摘要:

We report the epitaxial growth of single and double layers of Hg1−xCdxTe on 2×3 cm single‐crystal CdTe substrates, using liquid phase epitaxy (LPE) from tellurium solution in an atmospheric pressure horizontal slider apparatus. The layers are found to be extremely uniform in composition (x) across individual layer areas and in layer‐to‐layer reproducibility (standard deviation 0.002). We report our observations of the morphological, compositional and crystalline quality of the layers, and measurements of the electrical parameters of the layers.

ISSN:0734-2101    

DOI:10.1116/1.572277

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

A preliminary study has been carried out on the electrical properties and chemical purity of epitaxial layers of cadmium mercury telluride (CMT) grown by metal‐organic vapor phase epitaxy (MOVPE). It has been shown that the mobility of such layers grown at 410 °C are comparable with bulk CMT of equivalent carrier concentration. SIMS profile studies of trace impurities in the epitaxial layers and CdTe substrates used for epitaxial deposition revealed significant impurity concentration enhancement (ICE effect) for a number of elements (Li, Na, K, Al, Ga, In and Mn) at the CdTe/CMT interface: some of these elements (Li, Na, K, Al and In) also showed this ice effect at the subsequent CMT/CdTe interface. The magnitude of the ICE effect could be quite large (a factor of ∼ 100 for Li) but its origin was not identified although potential mechanisms for its formation are discussed.

ISSN:0734-2101    

DOI:10.1116/1.572278

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The thermal diffusivity of Hg1−xCdxTe melts is found to rise rapidly with temperature to values characteristic of metals. Solid and melt diffusivities for values ofxfrom 0 to 0.3 and over a temperature range from 150 to 900 °C have been determined by the laser flash method of Parker, Taylor, and Cowan. The diffusivity decreases from a maximum atx=0 in both the solid and the liquid, with the values observed atx=0.3 being about 40% of those forx=0. The solid diffusivity forx=0 is 1.7 mm2/s at 150 °C, decreasing to 0.7 mm2/s at the melting point. Thex=0 liquid diffusivity increases from 0.7 mm2/s at the melting point to 3.5 mm2/s at 900 °C.

ISSN:0734-2101    

DOI:10.1116/1.572241

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Negative thermal expansion has been established in liquid Hg1−xCdxforx<0.2 employing a pycnometric method. Pure HgTe increases in density from its melting point at 670 °C to a maximum value at ∼750 °C, where normal thermal expansion progressively resumes. The dependence of density on temperature for liquid Hg1−xCdxTe arises almost exclusively from the HgTe portion of the melt, while CdTe acts as a diluent. The temperature corresponding to the maximum density changes slightly with composition, increasing by about 5 °C forx=0.1.

ISSN:0734-2101    

DOI:10.1116/1.572242

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Brief summaries of the precipitation of tellurium in (Hg,Cd)Te during the quench from the recrystallization anneal of the solid state recrystallization process and the subsequent dissolution of these precipitates during the postanneal are given. It is shown that if vacancies and interstitials are considered to be the only important point defects in the lattice, the observed mechanisms of precipitation and annihilation require that tellurium in excess of stoichiometry must be accommodated by metal vacancies. Diffusion from the mercury ambient during postanneal then must occur by metal interstitials. Enhanced self‐diffusion on the metal sublattice is shown to occur along grain and subgrain boundaries. The most significant source of dark current in CID imagers fabricated on (Hg,Cd)Te is shown to be a sufficiently high dislocation density in a pixel.

ISSN:0734-2101    

DOI:10.1116/1.572243

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

We have studied a few native defects in Hg1−xCdxTe in the effective mass approximation. For the case of mercury vacancy, which is of particular interest, this approach is quantatatively meaningful. The calculated levels for the neutrals and charged vacancies are reported.

ISSN:0734-2101    

DOI:10.1116/1.572244

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

DLTS and associated electrical measurements were made on unintentionally doped CdTe crystals obtained from several vendors, on Cu‐doped CdTe, and on Te‐annealed CdTe. All of the crystals werep‐type. Four majority carrier deep levels were observed in the temperature range from 100–300 K with activation energies relative to the valence band of 0.2, 0.41, 0.45, and 0.65 eV. Two of these levels were specific to certain crystals while the other two were seen in every sample and are attributed to common impurities or native defects. Fluctuations in the concentrations of levels across samples and as a result of modest sample heating (400 K) were also observed.

ISSN:0734-2101    

DOI:10.1116/1.572245

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Gold is a fast‐diffusing acceptor in HgCdTe. It has been used as ap‐type dopant and as a metal contact. This paper reports the presence of deep levels in gold‐dopedx=0.48 Hg1−xCdxTe. Two types of spectra were observed; each had energy levels betweenEv+1/4EgapandEv+1/2Egap. The capture cross sections for these centers have been determined and for most of the levels they involve small hole capture cross sections, 10−17to 10−21cm2, and moderate electron capture cross sections, 10−15to 10−16cm2. The hole capture cross sections for these centers had large negative activation energies indicative of hole capture at a positive center with a Coulomb repulsive barrier. The corresponding electron capture is then at Coulombically attractive positive centers. The situation described requires that the DLTS activation energies be corrected for the temperature dependence of the hole capture cross sections and for the Poole–Frenkel effect for electron capture. The energy levels and capture cross sections reported make these centers effective minority carrier recombination sites inp‐type material. The minority carrier lifetimes measured are very close to those calculated for Shockley–Read recombination at the DLTS characterized centers.

ISSN:0734-2101    

DOI:10.1116/1.572246

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

The diffusion behavior of mercury in Hg0.8Cd0.2Te was investigated using radiotracer techniques. Complex concentration versus distance profiles resulted from both the gold and mercury diffusion anneals. At 225 °C, complementary error function curve fits to the surface and tail components of the mercury diffusion profile yielded diffusion coefficients of ≂8×10−14and ≂2.5×10−11cm2s−1for the surface and tail regions, respectively. Mercury diffusion coefficients were similar for as‐grown and mercury preannealed samples. Surface concentrations were unknown for the gold diffusion profiles and accurate diffusion coefficient calculations were not made, but the migration rate of gold appeared faster than mercury in Hg0.8Cd0.2Te. A mechanism was proposed for depletion of gold in the near‐surface region of the HgCdTe for long diffusion times in a mercury ambient, which involved the formation of Au/Hg compounds at the slice surface.

ISSN:0734-2101    

DOI:10.1116/1.572247

出版商:American Vacuum Society    

年代:1983

数据来源: AIP

摘要:

Commercially available portable image x‐ray intensifiers have found their usefulness with all existing x‐ray topographic techniques. Real‐time x‐ray topography can be employed to align the diffraction images rapidly before recording them on high resolution film. As a quality control procedure, real‐time Berg–Barrett x‐ray topography can be used to assess macrostructural quality of HgCdTe with approximately 100 μm spatial resolution. As a x‐ray screening technique prepared samples of HgCdTe can be assessed in real time before undergoing unnecessary costly processing on poor material. The advantages and disadvantages of the three basic types of x‐ray topographic system will be discussed. The usefulness of real‐time x‐ray intensification as a support tool to Berg–Barrett, Lang, and ACT topography techniques is evaluated. Also, instrument characteristics of the x‐ray intensifiers which are useful in real‐time x‐ray topography applications will be presented.

ISSN:0734-2101    

DOI:10.1116/1.572250

出版商:American Vacuum Society    

年代:1983

数据来源: AIP