HgTe-CdTe Superlaltice and HgCdTe Epilayer Device Structures Grown by Photon-Assisted Molecular Beam Epitaxy

We present preliminary results on Se diffusion in liquid-phase epitaxy (LPE)-grown HgCdTe epilayers. The LPE Hg 0.78 Cd 0.22 Te samples were implanted with Se of 2.0 · 10 14 /cm 2 at 100 keV and annealed at 350-450°C in mercury saturated vapor. Secondary ion mass spectrometry (SIMS) profiles were obtained for each sample. From a Gaussian fit, we find that the Se diffusion coefficient D Se is about 1-2 orders of magnitude smaller than that of arsenic. The as-implanted Se distribution is taken into account in case of small diffusion length in Gaussian fitting. The D Se was found to satisfy the Arrhenius relationship D Se ¼ D 0 e ÀE=K B T .

Section: Introductioncontrasting

confidence: 58%

Diffusion of Selenium in Liquid-Phase Epitaxy–Grown Hg0.78Cd0.22Te

Zhao

Golding

Littler

et al. 2007

“…The latter is simpler to implement, faster to solve, and has been shown to give results in close agreement with those of the full Poisson solution. 25 (20) In/ In/2 Din = D°n + D°n + Din + D~n ~i (21) We have implemented both the Poisson and quasineutral models into a process simulator indium diffusion and see good agreement between simulations and experimental data.…”

Section: Resultsmentioning

confidence: 84%

Enhanced diffusion and interdiffusion in HgCdTe from fermi-level effects

Robinson

Berding

Hamilton

et al. 2000

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.

“…[13][14][15][16][17][18] Impurities in CdZnTe substrates can diffuse into HgCdTe deposited on these substrates by liquid phase epitaxy (LPE), metal-organic chemical vapor deposition (MOCVD), or MBE. 14 Impurities diffusing from the CdZnTe substrate can affect carrier concentration, mobility, and minority carrier lifetime in the HgCdTe epilayer.…”

Section: Discussionmentioning

confidence: 99%

“…14 Impurities diffusing from the CdZnTe substrate can affect carrier concentration, mobility, and minority carrier lifetime in the HgCdTe epilayer. 16 The density and size of Te precipitates/ inclusions in CdZnTe has further been demonstrated to impact the electrical transport properties of deposited HgCdTe. 14 It has also been demonstrated that Te precipitate/inclusion-related defects near the growth surface of the (112)B CdZnTe substrate affect MBE-deposited HgCdTe epilayers.…”

Section: Discussionmentioning

confidence: 99%

As-Received CdZnTe Substrate Contamination

Benson

Bubulac

Jaime-Vasquez

et al. 2015

State-of-the-art as-received (112)B CdZnTe substrates were examined for surface impurity contamination, polishing damage, and tellurium precipitates/ inclusions. A maximum surface impurity concentration of Al = 7.5 9 10 14 , Si = 3.7 9 10 13 , Cl = 3.12 9 10 15 , S = 1.7 9 10 14 , P = 7.1 9 10 13 , Fe = 1.0 9 10 13 , Br = 1.9 9 10 12 , and Cu = 4 9 10 12 atoms cm À2 was observed on an asreceived 6 9 6 cm wafer. As-received CdZnTe substrates have scratches and residual polishing grit on the (112)B surface. Polishing scratches are 0.3 nm in depth and 0.1 lm wide. The polishing grit density was observed to vary from wafer-to-wafer from $5 9 10 6 to 2 9 10 8 cm À2 . Te precipitate/inclusion size and density was determined by near-infrared automated microscopy. A Te precipitate/inclusion diameter histogram was obtained for the near-surface (top $140 lm) of a 6 9 6 cm substrate. The average areal Te precipitate/inclusion density was observed to be fairly uniform. However, there was a large density of Te precipitates/inclusions with a diameter significantly greater than the mean. Te precipitate/inclusion density>10 lm diameter = 2.8 9 10 3 cm À3 . The large Te precipitates/inclusions are laterally non-uniformly distributed across the wafer.