Dislocation density reduction by thermal annealing of HgCdTe epilayers grown by molecular beam epitaxy on GaAs substrates

Abstract

Post growth thermal annealing has been used to reduce the threading dislocation density of Hg1−xCdxTe (0.20≤x≤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 °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 (1×105 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.