| Sensing systems for mid-infrared wavelengths (2 to 5 mum) have important applications in biomedical, atmospheric and process gas monitoring systems. For lack of a suitable substrate, the full potential of GaSb-based materials, which are particularly suitable for operating in these wavelengths, are not completely realized. Hence, metamorphic growth technology, that allows the growth of semiconductor epilayers of arbitrary composition on any substrate, has been explored for antimony materials in this research. This makes the growth of device layers, containing arbitrary composition of GaSb-based materials, possible on commercially available 6"-GaAs substrates, and thereby reducing fabrication cost.;Homo-junction n-i-p and p-i-n diodes were fabricated on In0.15 Ga0.85Sb metamorphic layers. The dark current and its temperature dependence were measured and the extraction of area and perimeter components of dark current was done. The modeling of the components of dark current suggests that the diode currents were dominated by surface leakage. Surface passivation by silicon nitride and polyimide were investigated and our findings suggest that the former resulted in a better passivated surface. Responsivity measurements show that In0.18Ga0.82Sb diodes, metamorphically grown on GaSb substrates, have a cut-off wavelength of 2270 nm. Finally, hole (beta) and previously unreported electron (alpha) ionization coefficients, at room temperature and 90° C, were extracted from these structures. The results show that alpha > beta for In0.10Ga0.90Sb for both temperatures.;These photodetectors can be implemented in practical receiver systems for mid-infrared applications, such as atmospheric CO2 and methane detection at 2.0 mum. The possibility of growing antimony-based device layers on larger substrates, paves the way for future optoelectronic receiver systems operating at longer wavelengths, where both the photodetector and the amplifier can be integrated in the same module.;Metamorphic growth of In0.15Ga0.85Sb was achieved using gas-source molecular beam epitaxy by growing compositionally graded InxGa1-xSb buffer layers on a GaSb substrate. The effects of growth temperature on the quality of the metamorphic buffer layers along with the etching issues (both wet and dry) of GaSb-based materials were studied. |
