Vanya Srivastav

Performance study of high operating temperature HgCdTe mid wave infrared detector through numerical modeling

The design of present generation uncooled Hg1-xCdxTe infrared photon detectors relies on complex heterostructures with a basic unit cell of type (n) under bar (+)/pi/(p) under bar (+). We present an analysis of double barrier (n) under bar (+)/pi/(p) under bar (+) mid wave infrared (x = 0.3) HgCdTe detector for near room temperature operation using numerical computations. The present work proposes an accurate and generalized methodology in terms of the device design, material properties, and operation temperature to study the effects of position dependence of carrier concentration, electrostatic potential, and generation-recombination (g-r) rates on detector performance. Position dependent profiles of electrostatic potential, carrier concentration, and g-r rates were simulated numerically. Performance of detector was studied as function of doping concentration of absorber and contact layers, width of both layers and minority carrier lifetime. Responsivity similar to 0.38 A W-1, noise current similar to 6 x 10(-14) A/Hz(1/2) and D* similar to 3.1 x 10(10)cm Hz(1/2) W-1 at 0.1 V reverse bias have been calculated using optimized values of doping concentration, absorber width and carrier lifetime. The suitability of the method has been illustrated by demonstrating the feasibility of achieving the optimum device performance by carefully selecting the device design and other parameters

Modeling of room temperature current-voltage measurements on homo-junction HgCdTe diodes exhibiting nonequilibrium effects

HgCdTe mid wave infrared (MWIR) n+/ν/p+ homo-junction photodiodes with planar architecture are designed, fabricated, and measured at room temperature. An improved analytical I-V model is reported by incorporating trap assisted tunneling and electric field enhanced Shockley-Read-Hall generation recombination process due to dislocations. Tunneling currents are fitted before and after the Auger suppression of carriers with energy level of trap (Et), trap density (Nt), and the doping concentrations of n+ and ν regions as fitting parameters. Values of Et and Nt are determined as 0.79 Eg and ∼9 × 1014 cm−3, respectively, in all cases. Doping concentration of ν region was found to exhibit nonequilibrium depletion from a value of 2 × 1016 to 4 × 1015 cm−3 for n+ doping of 2 × 1017 cm−3. Pronounced negative differential resistance is observed in the homo-junction HgCdTe diodes.

Modeling Current Voltage Characteristics of MWIR HgCdTe Diodes at High Reverse Bias Voltage

In this paper we model the current voltage (I–V) characteristics of Hg1 − xCdxTe (x = 0.3) diodes at high reverse bias voltage. The breakdown characteristics are indicative of n+/n−/p kind of doping profile. Various current limiting mechanisms affecting the soft breakdown characteristics of Hg1 − xCdxTe diodes have been identified. We also found that the existing models do not accurately fit the I–V curves above a certain reverse bias voltage, which led us to investigate possible additional dark current mechanisms responsible for this kind of behavior. Thus, a new current limiting model is also proposed in this paper.