Evaluation of Surface Cleaning of Si(211) for Molecular-Beam Epitaxy Deposition of Infrared Detectors

Abstract

We report an assessment of the reproducibility of the HF cleaning process and As passivation prior to the nucleation of ZnTe on the Si(211) surface using temperature desorption spectroscopy, ion scattering spectroscopy, and electron spectroscopy. Observations suggest full H coverage of the Si(211) surface with mostly monohydride and small amounts of dihydride states, and that F is uniformly distributed across the top layer as a physisorbed species. Variations in major contaminants are observed across the Si surface and at the CdTeZnTe/Si interface. Defects act as getters for impurities present on the Si surface, and some are buried under the CdTe/ZnTe heterostructure. Overall, the data show evidence of localized concentration of major impurities around defects, supporting the hypothesis of a physical model explaining the electrical activation of defects in long-wave infrared (LWIR) HgCdTe/CdTe/Si devices.

The Distribution Tail of LWIR HgCdTe-on-Si FPAs: a Hypothetical Physical Mechanism

“…Other types of discrete species with various chemical compositions near the ZnTe/Si interface have been observed by the SAM technique. 8 We note that the density of discrete species in the ZnTe/Si interfacial region is in closer agreement with the density of failed pixels than is the EPD of the HgCdTe epilayer.…”

“…The existence of discrete species and their location near the ZnTe/Si interface were confirmed by scanning Auger microscopy (SAM) measurements. 8 Additional information on the discrete species was obtained using a combination of SIMS depth profiling 9 and SIMS imaging. 10 Because of SIMS imaging's low sensitivity, a very high ion count (>10 19 cm À3 ) from the respective element is required.…”

“…The SAM technique detected other impurities in the CdTe/Si interfacial region, such as F, S, and Cu as discussed in Ref. 8. The nucleation layer, nominally ZnTe, plays a key role in converting the threading dislocations into activated threading dislocations (killer dislocations).…”

Microstructural Characterization of CdTe(211)B/ZnTe/Si(211) Heterostructures Grown by Molecular Beam Epitaxy

“…However, further reduction in dislocation density, by at least an order of magnitude, is still needed for high-performance longwavelength infrared (LWIR) HgCdTe FPAs. 16 The initiation of ZnTe growth and the microstructure of the CdTe(211)B/ZnTe/Si(211) heterointerfacial region are important factors that impact the final material quality. Thus, improved understanding of ZnTe nucleation, and better knowledge of the interface structure, should help to facilitate growth of higher-quality epitaxial CdTe and HgCdTe for large-format LWIR FPAs.…”

Effect of As Passivation on Vapor-Phase Epitaxial Growth of Ge on (211)Si as a Buffer Layer for CdTe Epitaxy

“…The modified RCA cleaning procedure of the Si substrate followed in the study, with HF treatment as the last step, creates a H-terminated surface. [12][13][14] However, in a typical CVD reactor with multiple reactant sources, a critical issue is cross-contamination of the starting substrate during heat up with residual reactants present inside the reactor, as a consequence of the ''memory effect.'' The reactor used in the present study had precursors of the following elemental species: Ge, Cd, Te, As, and Zn.…”