to variations in Hg vacancy concentration.