26th Australian Institute of Physics Congress and the Australian and New Zealand Conference on Optics and Photonics

Characterisation of MBE HgCdTe Grown on Novel Buffer Layers

Not scheduled

1h 30m

Belinda Hutchinson Building (The University of Sydney )

Contributed Oral COMMAD - Optoelectronic and Microelectronic Materials and Devices Parallel sessions

Description

HgCdTe remains the leading material system for high performance infrared detection across the infrared spectral bands. However, its full potential is limited by current substrate technologies, particularly CdZnTe (CZT), which, although lattice matched, is expensive, available only in small sizes and difficult to produce. These constraints restrict device architectures, impede the development of curved focal plane arrays and impose significant manufacturing limitations. This work investigates molecular beam epitaxy (MBE) grown buffer layers engineered for high crystalline quality and compatibility with alternative (III-V) substrates and possible subsequent substrate lift off in some applications.
Several MBE grown buffer layer structures are examined, designed both to support high quality HgCdTe epitaxy and to allow controlled delamination of the substrate. Initial structures are grown on CZT substrates, with the intention of transferring the technology to alternative substrates in future work. Buffer layers include CdZnTe/CdTe strained superlattices that can effectively reduce dislocation density in subsequently grown epitaxial layers. Strained superlattices are also studied as dislocation filtering layers (DFL) to reduce dislocation density.
Material quality is evaluated using non contact minority carrier lifetime technique, a relatively new characterisation method for HgCdTe. In addition, laser beam induced current (LBIC) measurements will be used to determine any electrically active defects present in the MBE-grown material. Lifetime and LBIC spatial maps will be presented to assess uniformity across the wafers. Carrier mobility measurements further benchmark transport properties and assess defect related scattering within each buffer configuration.
The performance of these novel buffer structures is compared with standard MBE grown HgCdTe layers deposited directly on CZT. Results demonstrate the strong potential of engineered MBE grown buffer layers to enable next generation HgCdTe epilayers suitable for curved focal plane arrays and substrate free infrared detector structures.