HOLE DEFECTS IN LOW FREE-CARRIER DENSITY GAAS GROWN BY LOW-PRESSURE METALORGANIC VAPOR-PHASE EPITAXY

Unintentionally doped epitaxial GaAs grown by low-pressure metalorganic vapour phase epitaxy has been characterized using both conventional electrical deep-level transient spectroscopy (DLTS) [1] and optical DLTS (ODLTS) [2]. From this study it is shown that the choice of substrate material is important when characterizing material to be used for process-induced defect characterization. Material grown on silicon-doped n+ (10(18) cm-3) GaAs substrate material has an electron defect, a copper defect [3] and two hole traps that have not yet been reported. The three hole traps, presumably introduced by the n+ substrate, compensate the material, causing a reduction in the carrier concentration from 2 x 10(14) cm-3 when the epitaxial layer is grown on semi-insulating (SI) substrate material to 4 x 10(13) cm-3 when grown on n+ (10(18) cm-3) substrate material.