DISLOCATION DENSITY REDUCTION BY THERMAL ANNEALING OF HGCDTE EPILAYERS GROWN BY MOLECULAR-BEAM EPITAXY ON GAAS SUBSTRATES

Post growth thermal annealing has been used to reduce the threading dislocation density of Hg1-x Cd(x) Te (0.20 less-than-or-equal-to x less-than-or-equal-to 0.28) epilayers grown on (211)B GaAs substrates by molecular beam epitaxy. Etch pit density studies indicate an order of magnitude reduction on the surface threading dislocations after annealing at 490-degrees-C for 30 min. The dislocation density at the HgCdTe surface on this highly mismatched system is only a factor of 2-6 times higher than the best values (1 x 10(5) cm-2) we have obtained using CdZnTe bulk lattice-matched substrates. The reduction of dislocations may be due to enhanced dislocation movement and their annihilation and coalescence at Hg vacancies point defect pinning centers introduced during the annealing process.