The optical and electronic characteristics of devices based on GaAs (LEDS, laser diodes, etc.) are adversely affected by the dislocations originating in the substrates. We demonstrate by means of thermoelastic analysis that the primary cause for the observed dislocation density patterns in Czochralski‐pulled GaAs single crystals, which serve as a source for substrates, is crystallographic glide, induced by the excessive thermal stresses arising during the growth process. First, we formulate a tractable model for crystal growth. We obtain the temperature distribution in the crystal by solving the quasi‐steady‐state partial differential equation for heat conduction subject to appropriate boundary conditions. The closed‐form solution includes time, pull rate, axial location, radius, convective and radiative heat transfer coefficients (hr + hc), and a fixed ambient temperature (Tα) among the variables. Next, from the temperature profiles we determine the radial, tangential, and axial stress components acting on the GaAs boule. These stresses permit the evaluation of the 12 resolved shear stress components for the {111}, <110> slip system. We postulate the sum of the absolute values of the 12 components (σtot) to be proportional to the dislocation density within an additive constant. Employing σtot as a parameter, we have constructed dislocation distribution contour maps for {100} GaAs wafers which are in good accord with the dislocation patterns observed on KOH‐etched wafers cut from near the top end of Cr and Te‐doped GaAs boules. A detailed examination of the effect of the numerous parameters on the dislocation density of Czochralski‐pulled GaAs is also given. Only by a drastic increase of Tα and a substantial decrease of hr + hc would one be able to overcome the natural limitations imposed by the thermal and mechanical properties on dislocation density. Finally, we pay attention to the effects of elastic anisotropy and interfacial heat flux, discuss the philosophical and mathematical difficulties associated with finding a true transient solution, and provide some practical suggestions.

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The Ga concentration in normalGaP crystals prepared by a variety of techniques (pulled by the liquid encapsulation Czochralski technique from stoichiometric or nonstoichiometric melts, solution grown, and annealed) has been determined by precision coulometric titration, yielding the experimental solidus boundary which exhibits an excess of Ga along the Ga‐rich liquidus. Based on a thermodynamic model, assuming that neutral Ga and P vacancies are the predominant native defects, the analysis of the solidus data permitted the evaluation of the vacancy concentrations over a wide temperature range. At the melting point of normalGaP (1465°C) there are 8 × 1018 and 1.3 × 1019 cm−3 Ga and P vacancies, respectively, in the crystal. The calculated solidus curve well represents the totality of experimental data and shows retrograde temperatures at 1375° and 1400°C on the Ga‐ and P‐rich sides, respectively. The enthalpies and entropies associated with vacancy formation are given and discussed. It is shown that the data provide strong additional support to the previous identification of Ga vacancies with killer centers in normalGaP .

The solid solubility isotherms for Zn in normalGaP and normalGaAs have been calculated as a function of Zn concentration along the Ga‐P‐Zn and Ga‐As‐Zn liquidus isotherms over a wide temperature range. These calculations were based on a critical evaluation of the available solubility data, assuming regular ternary solution behavior in both ternary melts. The solubility isotherms are not only in agreement with the published data, but are also in accord with recent experimental results on the incorporation of Zn in normalGaP grown by liquid‐phase epitaxy and liquid encapsulation pulling. In addition, the Zn surface concentrations in normalGaP and normalGaAs arising from ternary source diffusion have been estimated as a function of temperature. Finally, the enthalpies for the incorporation of Zn in normalGaP and normalGaAs according to normalZnfalse(normallfalse)+VnormalGa=ZnnormalGa are given as approximately −2.16 and −2.29 eV, respectively.