IRFPA technology utilizing HgCdTe/Si: successes, roadblocks, and material improvements

Mercury Cadmium Telluride (HgCdTe) is the material of choice for the majority of high performance infrared focal plane array (IRFPA) systems fielded in the Army with state-of-the-art HgCdTe growth using a bulk Cadmium Zinc Telluride (CdZnTe) substrate. However, as the push for larger array sizes continues, it has been recognized that an alternative substrate technology will be required for HgCdTe IRFPAs. A major effort has been placed in developing CdTe/Si as such a substrate. Although successful for short-wavelength (SWIR) and mid-wavelength (MWIR) focal plane arrays, current HgCdTe/Si material quality is insufficient for long-wavelength (LWIR) arrays due to the high density of dislocations present in the material. In this paper, we will discuss several processes being developed at the U.S. Army Research Laboratory (ARL) to overcome this issue. Effort has been placed on both composite substrate development and improvement, and on HgCdTe/Si post-growth processes. Recently, we have demonstrated HgCdTe/Si material with dislocation density measuring 1 × 106 cm-2. This is a five times reduction in the baseline material dislocation density currently used in the fabrication of devices.