Investigation of molecular beam epitaxy grown p-type mercury cadmium telluride for infrared detector applications

[Truncated abstract] HgCdTe, a ternary semiconductor compound with a high technological importance, is the material-of-choice for the fabrication of single and multi-element photon detectors utilised in infrared (IR) sensing applications. HgCdTe has a tunable direct bandgap, which can be engineered to respond to spectral wavelengths from 0.7 μm to 30 μm by changing themole ratio of CdTe to HgTe in the alloy. The current preferred growth technique of molecular beam epitaxy (MBE) provides unrivaled degrees of freedom in the growth of large area HgCdTe, due to its low growth temperature, good reproducibility, and its excellent control of thickness, composition, and doping profile, compared to other growth methods. In infrared focal plane array (IRFPA) technology, each pixel in the array is a high performance infrared detector consisting of a p-n junction for detection across a single wavelength band, or multiple p-n layers for multispectral detection. The technology to attain high quality n-type HgCdTe during MBE growth is mature, with electron concentrations between 1015 cm3 and 1018 cm3 and mobilities of up to 105 cm2 V1 s1 being achieved routinely using extrinsic n-type dopants such as indium and iodine. While Group I elements have been successfully utilised as p-type dopants in HgCdTe, they are highly mobile in the crystal lattice, making them unsuitable for advanced structures requiring abrupt, precisely located p-n junctions. In contrast, Group V dopants (of which arsenic is the most often used) are preferred on account of their low diffusivity, high stability, and high solubility in HgCdTe. However, these dopants are also amphoteric in the crystal lattice, exhibiting behaviour that is strongly dependent on the MBE growth conditions.