Structural defects in MBE-grown CdTe-basing heterojunctions designed for photovoltaic applications

Abstract Structural defects in the p -ZnTe/ i -CdTe/ n -CdTe single-crystalline heterojunctions designed for photovoltaic applications have been investigated by transmission electron microscopy (TEM) and deep-level transient spectroscopy (DLTS). Lattice parameters misfit strain undoped cadmium telluride (CdTe) absorber layers of heterojunctions, grown molecular-beam epitaxy technique on two different substrates, GaAs CdTe, determined with high-resolution x-ray diffractometry. A dense network dislocations at lattice-mismatched CdTe/GaAs ZnTe/CdTe interfaces numerous threading stacking faults shown cross-sectional TEM imaging heterojunctions. The DLTS measurements revealed five traps only three them CdTe. Four attributed to electronic states extended defects, presumably dislocations, grounds their logarithmic capture kinetics charge carriers. Two these traps, displaying largest values cross-section properties characteristic bandlike states, ascribed core dislocations. It is argued that they are most likely responsible decreased lifetime photo-excited carriers resulting a low energy conversion efficiency solar cells based similarly