Characterization of microdefects in GaAs crystals with high-resolution X-ray diffractometry

Abstract

The aim of the present work was to correlate the electric characteristics of Te-doped gallium arsenide grown by LEC technique with the defect contents of the samples. Measurements for GaAs samples, doped with Si, Ge and Ge+Te as well as undoped ones, grown by various methods (HB, VGF and LEC), were also performed. In order to characterize the defects High Resolution X-Ray Diffractometry was used. Measurements of diffuse scattering intensity maps around the reciprocal lattice points and plane wave reflection topography were employed. For most cases in the range of free-electron concentrations between 1-1017 cm 3 and 6.10 TM cm -~ (as well as for SI samples) the isointensity contours in the maps exhibit generally the same character. For higher doping level the intensity of X-ray diffuse scattering increases and it can be further increased by the annealing which causes a decrease of free-electron concentration. Ah analysis of the reciprocal-space maps is presented. Several types of defects should be considered in order to describe isointensity contours. PACS 61.10 -X-ray diffraction and scattering. PACS 61.72. -Defects and impurities in crystals; microstructure. PACS 01.30.Cc -Conference proceedings.

X-ray diffuse scattering characterization of microdefects in highly Te-doped annealed GaAs crystals

“…Measurements of x-ray diffuse scattering (XRDS) close to the Bragg peaks provide information on microdefects, though they do not provide direct images of the defects. Results concerning the effect of thermal annealing of heavily doped GaAs:Te on diffuse x-ray scattering have previously been reported [5]. For the first time a reversible decrease/increase in the electron concentration versus the annealing temperature was found to coincide with a strong increase/decrease in XRDS intensity.…”

High-resolution characterization of microdefects by X-ray diffuse scattering

“…Figure 1a presents a map of sample S1; the characteristic streaks are seen-the vertical sample streak and the skew analyser streak. This image can be treated as a reference map for the perfect crystal as the sample apparently contained only native defects (Zielińska-Rohozińska et al . 1997).…”

“…It is known (Fuller & Wolfstrin 1963;S lupiński et al . 1996;Zielińska-Rohozińska et al . 1997;) that thermal annealing modifies significantly the free-electron concentration of very highly doped n-GaAs.…”

“…Results concerning the effect of thermal annealing of heavily doped GaAs:Te on diffuse X-ray scattering have previously been reported (S lupiński et al . 1996;Zielińska-Rohozińska et al . 1997).…”

Orthorhombic microdefects in Si crystals

“…Before 1997 there were neither experimental proofs of the existence of this type of microdefect in real crystals nor further theoretical considerations. The first x-ray diffuse scattering (XRDS) maps for GaAs crystals containing orthorhombic microdefects were reported in [2]. The most characteristic feature of these maps is the lack of zerointensity lines [3].…”