X-ray diffuse scattering identification of interstitial atom aggregates in Si-doped GaAs single crystals

Abstract

Microdefects of different types in highly Si-doped GaAs single crystals grown by the horizontal Bridgman (HB) method were studied by means of X-ray diffuse scattering intensity measurements carried out with the help of a dispersion-free Bragg-type double-crystal spectrometer. It was shown that the predominant microdefects in GaAs crystals, Si-doped to the level of n=3 ×10 18 cm -3, were the so-called interstitial point defect clusters consisting of single interstitials gathered in “clouds” whose mean radius varied from 0.1 to 0.4 μm. A not earlier observed proportionality law I∞( Δθ) -3 is seen on the linearized curve of angular dependence of X-ray diffuse intensity ( I) scattered by the crystal doped to the level determined by the inequality n > 3 × 10 18 cm -3. It was also shown that the angular dependence I ∞ (Δθ) -3 was due to the predominance of extrinsic dislocation loops with mean radius of ∼0.5 μm. Burgers vector determination was based on measuring of the angle corresponding to the X-ray intensity angular dependence transition from I∞( Δθ) -2 to I∞( Δθ) -3, where Δθ is the deviation of the angular position of the second crystal from the accurate Bragg angle.