Joseph L. Schmit

The effect of annealing temperature on the carrier concentration OF Hg0.6Cd0.4Te

The carrier concentration dependence of Hg0.6Cd0.4Te on annealing temperature for the Hg and Te saturation condi-tions is presented in this paper. At low annealing tempera-tures, TA < 350‡ C, residual donor impurities apparently limit the carrier concentration. In contrast, at higher annealing temperatures, 350‡ C < T < 700‡ C, the stoichio-metric acceptor density is increased such that the residual donors are compensated and the material is converted to p-type with an acceptor density as large as 1017 cm−3 . An empirical expression describing this dependence of the acceptors on annealing temperature is given for both the Hg and Te saturation condition: P (Hg saturation) = 1.46 × 1022 exp (−0.84/kTA), P (Te saturation) = 1.90 × 1018 exp (−0.15/kTA).

Doping properties of selected impurities in Hg1−x Cdx Te

The doping properties of selected impurities in Hg1-x Cdx Te have been determined. Primary emphasis is on elements from Groups IB and IIIA, expected to substitute on the metal sublattice, and on elements from Groups VA and VIIA, expected to substitute on the Te sublattice. In addition, the behavior of some elements from Group IV as well as behavior of Li has been determined. Impurities were introduced into Hg1-x Cdx Te either by diffusion or during crystal growth. Cu, Ag and Li are fast diffusing acceptors, Ga is a fast diffusing donor, Al and Si are donors which require high diffusion temperature to effect diffusion, P and As are slowly diffusing acceptors and Br is a slowly diffusing donor. Sn appears to be inactive. In general, impurities substituted on the metal sublattice are rapid diffusers while those substituted on Te sites are slow diffueers.

LPE growth of Hg0.60Cd0.40Te from Te‐rich solution

Hg0.60Cd0.40Te has been grown at atmospheric pressure using a liquid phase epitaxy (LPE) slider system. The compositions are uniform to within ±0.01 mole fraction across the layer and with depth into the layer except for a 3‐μm‐thick interdiffusion region. The layers are p type as grown with carrier concentration of 1017 cm−3 and are annealable to n type with a carrier concentration of 4×1015 cm−3.

Multiwafer growth of CdTe on GaAs by metalorganic chemical vapor deposition in a vertical, high‐speed, rotating disk reactor

Growth of CdTe (111) layers on GaAs (100) and GaAs (111) substrates by metalorganic chemical vapor deposition (MOCVD) has been investigated using a commercial, vertical, high‐speed, rotating disk reactor. Dimethylcadmium (DMCd) and diisopropyltelluride (DIPTe) were used as the growth precursors. The growth rate was measured over the temperature range from 308 to 402 °C. DMCd molar growth efficiencies greater than 50% are obtained for growth temperatures greater than 368 °C. X‐ray rocking curves for the (422) and (333) reflection planes of CdTe (111)<90 arcsec full width at half maximum were obtained at 380 °C for films on the (111) substrates. Scanning electron microscopy on cleaved wafers and infrared interference spectroscopy show edge‐to‐edge thickness uniformity to be 1.3%. The far‐infrared reflectivity was measured using a Fourier transform infrared spectrometer to obtain the TO phonon spectra. These data indicate that the thickness and dielectric constant of the CdTe is extremely uniform. Overall, t...

Infrared excitation spectrum of thallium‐doped silicon

The excitation spectrum of thallium‐doped silicon has been measured in crystals doped to a level of 5×1016 Tl/cm3. The spectrum is characteristic of an effective‐mass‐like acceptor with an optical ionization energy of 0.246 meV. The peak optical cross section was estimated to be 2.6×10−17 cm2.

Anomalous temperature dependence of lattice parameters of metalorganic chemical vapor deposition CdTe grown on GaAs

It is reported that the lattice parameters of a 3‐μm‐thick [1,0,0] single crystal CdTe epitaxial layer on a [1,0,0] single crystal GaAs substrate behave anomalously below 120 K. The epilayer used in this experiment was deposited at 410 °C by metalorganic chemical vapor deposition. This x‐ray lattice parameter study was done in the temperature range between about 8 and 300 K. Our results show that the lattice parameters perpendicular to the surface of both the GaAs substrate and the CdTe epilayer shrink four times more than the corresponding bulks when the samples are cooled down to 10 K. It is further seen that there is no compensation effect between the elements of the composite system; that is, the lattice parameters of the two materials change in the same direction as if the composite system—the epilayer and the thickness of the substrate which is probed by the x rays—would behave as a new material with entirely new physical properties.

X-Ray Diffraction of CdTe Epitaxial Layers on GaAs Substrates as a Function of Temperature

A (0,0,1) epitaxial layer of CdTe on a (0,0,1) GaAs substrate has been studied as a function of temperature by x-ray diffraction. Lattice parameters and integrated intensities of Bragg reflections were measured between 10 K and 360 K using a wavelength of 0.7093 Å (Mo Kα). The lattice parameters were measured parallel and perpendicular to the interface. The changes of the integrated intensities with temperature give information about the thermal vibrations. Average Debye temperatures for the substrate and epilayer are 232±2 K and 142±2 K, respectively. These data are compared with data from CdTe and GaAs single crystals in order to understand how strain is propagated and/or relieved in the composite system.