DISLOCATION PROFILES IN HGCDTE(100) ON GAAS(100) GROWN BY METALORGANIC CHEMICAL-VAPOR-DEPOSITION

We studied dislocation etch pit density (EPD) profiles in HgCdTe(100) layers grown on GaAs(100) by metalorganic chemical vapor deposition. D islocation profiles in HgCdTe(111)B and HgCdTe(100) layers differ as f ollows: Misfit dislocations in HgCdTe(111)B layers are concentrated ne ar the HgCdTe/CdTe interfaces because of slip planes parallel to the i nterfaces. Away from the HgCdTe/CdTe interface, the HgCdTe(111)B dislo cation density remains almost constant. In HgCdTe(100) layers, however , the dislocations propagate monotonically to the surface and the disl ocation density decreases gradually as dislocations are incorporated w ith increasing HgCdTe(100) layer thicknesses. The dislocation reductio n was small in HgCdTe(100) layers more than 10 mu m from the HgCdTe/Cd Te interface. The CdTe(100) buffer thickness and dislocation density w ere similarly related. Since dislocations glide to accommodate the lat tice distortion and this movement increases the probability of disloca tion incorporation, incorporation proceeds in limited regions from eac h interface where the lattice distortion and strain are sufficient. We obtained the minimum EPD in HgCdTe(100) of Ito 3 x 10(6) cm(-2) by gr owing both the epitaxial layers more than 8 mu m thick.