Transmission Electron Microscopy Study of HgTe/CdHgTe Quantum Wells

Bright-field transmission electron microscopy has been used for the study of two HgTe/CdHgTe single quantum wells (QW) with the thickness of $\sim 10$ nm grown by molecular beam epitaxy on GaAs substrate with ZnTe/CdTe buffer layers. The quantum well barriers were fabricated from CdHgTe with CdTe molar fraction (composition) $\sim 0.7$ . The importance of an extra CdHgTe layer (in the studied case, with composition of $\sim 0.9)$ placed between the CdTe buffer and the QW structure for the reduction of the density of defects both in the barrier layers and in the well itself was demonstrated. The defects in the latter were studied with high-resolution transmission electron microscopy and tentatively identified as stacking faults, dislocations and dislocation loops.