In depth study of the compensation in annealed heavily carbon doped GaAs

摘要

Heavily C-doped GaAs epitaxial layers with holes concentrations ranging from 10~(19) to 1.6 X 10~(20) cm~(-3) have been grown by metal organic vapour phase epitaxy (MOVPE) using CCl_4 as C-growth precursor. The carbon doping characteristics of GaAs epilayers have been investigated by optimizing the Ⅴ/Ⅲ ratio and the growth temperature. Additional informations have been extracted from the evolution of the in situ reflectivity signal during the growth of GaAs:C. The appearance of discernible oscillations in the reflectivity response indicates the high carbon incorporation and the good surface quality in spite of the CCl_4 etching effect. The hole concentration tends to saturate at about 1.5 X 10~(20) cm~(-3). The comparison between Hall effect measurements realized on sets of as grown and annealed layers, and theoretical calculations of the mobility lead to the determination of the compensation ratio of the samples. The lattice matching conditions were systematically investigated by using high X-ray diffraction measurements from (004) and (115) planes. A comparison between the experimental mismatch and the one calculated with the Vegard's law allows the estimation of the possible origin of the compensation. Secondary ion mass spectrometry, scanning electron microscopy and atomic force microscopy have been used as complementary tools to characterize the films.