Compliant epitaxy of III-V compound semiconductors for optoelectronic device applications.

摘要

This work uses two approaches to take advantage of the design freedoms allowed through compliant epitaxy growth techniques. The first technique is a method using strain relaxation of In_0.25Ga_0.75As grown on GaAs through lateral oxidation of an underlying Al_0.98Ga _0.02As layer. Following the oxidation process, thicker (∼1 μm) lattice-matched layers are regrown onto the relaxed structures. In addition, strained In_0.40Ga_0.60As quantum wells were grown in an In_0.25Ga_0.75As matrix in an effort to achieve 1.3 μm emission from the regrown material.; The regrown material was found to have equal threading dislocation densities as the underlying In_0.25Ga_0.75As template layers. In addition, room-temperature photoluminescence (PL) measurements indicate the presence of photon emission with wavelengths near 1.1 μm for regrown In _0.25Ga_0.75As layers. Successful regrowth of In_0.25Al _0.75As was also demonstrated using similar techniques. Hall-effect measurements were performed to evaluate the carrier concentration of In_0.25Ga _0.75As and In_0.25Al_0.75As epilayers doped with Si and Be. Normal doping behavior was seen in the In_0.25Ga _0.75As films, but the In_0.25Al_0.75As films have lower carrier concentrations than would be expected, indicating the presence of deep-level electronic traps in the material. Finally, PL characterization of strained In_0.40Ga_0.60As quantum wells, taken at a temperature of 77K, indicated photon emission at wavelengths near 1.23 μm.; The second technique uses a novel approach: very-low temperature molecular beam epitaxy (VLT-MBE) which involves growth of amorphous and polycrystalline materials. Using GaP and laterally oxidized AlAs materials, substrate independent DBRs were fabricated at wavelengths in both the visible spectrum, 480 nm to 550 nm, as well as those used in the telecommunications industry, 1310 nm to 1550 nm. In addition, VLTMBE-grown InGaP was used as a protection layer during post-growth oxidation processes. These InGaP layers were used to protect the In_0.25Ga_0.75As layers, mentioned above, during the lateral oxidation relaxation process. The VLT-grown InGaP films were found to be superior to other protection layers, such as SiN_x and SiO ₂, due to their ability to allow dislocation reduction during the oxidation process. Because of the nature of the VLT-grown materials, they can be used in any material system using a variety of host-substrates, making this growth technique highly adaptable and useful.