C. X. Wang

Antimony segregation in GaAs-based multiple quantum well structures

Sb segregation effects have been studied in structures grown by organometallic vapor phase epitaxy. The structures are formedby periodic exposure of the GaAs (0 0 1) surface to trimethylantimony (TMSb), followedby GaAs growth. Reflectance-difference spectra obtained during growth show a strong influence of Sb on the surface reconstruction, reducing the concentration of As dimers. Transmission electron microscope images and X-ray diffraction (XRD) measurements show that a periodic multiple quantum well (MQW) structure is formed by the TMSb/GaAs growth sequence. A fraction of the deposited Sb is incorporated as a one monolayer thick Sb-rich quantum well in each period. The incorporation of impurity Sb, as the GaAs layers are grown, results in the formation of a graded GaAs1� xSbx barrier layer above each QW layer. The impurity profile inferredfrom XRD measurements is in goodagreement with a one-dimensional segregation model based on the partitioning of Sb between the growing barrier layer and a surface floating layer. The Sb floating layer is shown to desorb under exposure to tertiarybutylarsine. r 2003 Elsevier Science B.V. All rights reserved.

Local vibrational modes of carbon in GaSb and GaAsSb

We have measured the Raman spectra of heavily carbon doped (p>1019 cm−3) GaSb and GaAsSb. A local vibrational mode (LVM) due to carbon residing on group-V lattice sites was observed at 540 cm−1 for GaSb and 568 cm−1 for GaAs0.44Sb0.56. A gap mode at 164 cm−1 was observed for GaSb. The frequency of the LVM as well as the gap mode is in quantitative agreement with recent theoretical predictions.

Structural effects of carbon in GaSb grown by metalorganic vapor phase epitaxy

High-resolution X-ray diffraction, Hall effect and secondary ion mass spectrometry measurements (SIMS) were used to study the effect of carbon doping on the lattice constant of GaSb. A linear increase in tensile strain as a function of carbon concentration was observed in the range from 1 x 10 19 to 1 x 10 20 cm -3 . The observed strains are consistent with carbon incorporating as a simple substitutional acceptor up to at least 1 x 10 20 cm -3 . SIMS measurements show that the total carbon concentration is linearly proportional to the CCl 4 source flows, whereas the hydrogen concentration increases super-linearly. Nevertheless, the ratio of hydrogen to carbon is no greater than 9% of the maximum incorporated carbon concentration.

Growth of GaAsSb/InP heterostructures by OMVPE

This paper summarizes several important aspects of the growth of GaAsSb/InP heterostructures for the fabrication of high speed double heterojunction bipolar transistors (DHBTs). Some of the challenges in OMVPE growth of antimonide/phosphide compounds are discussed, including segregation, interface issues, and control of carbon at very high doping levels. We also discuss the effect of hydrogen passivation and the role of atomic ordering and compositional modulation, including its effect on electrical properties.