Development of type II superlattice infrared detectors monolithically integrated on silicon substrates

The project’s objective is the development of an InAs/GaSb type II superlattice (T2SL) medium wavelength infrared photodiode directly grown on Si substrate for the use of an infrared single pixel photodiode. The T2SL has been selected as the replacement for the state-of-the-art CdHgTe (CMT). The use of Si substrate will help with the integration into the Si-based technology by reducing the fabrication process and costs. The T2SL is a photon detector with overlapping multiple quantum well structure and a type 2 bandgap alignment. The T2SL are fabricated using a combination of materials from the group III-V in order to achieve a well-controlled ultra-thin heterostructures using molecular beam epitaxy as a growth technique. The structure within the active region is designed to enhance the performance of the T2SL architecture by manipulating the thickness and doping of each layer. The direct growth of a T2SL structure on the Si substrate has achieved similar structural and optical properties when compared to that grown on the GaAs substrate. The Si architecture has an absorption edge of 5.365μm when measured at 70K: dark current density at -1V is 4x101A/cm2; responsivity (R) peak is 1.2A/W; quantum efficiency (QE) at -0.1V is 32.5%; and specific detectivity (D*) peak is 1x109cmHz½/W. The pπBn has best architecture over GaAs substrate due to the wide bandgap unipolar barrier. The pπBn has an absorption edge of 6.5 μm when measured at 77K: dark current density under -0.6V is 5x10-3A/cm2; R peak is 0.6A/W; QE at 0V and 3.25μm is 23%; and D* peak is 1x1011cmHz½/W. These results demonstrate that the D* of the pπBn structure is just one order of magnitude smaller than the state-of-the-art CMT detector which is 2x1012cmHz1/2W