The general approach and effects of nonequilibrium operation of Auger suppressed HgCdTe infrared detectors are well understood. However, the complex relationships of carrier generation and dependencies on nonuniform carrier profiles in the device prevent the development of simplistic analytical device models with acceptable accuracy. In this work, finite element methods are used to accurately model the devices, including self-consistent, steady-state solutions of PoissonÕs equation and the carrier continuity equations for carrier densities, Boltzmann transport theory, and published models for recombination/generation processes in HgCdTe. Numerical simulations are used to optimize the material structure and doping levels for an Auger suppressed detector with k c = 5.5 lm at 200 K. The optimized detector structure with step doping and compositional profiles is then compared to a device with realistic gradient doping and compositional profiles.

The general approach and effects of nonequilibrium operation of Auger-suppressed HgCdTe infrared photodiodes are well understood. However, the complex relationships of carrier generation and dependencies on nonuniform carrier profiles in the device prevent the development of simplistic analytical device models with acceptable accuracy. In this work, finite element methods are used to obtain self-consistent steady-state solutions of PoissonÕs equation and the carrier continuity equations. Experimental current-voltage characteristics between 120 K and 300 K of HgCdTe Auger-suppressed photodiodes with cutoff wavelength of k c = 10 lm at 120 K are fitted using our numerical model. Based on this fitting, we study the lifetime in the absorber region, extract the current mechanisms limiting the dark current in these photodiodes, and discuss design and fabrication considerations in order to optimize future HgCdTe Auger-suppressed photodiodes.

In this work, finite element methods are used to obtain self-consistent, steady-state solutions of Poisson's equation and the carrier continuity equations. Experimental dark current-voltage characteristics between 120 and 300 K of HgCdTe Auger-suppressed photodiodes with cutoff wavelength of λ c = 10 µm at 120 K are fitted using numerical simulations. Fitting parameters used include the overlap integral |F 1 F 2 | found to vary from 0.29 at 120 K down to 0.20 at 300 K and the Shockley-Read-Hall (SRH) characteristic lifetime found to be of the order of 10 −7 s at all temperatures. Based on this fitting, negative differential resistance observed in the experimental data is attributed to full suppression of Auger-1 processes and partial suppression of Auger-7 processes. Leakage current induced by traps and impurities in the material causing SRH recombination is found to limit the saturation current after Auger suppression.

The electronic properties of semiconductors are highly dependent on carrier scattering mechanisms determined by crystalline structure, band structure, and defects in the material. Experimental characteristics of lattice vibrational modes and free carrier absorption in single-crystal ZnO samples obtained from different sources are presented in this work to provide a further understanding of carrier scattering processes pertaining to electronic properties. Infrared absorption measurements indicate strong absorption peaks due to a combination of optical and nonpolar phonon modes in the 9-13 mm spectral region. The Raman spectra obtained for these samples similarly reveal the presence of these phonon modes. Infrared absorption measurements also demonstrate free carrier absorption in the 3-9 mm spectral region for higher conductivity samples, where a l m dependence is observed with m 5 2.7-3, indicating both longitudinal optical phonon scattering and ionized impurity scattering. From these results, we show that infrared absorption can be used as a routine nondestructive technique to determine the material characteristics and quality of bulk ZnO.