Carbon-doped MOCVD InP is semi-insulating up to 700°C

InP:C layers grown by metal organic vapour phase epitaxy at 500°C and doped with CCl(ind 4) remain semi-insulating following anneals up to 700°C. The compensation of grown-in CP acceptors ([CP]about 5×1018cm-3) is attributed to the presence of C-C deep donor defects, revealed by Raman scattering. [CP] and the concentration of grown-in CP-H pairs both decrease with increasing temperatures. CIn, VInH4 or PIn shallow donors are not detected. Reductions in the internal random electric fields upon annealing lead to narrowing of the CP localised vibrational mode. Samples annealed at 800°C become lightly n-type (about 10(exp 16)cm-3).