Multi-crystal Diffractometry Research Articles

Persistent Photoconductivity under Atmospheric Pressure in Uniformly Doped n-GaAs Prepared by Intermittent Injection of ( CH 3 ) 3Ga / AsH3

The persistent photoconductivity (PPC) of undoped low temperature (LT) grown GaAs has been investigated by temperature-dependent resistance measurements. The PPC phenomenon has been observed under atmospheric pressure in uniformly doped n-GaAs for the first time. It is shown that the recovery temperature is 230 K, and four distinct peaks appear in the PPC spectrum. From the results of secondary ion mass spectroscopy and X-ray multicrystal diffractometry analysis, it is considered that the LT-GaAs layers contain arsenic precipitates or related defects, and that the PPC phenomenon is associated with excess arsenic-related defects in the layers. © 2001 The Electrochemical Society. All rights reserved.

X-ray multi-crystal diffractometry analysis of heavily Te-doped GaAs grown by intermittent injection of TEGa/AsH 3 in ultra high vacuum

This paper reports the results of X-ray multi-crystal diffractometry analysis of heavily Te-doped (1 0 0)-GaAs epitaxial thin layers grown by intermittent injection of TEGa/AsH 3 in an ultra high vacuum. It is shown that the differential lattice strain in 〈1 0 0〉 direction was increased monotonically with increase of impurity concentration in the range of 5×10 19–5×10 20 cm −3, but full-width at half-maximum of rocking curve was kept constant at about 360 s of arc. Independent of the impurity concentration, reflection X-ray topography does not reveal the formation of misfit dislocation. Reciprocal lattice mapping method is also applied to clarify the origin of double peaks in X-ray rocking curve. In addition with electrical measurement results, defect formation mechanism in heavily Te-doped GaAs thin layers are discussed.

Microstructure and lattice distortion of anodized porous silicon layers

The lattice distortion and the microstructure of porous silicon (PS) layers, produced on p-type Si wafers with various electrical resistivities, have been investigated by means of X-ray multi-crystal diffractometry, transmission electron microscopy, infrared spectroscopy and gas adsorption method. It is shown that the lattice distortion of the PS layer is strongly influenced by hydrogen atoms chemisorbed on pore surfaces as well as by pore morphology in the layer, and that the crystalline quality of the layer is degraded secondarily as a result of oxidation on pore surfaces caused after desorption of hydrogen atoms from this layer. A hypothesis is proposed to explain consistently all the experimental results concerning crystalline properties of PS layers.

Growth of nearly perfect alkali halide single crystals by Czochralski method and their characterisation

Nearly perfect single crystals of KCl with diameters in the following ranges were grown on a crystal puller developed in our laboratory: (i) about 10 mm, (ii) 20–25 mm, (iii) 35–40 mm and (iv) 45–55 mm. The rates of pulling were in the range 10 to 20 mm/h, depending upon the diameter. The maximum length of the crystals was about 100 mm. Carefully selected seeds held in air cooled silver plated copper seed holders were used. The rate of rotation was 30 RPM. The temperature of the melt was controlled manually and could be maintained within ±1°C of the desired value. Conditions for growth of nearly perfect KBr crystals of the following diameters were optimised: (i) about 10 mm, (ii) about 20 mm and (iii) about 40 mm. The rates of growth for these crystals were the same as those for the KCl crystals. These crystals were characterised regarding perfection by transmission X-ray diffraction topography and multi-crystal diffractometry (rocking curves). Edge type dislocations having their line vectors along 〈010〉 and 〈210〉 were observed. The half width of the rocking curves of the present crystals was in the range 10–30 s of arc.