Growth and characterization of IV-VI semiconductor multiple quantum wells

Multiple quantum well structures of PbS/PbSe layers were grown on (111)-oriented BaF$\sb2$ substrates using hot-wall epitaxy. These structures were characterized using Auger electron spectroscopy, X-ray photoelectron spectroscopy, Rutherford backscattering spectroscopy and x-ray diffraction. Angle resolved XPS showed that the PbS interdiffused into the PbSe approximately 30 A in 30 minutes at 300 C. The Rutherford backscattering measurements revealed that the interdiffusion at the PbS/PbSe interface is small and quantitatively similar to the interdiffusion of PbS on the BaF$\sb2$ substrate. Depth profiling Auger electron spectroscopy of a multiple quantum well structure confirmed the modulation of its composition along the sample's thickness. Though it was expected that the thin layers of the PbS and PbSe constituting the structures would be strained due to the lattices mismatch between these two materials ($\Delta$a$\sb{\rm o}$/a$\sb{\rm o}$ = 0.03), no indication of this strain could be established from the x-ray diffraction data. The energy band alignment at the PbSe/PbS interface was determined to be of the type I with a conduction energy band offset $\Delta$E$\sb{\rm c}$ = 48 meV. This was done by studying the thermal activation behavior of the photocurrent of a Pb-PbS/PbSe based Schottky structure. The magnetotransport properties of PbS/PbSe multiple quantum wells was studied in a temperature range 280 $<$ T $<$ 4.2. The magnetic field dependence of the Hall voltage indicates the presence of two types of carriers with different mobilities in the samples. This was explained by proposing a quantum well energy level structure with different electrical sub bands on the wells which arise from the multivalley band structure and the effective mass anisotropy found in bulk PbSe and PbS.