摘要:

The changes in chemistry and electronic structure of the (110) cleavage surface of Hg0.65Cd0.35Te and properties of the film produced are determined by monitoring with photoemission spectroscopy the growth of thin (10 Å) oxide layers on initially clean surfaces. Oxygen uptake, normally quite slow, is stimulated in this case by operating an ionization gauge in line of sight of the sample during the exposures so as to provide a stream of excited oxygen striking the surface. A complex Te oxide is formed which retains Cd but not Hg. The Cd content appears enhanced at the oxide surface. An explanation for the behavior observed is sought in terms of the species produced by the activating gauge and the chemistry of the alloy surface.

ISSN:0734-2101    

DOI:10.1116/1.572262

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

For the Hg–Cd–Te–O system an approximate three‐dimensional diagram of quaternary phase equilibrium at room temperature has been constructed for the first time, to aid in the study of Hg1−xCdxTe surface oxides. Thermodynamic calculations based on standard Gibbs energies of formation were performed to determine which phases are mutually stable. Stability relationships were checked by reaction experiments in mixtures of bulk reference compounds, using Raman spectroscopy for analysis. Elemental Hg is shown to coexist in equilibrium with all of the oxide and telluride phases. Thus, it is likely to be present whenever oxidation is incomplete. CdTeO3is shown to be stable with respect to the other oxides and tellurides. Several instabilities are indicated, in which an oxide can react with the Hg1–xCdxTe to release elemental Hg or Te, or HgTe.

ISSN:0734-2101    

DOI:10.1116/1.572214

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Low‐temperature chemical vapor deposited (CVD) SiO2has proven to be a very important material for use as a passivation on HgCdTe, principally because it combines a high resistivity and low‐temperature application with excellent interface electronic structure. As previously reported, capacitance measurements show no frequency dispersion, andNSSminima below 1×1010cm−2eV−1have been realized.1We report here on an investigation of the composition and structure of the interface between PHOTOX■SiO2and HgCdTe. Wafers of zone melt HgCdTe, withx=0.3 and coated with PHOTOX■SiO2, were analyzed with simultaneous Auger electron spectroscopy (AES) and Ne ion milling. The surface of the wafer was also studied with AES and surface ellipsometry before the SiO2was deposited. Ellipsometry indicates the presence of a thin film on the HgCdTe due to the surface treatment, with thicknesses which vary between 10 and 20 Å from wafer to wafer. The AES measurements indicate a Te count rate similar to that in bulk HgCdTe, plus significant oxygen signal, indicating the thin film is predominantly Te‐oxide. Sputter‐Auger SiO2on HgCdTe shows an interface region width of ∼50 Å. The dominant signals from this region are Si, O, and Te. The Te line shift indicates that an oxide is not present. We interpret this to indicate that the initial thin Te‐oxide layer has been substatially reduced, leaving an interfacial layer of Si, Te, and O betwen the applied SiO2and HgCdTe. The increase inNSSof interfaces formed on oxide‐free HgCdTe indicate this interface layer is beneficial to device passivation.

ISSN:0734-2101    

DOI:10.1116/1.572215

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

SiO2deposited photochemically at a substrate temperature of 100 °C has been evaluated as a surface passivant on Hg1−xCdxTe  (x=0.30). It has been determined that the electrical properties of the (Hg, Cd)Te–SiO2interface are dependent on the pretreatment given the semiconductor surface prior to the insulator deposition. Formation of a thin native oxide on the (Hg, Cd)Te surface during the pretreatment appears to enhance the resultant (Hg, Cd)Te–SiO2interface properties. A significant spread in the (Hg, Cd)Te–SiO2interface properties is observed, likely owing to the nature of how this native oxide forms and interactions between the native oxide and the SiH4in the photochemical reactor. It is shown through neutron activation analysis that the Hg employed as a photochemical sensitizer is incorporated in the SiO2at a concentration of 1.8 ppm.

ISSN:0734-2101    

DOI:10.1116/1.572216

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The reverse bias dark curent of Hg1−xCdxTe (MCT) photodiodes is often dominated by tunneling across a pinched off surface depletion region. The width of this critical region may be modulated by charge exchange with slow surface states in a passivant insulator. Numerical calculations give the correct order of magnitude for observed 1/ fnoise in ZnS passivated MCT photodiodes.

ISSN:0734-2101    

DOI:10.1116/1.572213

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We report the first polarization dependent Raman scattering study in Hg0.8Cd0.2Te from the (100) and (111) faces. The Raman spectra were recorded in the back scattering geometry at 77 K using several lines of an Ar+laser near resonance with theE1optical gap. The study leads to an unambiguous identification of the HgTe and CdTe‐like transverse optical (TO) and longitudinal optical (LO) phonon features. The HgTe‐like TO and LO phonons occur at 122±1 cm−1and 140±1 cm−1and the CdTe‐like LO phonon occurs at 156±1 cm−1; the CdTe‐like TO–LO splitting was too small to be observable. The presence of a symmetry forbidden HgTe‐like TO phonon from the (100) face indicates the presence of defects or disorder. A defect mode was observed at ∼108 cm−1. In addition, an extremely surface sensitive feature was seen at 132 cm−1and has been tentatively assigned to a coupled LO phonon–intersubband excitation from the natural occurring surface inversion layer. A strong feature observed at 135 cm−1may arise from clustering effects.

ISSN:0734-2101    

DOI:10.1116/1.572207

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We report measurements on the minority carrier lifetime inn‐type andp‐type LPE Hg1−xCdxTe/CdTe withx∼0.2. Forn‐HgCdTe, we have measured lifetimes of 4–7 μs at 77 K for passivated samples. These values are comparable to the results reported for bulk material. Forp‐HgCdTe epilayers with thickness ≤20 μm, the measured lifetime is 15–20 ns at 77 K and is suspected to be limited by surface recombination. With excitation through the CdTe substrate, we have attempted to measure the bulk lifetime; preliminary results are reported.

ISSN:0734-2101    

DOI:10.1116/1.572208

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

For the first time, the dynamic dielectric response of the screening medium within a narrow‐gap semiconductor is properly taken into account in treating electron–hole scattering. The interaction potential is shown to have the strikingly simple formU(q,ω)=V(q)/ε (q,ω=q⋅vh), where V(q) is the bare Coulomb potential,vhis the hole velocity, and ε(q,ω) is the dielectric constant of the medium. The screening medium is assumed to consist of core electrons, lattice ions, free electrons, and free holes. The effects of dynamically treating the slowly responding lattice ions and free holes are discussed in detail. It is shown that previous approximations of employing the static and high frequency limits lead to significant error in the calculated electron–hole scattering mobility.

ISSN:0734-2101    

DOI:10.1116/1.572209

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Optical absorption measurements at the fundamental absorption edge in high purity and stochiometrically dopedp‐type Hg0.7Cd0.3Te show the absorption edge to be significantly influenced by valence band tailing due to native Hg vacancy acceptor defects. The absorption coefficient αefor transitions across the band gap increases as αe=α0 exp k(E−E0); for high purity Hg0.7Cd0.3Te at ambient temperaturesk=148 eV−1, this value decreases tok=105 eV−1at acceptor concentrations of around 2×1016cm−3.

ISSN:0734-2101    

DOI:10.1116/1.572210

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

A low frequency ac measuring‐current technique has been used to investigate the magnetoresistance and Hall effect in Hg1−xMnxTe over a temperature range from 2 to 300 K. The exchange interaction between the Mn++ions and the band carriers causes the energy bands to be significantly modified in the presence of a magnetic field. As a result magnetic boil‐off and magnetic‐field‐enhanced hopping have been observed inp‐type semiconducting samples. These effects produce a large decrease of resistance with increasing magnetic field at low temperatures.

ISSN:0734-2101    

DOI:10.1116/1.572211

出版商:American Vacuum Society    

年代:1983

数据来源: AIP