LPE HgCdTe on sapphire status and advancements

With the evolution of infrared arrays to over four million pixels, larger f ormats have demanded higher quality mercury cadmium telluride (MCT) wafers. Since single defects can easily degrade multiple diodes, high operability requires very homogeneous and nearly flawless epitaxial surfaces. Subsequen t photolithography and hybridization also demand unprecedented levels of su bstrate flatness and low imperfections. To consistently and reliably produc e large area arrays, Insaco Inc., The Boeing Company, and Rockwell Internat ional Corporation have developed major quality improvement procedures which address all three components of the infrared material wafer architecture. Centered on the producible alternative to cadmium telluride for epitaxy (PA CE) process, technological advancements encompassed sapphire substrates, or ganometallic vapor phase epitaxy (OMVPE), cadmium telluride (CdTe) buffer l ayer growth, and liquid phase epitaxial (LPE) mercury cadmium telluride gro wth. Processed material from these runs mated to Conexant(TM) fabricated mu ltiplexers have successfully produced 1024 x 1024 and the first 2048 x 2048 IR short-wave (2.5 mum at 80 K) hybrid focal plane arrays. Operabilities i n these implanted n-on-p junction devices reach 99.98% with near 70% quantu m efficiency in the astronomy 'K' band (2.2-2.4 microns).