Bulk growth of GaP by halogen vapor transport

Abstract

A conventional vapor transport system for epitaxial growth of GaP on GaAs was modified to permit cooling of the substrate. As a result of this modification crystals of more than 6 mm thickness have been grown. A number of etchants reveal etch grooves on (111) and (110) faces of halogen transported GaP. In such material both microtwin lamellae and stacking faults have been identified by electron microscopy. It was shown that the density of the etch grooves depends on the surface preparation and that it decreases exponentially with increasing distance from the substrate. Macroscopic defects containing excess dopant have been associated with deep pits visible on the growth face. It is suggested that the excess dopant is incorporated by a facet effect. Diodes having external quantum efficiencies as high as 1.5 pct were made by depositing zinc- and oxygen-doped layers by liquid epitaxy directly on tellurium-doped halogen grown GaP. However, the external quantum efficiencies decreased by a factor of 100 when material grown next to the GaAs substrate was used. It was shown that the decrease in the efficiency was not due to high stacking fault densities. Evidence is submitted that the arsenic content of the first to grow layers is deleterious to diode efficiencies.