Growth and characterization of GaAs crystals produced by the VCz method without boric oxide encapsulation

Thermodynamics, Origin, and Control of Defects

“…There are two effective ways to minimize the precipitation concentration -i) in situ control of the stoichiometric crystal composition, as already described in Section [3.2], and ii) postgrowth annealing under controlled partial pressure. As was demonstrated by Rudolph and Kiessling [46], on applying the VCz growth of GaAs without boric oxide encapsulant, melt compositions less than or around a mole fraction of x L ≈ 0.45 yield near-stoichiometric crystals essentially without precipitation, which is in good agreement with the value predicted by Hurle [10]. Oda et al [36] developed a multiple postgrowth wafer-annealing technology for semi-insulating GaAs.…”

“…EL2 and carbon concentrations of 8.0 × 10 15 and 6.3 × 10 15 cm −3 were obtained, respectively. More information about the intrinsic and extrinsic point defect situation in such crystals with drastically reduced B, O and H contents are given elsewhere [32,45,46]. …”

“…3.3Principle of vapor-pressure-controlled Czochralski (VCz) method without boric oxide encapsulation in order to control the melt composition and, hence, the solid stoichiometry of GaAs crystals by the partial arsenic pressure. The carbon concentration is controlled by flowing CO gas communicating with the inner growth chamber (adapted from Rudolph and Kiessling[46]). …”

TEM investigation of precipitates in VCz GaAs crystals

“…The pulling rates were 3-5 mm h -1 . The decomposition of the melt was controlled in situ via the arsenic partial pressures over their free surface by the arsenic source temperature described in detail elsewhere [8,9]. To determine, which melt compositions the crystals have finally been grown from, the Ga excess of the residual last-to-freeze crucible charge was separated and related to it.…”

“…In order to grow the crystals from constant melt compositions, the encapsulant has to be removed and the arsenic partial pressure over the melt has to be adjusted in situ. For that, the modified vapour-pressure controlled Czochralski (VCz) technique without boron oxide encapsulation has been developed on laboratory scale in a standard high-pressure Czochralski puller LPA Mark 3 at the IKZ in Berlin [8,9]. Using this method, near-stoichiometric crystals without essential precipitation can be grown from melt compositions Ga 1-y As y less or around y ≈ 0.45, with y = N As /(N Ga + N As ) being the mole fraction of the liquid phase, which is in good agreement with the value predicted by Hurle [10].…”