Hg1−xCdxTe crystals with x˜0.2 were grown by the traveling heater method (THM), in either the [111]A or [1 1 1]B directions, using oriented CdTe seeds. Twins are sometimes formed during the growth of these crystals. In crystals grown in the [111]A direction the twins, of orientation [5 1 1]B, are constantly growing at the expense of the original [111]A oriented grain. Growth in the [1 1 1]B direction, on the other hand, suppresses the growth of the twin domain. Photodiodes and capacitors realized on the (111)A plane are markedly superior to those on the twin plane, [5 1 1]B. The difference is due to higher fixed charge and larger fast surface state densities in the case of the [5 1 1]B plane. These effects are explained by the lattice structures in the {111} and {511} planes and their possible influence on surface reactivity.