Influence of Structural Defects on the Mechanical Stress in the Impurity Diffusion Zone of GaAs Single Crystals

Abstract

Data are presented on the mechanical stress σ developing in the diffusion zone of gallium arsenide single crystals at different dislocation densities and relationships between the concentrations of arsenic and gallium vacancies. The results are analyzed in terms of impurity diffusion through gallium, arsenic, and interstitial sites. The influence of the defect system on σ is shown to depend on the mechanism of impurity diffusion. A correction coefficient which eliminates the discrepancy between experimental stress data and theoretical predictions is determined for different diffusion mechanisms.

Change of parameters of semiinsulated undoped GaAs nonstoichiometric crystals under annealing

“…Negative values of σ in initial crystals of group I are caused by the predominance of nonassociated vacancy defects over interstitial ones, whereas positive values of σ in crystals of group II are related to the predominance of nonassociated interstitial defects over vacancy ones [5,6]. The well-known results of radiographic and metallographic investigations of the influence of various HT conditions on the formation of microdefects (MD) in undoped GaAs single crystals [1] allow one to explain the character of the dependences σ = f (t) obtained in this work in the following way.…”

“…These samples were cut from Czochralski-grown SIU GaAs (100) single crystals with the n-type of conductivity. In such crystals, it is possible to estimate the concentration of vacancies and interstitial defects (gallium vacancies [V Ga ], arsenic vacancies [V As ], and interstitial arsenic [As i ]) using photoluminescence (PL) spectra and data on mechanical stresses σ, respectively [4,5].…”

“…At the initial stage of experiments (before HT), the samples had the n-type of conductivity, specific resistance ρ = 7⋅10 7 -2⋅10 8 Ohm⋅cm, and the density of dislocations Ν d = 3⋅10 4 -6⋅10 5 cm -2 . All samples were separated in two groups: group I included the crystals obtained with gallium surplus, where dominating point defects are arsenic vacancies and the lattice constant is smaller than that in stoichiometric crystals; group II included the crystals obtained with arsenic surplus, where dominating point defects are interstitial arsenic atoms and the lattice constant is greater than that in stoichiometric crystals [5][6][7].…”

“…The presence of vacancy defects leads to a decrease in α, which corresponds to compression stresses (negative). Accordingly, the increase or decrease in mechanical stresses σ reflects the increase of the interstitial or vacancy IPD concentration and gives us a possibility to make conclusion about a change of the defect structure of crystals after HT [5]. Therefore, first of all, we will carry out the analysis of the change in σ in both groups of samples.…”

“…Abrupt cooling of samples leads to the IPD "freezing", and the IPD concentration in a crystal at Т = 300 K approaches the equilibrium one at the HT temperature. A surplus atomic component is present in initial crystals of both groups [5,6]. For the crystals of group I, it is gallium.…”