MWIR focal plane arrays made with HgCdTe grown by MBE on germanium substrates

Abstract

The possibility to grow HgCdTe by Molecular Beam Epitaxy (MBE) on large alternative substrates opens the way of increasing the size and reducing the cost of infrared FPAs operating in the Medium Wave InfraRed (MWIR) bands. Germanium was chosen several years ago at Leti because its 'in situ' and 'ex situ' surface preparations are much easier to control compared to the more conventionally used silicon alternative substrate. Moreover extremely high quality germanium "epiready" substrates are commercially available at a reasonable cost for wafer sizes up to 8 inches. MWIR HgCdTe wafers grown today by Defir (LETI/Sofradir joint laboratory) on germanium (up to 4 inches diameter) using MBE, exhibit electrical and physical properties that enables the fabrication of FPAs with various sizes (320x256, 640x512, 1280x1024) and pitches (from 30µm to 15µm) with electro-optical performances similar to the standard process based on the more conventional epilayers of HgCdTe grown on CdZnTe by Liquid Phase Epitaxy (LPE). Due to the low microscopic and macroscopic defect density that can be obtained on such wafers, operabilities above 99.9% are reached today. A status of this MBE growth technology is presented as well as the FPAs performances, including conventional industrial products manufactured such as 320x256 (pitch 30µm), 640x512 (pitch 15µm) and the largest 1280x1024 (pitch of 15µm) more recently available.

Morphology issues of HgCdTe samples grown by MOCVD

“…We have intended to test surface morphology using alternative to MOCVD growth method. Increasing number of reports presenting high quality and mirror like HgCdTe(100) heterostructures fabricated by MBE [18][19][20] inclined us to deposit several CdTe buffers by this method. These CdTe buffer layers were deposited by MBE system in Institute of Physics Polish Academy of Science, Warsaw.…”