Growth of semi-insulating GaAs crystals in low temperature gradients by using the Vapour Pressure Controlled Czochralski Method (VCz)

Abstract

The present paper gives a review on fundamentals, modelling, growth, structural and electrical properties of semi-insulating GaAs single crystals, grown in low temperature gradients by the Vapour Pressure Controlled Czochralski Method (VCz), with diameters from 75 up to 150 mm. Special attention is drawn to the investigation of the temperature-fields inside the growing crystals (and thus thermoelastic stress). Additionally, the influence of convective transport of heat within meit and inert gas is investigated by both experiment and modelling. Thermodynamic aspects of arsenic pressure control within the inner VCz chamber as well as the special experimental and technological challenges are discussed. High quality 100 mm (4-inch) crystals with EPD < 10 4 cm −2 and low as-grown residual strain are presented. Very low carbon concentrations of ≈10 14 cm −3 were obtained for the first time in VCz crystals. This material, as one of the challengers to conventional LEC material, is able to meet similar electrical specifications whilst showing improved structural quality and better parameter homogeneity even in the as-grown state. Initial studies of a VCz crystal grown without boric oxide encapsulant is presented.