Relaxation of stresses in CdTe layers grown by molecular beam epitaxy

Abstract

X-ray diffraction has been used to study CdTe layers grown by molecular beam epitaxy on Cd0.96Zn0.04Te or InSb substrates with either (111) or (001) orientation. The layers are elastically strained up to a critical thickness, above which misfit dislocations are generated. Our experimental determinations of the critical thickness and the relaxation of the stress while increasing the layer thickness are different from predictions of the existing models. We present a discussion of relaxation based on the determination of the minimum energy state of the layer for a given thickness. We show that above the critical thickness, the layer relaxes so that the product of the stress by the thickness remains constant. This constant has been experimentally determined for both (111) and (001) orientation.

MBE HgCdTe on Alternative Substrates for FPA Applications

“…In a highly lattice-mismatched system, the threading dislocations are promoted by the misfit strain 16 at the coincidence interface 17 (a two-layer composite between the substrate and the epilayer). The density of threading dislocations can be reduced by modifying the coincidence interface to assist strain relaxation.…”

Strain relaxation of CdTe films growing on lattice-mismatched substrates

“…Since the lattice constant of CdTe (6.480 Å) is much larger than that of GaAs (5.653 Å) and Si (5.431 Å), (111) oriented cubic CdTe films have been found to grow on these (001) oriented substrates [5][6][7][8][9][10] in order to minimize the surface free energy. We discuss the properties of CdTe films grown on these two substrates separately.…”

“…Unlike CdTe films grown on Si(100), the CdTe domains in the CdTe(111) GaAs(001) films are compressed along the [1][2][3][4][5][6][7][8][9][10] direction while extended along the [110] direction [12]. Furthermore, CdTe's thermal expansion coefficient (4.8 × 10 −6 /K) is smaller than GaAs (6.0 × 10 −6 /K).…”

“…The decrease in both the splitting and the band-gap energy indicates that the strain is relaxed to some extent with increasing the film thickness. [1][2][3][4][5][6][7][8][9][10], in which the lattice mismatch is reduced to 16 and 3% along the [1][2][3][4][5][6][7][8][9][10] and directions, respectively. The domains are compressed in both directions [6,16], which is different from the case of CdTe grown on GaAs(001) [17].…”

“…In particular, CdTe films can be grown by a number of techniques, including molecular beam epitaxial (MBE) [5,6], metalorganic chemical vapor deposition (MOCVD) [7], and laser-assisted epitaxy or pulsed-laser deposition (PLD) [8][9][10]. In general, thin films grown epitaxially on a latticematched substrate have been found to have crystalline quality comparable or even better than of the bulk crystals.…”