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1

Status of HgCdTe photodiodes at the Military University of Technology

Kubiak L., Madejczyk P., Wenus J., Gawron W., Jóźwikowski K., Rutkowski J., Rogalski A.

Opto-Electronics Review

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2003

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Vol. 11, No. 3

211-226

EN

The paper presents technological achievements in fabrication of cryogenically-cooled and ambient temperature HgCdTe photodiodes carried out during the last four years at the Institute of Applied Physics, Military University of Technology. Because of the complicated and expensive fabrication process, numerical simulation has become a critical tool for the development of HgCdTe bandgap engineering devices. Therefore in the second part of the paper, an original interation scheme is used to predict the effect of composition and doping profiles on the heterojunction detector parameters. A novel tipping boat for liquid phase epitaxial (LPE) growth of HgCdTe from Te-rich solutions has been proposed. The successful fabrication of long wevelength infrared (LWIR) Hg1-yCdyTe/Hg1-xCdxTe heterostructures (y x) on semi-insulating (111)CdZnTe substrates is presented. The performance of p-on-n double-layer heterojunction (DLHJ) photodiodes at temperature 77 K is analysed. It is also shown that LPE can be used to realise advanced bandgap engineered multi-junction structures. The parameters and characteristics of the new type of HgCdTe buried photodiodes, operated at near-room temperature (T = 200-300 K) in LWIR spectral range, are reported. Finally, an effective numerical model for performance predictions of HgCdTe heterostructure device is presented. The model is used to analyse the performance of dual-band HgCdTe photovoltaic detector and mid wavelength infrared (MWIR) HgCdTe heterostructure device. In the last case, it is shown that excess 1/f noise of MWIR non-equilibrium heterostructure device is connected with fluctuation of carrier mobility.

2

Analysis of VLWIR HgCdTe photodiode performance

Wenus J., Rutkowski J., Rogalski A.

Opto-Electronics Review

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2003

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Vol. 11, No. 2

143-149

EN

The performance of very long wavelength infrared (VLWIR) HgCdTe photodiodes at temperatures ranging from 77 K up to 150 K is presented. The effect of inherent and excess current mechanisms on quantum efficiency and dynamic resistance-area RA product is analysed. Different methods of determining the ideality factor are shown and among them the one based on the use of RA product versus bias voltage proves to be most reliable. At higher temperatures, however, the calculated ideality factor does not give any useful information about the nature of the p-n junction current due to significant influence of the series and shunt resistances. A comparison of the experimental data with the results of analytical and numerical calculations shows that the photodiodes with cut-off wavelength up to 14.5 um are diffusion-limited at temperatures exceeding 100K.

3

Inherent and additional limitations of HgCdTe heterojunction photodiodes

Rutkowski J., Wenus J.

Opto-Electronics Review

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2001

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Vol. 9, No. 3

331-335

EN

The performance of P-on-n double-layer heterojunction (DLHJ) HgCdTe photodiodes at temperature of 77 K is presented. The effect of inherent and excess current mechanisms on quantum efficiency and R₀A product is analysed. The diodes with good R₀A operability, high quantum efficiency, and low 1/f noise have been demonstrated at cutoff wavelengths up to 14 mm. The experimental results show that proper surface passivation and low series/ contact resistance are major issues relating to fabrication of HgCdTe detectors with high performance.

4

Gate-controlled narrow band gap photodiodes passivated with RF sputtered dielectrics

Rutkowski J., Wenus J., Gawron W., Adamiec K.

Opto-Electronics Review

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1999

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Vol. 7, No. 2

97-101

EN

Gate-controlled diodes were made by using evaporated indium electrodes overlapping the edge of mesa diodes, isolated from the surface by a layer of ZnS or by native anodic oxide of InSb or HgCdTe. The resulting three-terminal device characteristics with gate voltage as a parameter have been investigated. Relative spectral responses and I-V characteristics were measured at 77 K. The R₀A product is used as an indicator of the dark current of photodiodes passivated with ZnS layer. A plot of R₀A values versus gate potential shows that the optimum R₀A values are obtained at small positive gate bias voltage. This dependence is consistent with surface recombination influencing the R₀A product. The results of a two-dimensional model for calculating gate-induce surface leakage currents due to band-to-band tunnelling are presented. The exact quantitative comparison cannot be made between our results and theory, since the active tunnelling area is not known.