LWIR HgCdTe photovoltaic detectors for hybrid focal plane arrays

High performance second generation infrared imaging systems require high density focal plane arrays which utilize intrinsic HgCdTe photodiodes for photon detection and Si CCD signal processors in a hybrid configuration. Limitations on system performance are established by both input circuit as well as detector requirements. In the paper performance of LWIR photodiodes in the 8-12 µm spectral region will be discussed. LWIR HgCdTe photodiodes have been fabricated by two basic techniques: ion implantation and liquid phase epitaxial heterojunctions. In the 8-12 µm region dark current components include diffusion, generation-recombination, tunneling and surface leakage currents. Each of these components may be minimized and therefore performance maximized by proper choice of material parameters and device design. In this paper a tradeoff analysis including thin base lateral diffusion (TBLD) as well as heterojunction (HJ) design concepts utilized to minimize dark current sources will be presented. A review of recent and current work on HgCdTe ion implantation and heterojunction technology including material growth, surface passivation and device fabrication will be presented and experimental results compared with predicted device performance.