Heteroepitaxial 96 x 128 lead chalcogenide on silicon infrared focal plane array for thermal imaging

Abstract

Narrow gap IV-VI (lead chalcogenides like PbSnSe and PbTe) layers grown epitaxially on Si(111)-substrates by molecular beam epitaxy exhibit high quality despite the large lattice and thermal expansion mismatch. Line arrays in IV-VI on Si layers have so far been realized and described. We present the first realization of a 2-d narrow gap IR-FPA on a Si-substrate containing the active addressing electronics: A 96 X 128 array with 75 μm pitch for row-by-row electronic scanning and parallel read-out of the line addressed. Each pixel contains a bare Si-area onto which epitaxial growth occurs, and an access transistor. A MWIR PbTe layer is grown by MBE onto complete Si-read-out substrates at temperatures below 450°C (because of the Al-metallization). Photovoltaic sensors are then delineated in the layers. Each pixel is connected to the Si read-out by sputtered Al-stripes. Yield in completely fabricated arrays was up to above 97%, with quantum efficiencies around 60% and differential resistances at zero bias of several 100 kOhms.