Critical thickness and strain relaxation in lattice mismatched II–VI semiconductor layers

Abstract

Critical thickness hc has been calculated for capped and uncapped lattice mismatched II–VI semiconductor epilayers. Both the old equilibrium theory and the improved theory have been used. The calculated values are compared with the experimental data on epilayers of several II–VI semiconductors and alloys. The observed values of hc are larger than the calculated values, a result similar to that observed with GeSi and InGaAs strained layers. The discrepancy is attributed to the difficulty in nucleating the dislocations. Strain relaxation in layers with thickness h>hc is also calculated. Observed strain relaxation in ZnSe layers grown on (100) GaAs shows good agreement with the equilibrium theory. In other cases, the observed relaxation is sluggish and the residual strain is larger than the calculated value. Many authors have observed that strain near the surface of the II–VI epilayers is small and increases as the depth increases. We describe an improved model to explain this observation. The agreement between the prediction of our model and the observed strain distribution is excellent. A new model based on continuum elasticity theory is described to explain strain oscillations during the initial stages of growth of highly mismatched layers. In highly mismatched layers, the dislocations are distributed uniformly. A model to interpret this observation is suggested.

Relevance of Thermal Mismatch in Large-Area Composite Substrates for HgCdTe Heteroepitaxy

“…According to Cohen-Solal et al 19 and Pinardi et al, 20 experimental measurements on II-VI semiconductor epilayers (including CdTe) have produced the semi-empirical relationship, 0.45(e i-misf ) -3/2 , to estimate the critical thickness. Using this method, we calculated critical thickness values (at the growth temperature), of 4.8 Å , 8.8 Å , and 8.9 Å for CdTe/Si, CdTe/Ge, and CdTe/GaAs, respectively.…”

Role of thermal expansion matching in CdTe heteroepitaxy on highly lattice-mismatched substrates

“…We have estimated h c using a semi-empirical approximation given by Cohen-Solal et al [16] and Pinardi et al [17];…”

Surface reconstructions of II‐VI compound semiconductor surfaces

“…On one hand this material is interesting for electro-optical applications and has been the object of many investigations over the past ten years [8][9][10][11][12]. On the other hand it is also interesting for the investigation of basic properties due to the extreme mass asymmetry of its compounds.…”