Molecular beam epitaxial development of AlSb on Silicon substrates for radiation detector applications

The detection technology for X-rays and gamma-rays has been significantly improved in the past decade through bulk crystal growth efforts, particularly in the development of Cadmium Zinc Telluride (CZT). There is significant effort underway to develop newer bulk crystal technologies such as Cadmium Manganese Telluride (CMT) in order to achieve higher detection efficiency, energy resolution, room-temperature operation, as well as the ability to produce such detectors at reasonable cost. A possible alternative to bulk crystals could be the use of epitaxially grown structures which could pave the way for heterostructures, avalanche detectors, and CMOS integration.

In this presentation we demonstrate molecular beam epitaxy (MBE) based growth of highly resistive AlSb on Silicon substrates. AlSb a compound semiconductor with good potential for making room-temperature radiation detectors due to antimony’s high atomic number (Sb = 51), a reasonably wide bandgap of 1.6 eV and high room temperature carrier mobility for both electrons and holes. The study will include the growth of AlSb on miscut silicon substrates using the interfacial misfit dislocation growth mode. This allows for the simultaneous accommodation of the large mismatch between the substrate and the epilayer while also suppressing antiphase domains. The result is a low threading dislocation AlSb layer that can be grown up to 10 µm thick with minimized threading dislocations and thermal expansion coefficient mismatch. The presentation will include high resolution transmission electron microscopy, hall measurements, X-Ray diffraction studies, microwave photoconductive decay studies, and diode analysis.