GSMBE growth and characterization of InxGa1-xAs/InP strained-layer MQWs in a P-i-N configuration

InxGa1-xAs/InP (0.39 less than or equal to x less than or equal to 0.68) strained-layer quantum wells having 20 wells with thickness of 50 Angstrom in a P-i-N configuration were grown by gas source molecular beam epitaxy (GSMBE). High-resolution X-ray diffraction rocking curves show the presence of up to seven orders of sharp and intense satellite reflection, indicative of the structural perfection of the samples. Low-temperature photoluminescence and low-temperature absorption spectra were used to determine the exciton transition energies as a function of strain. Good agreement is achieved between exciton transition energies obtained experimentally at low temperature with those calculated using the deformation potential theory.

Dissociated screw dislocation which can relieve strain energy in the epitaxial layer of GeSi on Si(001)

A dissociated screw dislocation parallel to the interface was found in the epitaxial layer of the Ge0.17Si0.83 Si(001) system. It is shown that this dissociated screw dislocation which consists of two 30 degrees partials can relieve misfit strain energy, and the relieved misfit energy is proportional to the width of the stacking fault between the two partials.

Characterization and improvement of GaAs layers grown on Si using an ultrathin a-Si film as a buffer layer

GaAs epilayers grown on Si by metalorganic chemical vapor deposition (MOCVD) using an ultrathin a-Si buffer layer were characterized by deep-level transient spectroscopy (DLTS). Six electron traps with activation energies of 0.79, 0.67, 0.61, 0.55, 0.53 and 0.32 eV below the conduction band were determined by fitting the experimental spectra. Two of the levels, C (0.61 eV) and F (0.32 eV), were first detected in GaAs epilayers on Si and identified as the metastable defects M3 and M4, respectively. In order to improve the quality of GaAs/Si epilayers, another GaAs layer was grown on the GaAs/Si epilayers grown using MOCVD. The deep levels in this regrown GaAs epilayer were also studied using DLTS. Only the EL2 level was found in the regrown GaAs epilayers. These results show that the quality of the GaAs epilayer was greatly improved by applying this growth process.

A transition layer model and its application to resonant tunneling in heterostructures

A transition layer model is proposed and used to calculate resonant tunneling in a double-barrier quantum well system. Compared with the ideal step of the potential at the interface, the studied system has transition layers that are composed by many thin rectangular barriers with a random height. It is found that these transition layers can improve the peak-to-valley ratio of the tunneling current and change the negative differential conductance.