Thermal stress theory of dislocation reduction in the vertical gradient freeze (VGF) growth of GaAs and InP

Abstract

We have developed the quasi-steady state heat transfer/thermal stress model for dislocation generation in the vertical gradient freeze growth (VGF) of GaAs and InP. Dislocation density contour maps for 2 to 4 inch diameter boules reveal a dramatic reduction in dislocation density for both compounds grown by VGF compared to the standard LEC process. For example, we have determined that for 3 inch diameter undoped GaAs grown by VGF the defect density at the edge of the wafer is reduced by at least a factor of six compared to undoped or even In-alloyed LEC material. The theoretical calculations are in satisfactory agreement with etch-pit density (EPD) data for both compunds. In particular, at a temperature gradient of −5 K/cm the calculated results track the EPD counts in both the 〈100〉 and 〈110〉 directions for 3 inch diameter undoped GaAs grown by the VGF technique.