Jack P. Salerno

Low‐dislocation‐density GaAs epilayers grown on Ge‐coated Si substrates by means of lateral epitaxial overgrowth

Single‐crystal GaAs layers have been obtained by means of lateral epitaxial overgrowth seeded within stripe openings in a SiO2 mask over GaAs layers grown on Ge‐coated Si substrates. Transmission electron microscope and scanning cathodoluminescence studies indicate that the laterally overgrown GaAs layers have a dislocation density of less than 104 cm−2, compared to 107–108 cm−2 for the GaAs layers grown directly on the Ge/Si substrates. Initial experiments indicate that the electrical properties of the laterally overgrown layers are comparable to those of conventional GaAs epilayers grown on single‐crystal GaAs substrates.

Epitaxy Of GaAs on Si: MBE and OMCVD

Growth technique dependent factors are compared for molecular beam epitaxy (MBE) and organometallic chemical vapor deposition (OMCVD) that are related to the GaAs on Si epitaxy. The comparison, both for growth processes and as-grown material characteristics, indicates that material qualities of these layers provided by the two growth techniques are comparable in many aspects, but differ in morphological texture, residual stress, and occasionally Schottky barrier height. These issues are discussed further with our recent OMCVD results in order to ensure the OMCVD advantages for GaAs on Si wafer engineering, which are referred as an easy scale-up and a large throughput.

Low-threshold GaAs/AlGaAs lasers grown on Si by organometallic vapor phase epitaxy

Low‐threshold double‐heterostructure ridge‐waveguide lasers have been fabricated in GaAs/AlGaAs layers grown on Si by organometallic vapor phase epitaxy. The pulsed threshold current of the best ridge‐waveguide laser is 50 mA, with differential quantum efficiency of about 9% per facet. Broad‐area lasers fabricated on the same wafer have pulsed threshold current densities as low as 300 A/cm2 .

Transmission electron microscopy of GaAs grown over submicrometer‐period tungsten gratings

The GaAs overgrowth of tungsten gratings, the most critical step in the fabrication of the permeable base transistor (PBT), has been characterized by transmission electron microscopy (TEM). The 3200‐A‐period tungsten base gratings for the PBT are very uniform in linewidth and spacing before the GaAs overgrowth, and this uniformity is preserved after the overgrowth. Both voids and stacking faults are observed in the epitaxial GaAs grown over the gratings. An unexpected result of this study is the observation that a considerable density of such defects can be present in a PBT wafer that yields uniform, high‐frequency devices.

Electronic Properties of Grain Boundaries in GaAs: A Study of Oriented Bicrystals Prepared by Epitaxial Lateral Overgrowth

Abstract : The electronic properties of grain boundaries in GaAs have been investigated. The optoelectronic properties of melt-grown polycrystalline GaAs were studied by cathodoluminescence. This analysis showed that grain boundary properties are influenced by both the boundary structure and the composition of the matrix. For a systematic investigation of the relationship between grain boundary structure and electronic behavior, a technique has been developed for the growth of oriented GaAs bicrystal layers by vapor-phase epitaxy using lateral overgrowth. Using this technique, a series of n-type bicrystal layers containing 110/(111) tilt boundaries with selected misorientation angles ranging from 0 to 30 degrees were grown.