C. H. Grein

Mercury cadmium telluride/tellurium intergrowths in HgCdTe epilayers grown by molecular-beam epitaxy

Surface crater defects in HgCdTe epilayers grown by molecular-beam epitaxy have been investigated using cross-sectional scanning and transmission electron microscopy, as well as atomic force microscopy. These defects originated primarily within the HgCdTe films, and were shown to be associated with the local development of polycrystalline morphology. High-resolution observations established the occurrence of finely spaced HgCdTe/Te intergrowths with either semicoherent or incoherent grain boundaries, as well as small HgCdTe inclusions embedded within Te grains.

Formation mechanism of crater defects on HgCdTe/CdZnTe (211) B epilayers grown by molecular beam epitaxy

Crater defects on the surfaces of HgCdTe epilayers grown by molecular beam epitaxy have been investigated. A semiempirical model coupled with observations by transmission electron microscopy was used to analyze the defect formation mechanism. We find that Te2 dissociation plays an important role. The defect density can be controlled by adjusting growth conditions such as the substrate growth temperature, Hg flux, growth rate and composition. Tight control over the pretreatment procedures before molecular beam epitaxy growth is also necessary.

Arsenic activation in molecular beam epitaxy grown, in situ doped HgCdTe(211)

Photovoltaic p-n junctions are the most significant active components of both current infrared photodetectors and advanced ones being developed. It is of the utmost importance to control both p- and n-type extrinsic doping. This letter addresses the issue of activating arsenic as a p-type dopant of Hg1−xCdxTe at temperatures sufficiently low that the integrity of p-n junctions and the intrinsic advantages of molecular beam epitaxy as a growth technique will not be compromised. The p-type activation of arsenic in (211)B Hg1−xCdxTe is reported after a two-stage anneal at temperatures below 300 °C for Cd compositions suitable for the sensing of long wavelength infrared radiation.

Effects of hydrogen on majority carrier transport and minority carrier lifetimes in long wavelength infrared HgCdTe on Si

We present the results of using an electron cyclotron resonance (ECR) plasma to incorporate hydrogen into long wavelength infrared HgCdTe layers grown by molecular beam epitaxy. Both as-grown and annealed layers doped in situ with indium were hydrogenated. Secondary ion mass spectroscopy confirmed the incorporation of hydrogen. Hall and photoconductive lifetime measurements were used to assess the effects of the hydrogenation. Increases in the electron mobilities and minority carrier lifetimes were observed for almost all ECR conditions.

Improve molecular beam epitaxy growth of HgCdTe on CdZnTe (211)B substrates using interfacial layers of HgTe∕CdTe superlattices

HgTe∕CdTe superlattices (SLs) have been grown on CdZnTe (211)B substrates as interfacial layers to improve the reproducibility and material properties of epitaxial HgCdTe. The interfacial SL layer is found by transmission electron microscopy to be capable of smoothing out the substrate’s surface roughness and to bend or block threading dislocations from propagating from the substrate into the functional HgCdTe epilayers. The best etch pit density values of 4×104cm−2 were achieved in long-wavelength infrared HgCdTe epilayers with such interfacial layers, while typical values were in the low 105cm−2 range. The recombination mechanisms in such layers were dominated by radiative and Auger intrinsic recombination mechanisms, whereas the contributions from the Shockley-Read-Hall mechanism become negligible, which demonstrated that the use of the SL interfacial layers was beneficial for HgCdTe growth using molecular beam epitaxy or MBE.

Structural and Electronic Properties of Gold Contacts on CdZnTe with Different Surface Finishes for Radiation Detector Applications

State-of-the-art room-temperature, high-resolution x-ray and gamma-ray semiconductor detectors can be fabricated from CdZnTe (CZT) crystals. The structural and electronic properties of the CZT surface, especially the contact interfaces, can have a substantial effect on radiation detector performance, for example leakage current, signal-to-noise ratio, and energy resolution, especially for soft x-rays and large pixilated arrays. Atomically smooth and defect-free surfaces are desirable for high-performance CZT-based detectors; chemo-mechanical polishing (CMP) is typically performed to produce such surfaces. The electrical behavior of the metal/CZT interface varies substantially with surface preparation before contact deposition, and with choice of metal and deposition technique. We report a systematic study of the structural and electronic properties of gold (Au) contacts on CZT prepared with different surface finishes. We observed subsurface damage under Au contacts on CMP-finished CZT and abrupt interfaces for Au on chemically-polished (CP) CZT. Schottky barrier formation was observed for Au contacts, irrespective of surface finish, and less charge trapping and low surface resistance were observed for CP-finished surfaces. Pre-deposition surface treatment produced interfaces free from oxide layers.

Electronic structure of Te- and As-covered Si(211)

Electronic and atomic structures of the clean and As- and Te-covered Si(211) surface are studied using pseudopotential density-functional method. The clean surface is found to have

MBE HgCdTe for HDVIP Devices: Horizontal Integration in the US HgCdTe FPA Industry

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MWIR InAs 1-x Sb x nCBn detectors data and analysis

and rebonded

Pronounced Auger suppression in long wavelength HgCdTe devices grown by molecular beam epitaxy

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