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1

High-operating temperature MWIR nBn HgCdTe detector grown by MOCVD

Kopytko M., Kębłowski A., Gawron W., Madejczyk P., Kowalewski A, Jóźwikowski K

Opto-Electronics Review

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2013

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Vol. 21, No. 4

402-405

EN

The paper reports on the first experimental results of the mid-wave infrared (MWIR) HgCdTe barrier detectors operated at near-room temperatures and fabricated using metal organic chemical vapor deposition (MOCVD). SIMS profiles let to compare projected and obtained structures and reveals interdiffusion processes between the layers. Undesirable iodine diffusion from cap to the barrier increase the valance band offset and is the key item in limiting the performance of HgCdTe nBn detector. However, MOCVD technology with a wide range of composition and donor/acceptor doping and without post grown annealing might be successfully adopted for barrier device architectures.

2

Teoretyczna analiza właściwości heterozłącza pP⁺ w temperaturze pokojowej za pomocą zaawansowanej symulacji komputerowej

Gawron W., Jóźwikowski K., Kopytko M.

Biuletyn Wojskowej Akademii Technicznej

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2011

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Vol. 60, nr 4

161-176

PL

Artykuł przedstawia wyniki obliczeń teoretycznych parametrów heterozłącza pP⁺ w temperaturze pokojowej wykonanych za pomocą zaawansowanej symulacji komputerowej. Dla porównania przedstawiono także wyniki obliczeń parametrów heterozłącza N⁺p. Wszystkie obliczenia wykonane są dla temperatury 300 K przy oświetlaniu złącza od strony obszaru silnie domieszkowanego promieniowaniem o długości fali 10,6 µm. Wykorzystano oryginalne metody i programy komputerowe opracowane w Zakładzie Fizyki Ciała Stałego.

EN

We report on the results of theoretical calculation of near-room temperature HgCdTe pP⁺ heterojunction. The calculated parameters of pP⁺ junction were compared with parameters of N⁺p junction. All the analyses were done under 300 K temperatures after illuminating the structure from a highly doped layer by the light with a wavelength of 10.6 µm. We have taken advantage of original methods of numerical simulation using computer programmes prepared at the Institute of Applied Physics.

3

High frequency response of near-room temperature LWIR HgCdTe heterostructure photodiodes

Kopytko M., Jóźwikowski K., Jóźwikowska A., Rogalski A.

Opto-Electronics Review

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2010

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Vol. 18, No. 3

277-283

EN

The high frequency response of near-room temperature long wavelength infrared (LWIR) HgCdTe heterostructure photodiodes is investigated using a Fourier space method. The MOCVD HgCdTe multilayer heterostructures were grown on GaAs substrates. The response time of devices as a function of bias has been measured experimentally by using 10-μm quantum cascade laser and fast oscilloscope with suitable transimpedance amplifier. Results of theoretical predictions are compared with experimental data. It is shown that the response time at weak reverse bias condition is mainly limited by the drift time of carriers moving into π-n+ junction. Using the reverse bias higher than 50 mV, the transit time across the absorber region limits the response time. The response time of small-area devices decreases in the region of week reverse bias achieving value below 1 ns.

4

Enhanced numerical analysis of current-voltage characteristics of long wavelength infrared p-on-n HgCdTe photodiodes

Jóźwikowski K., Kopytko M., Rogalski A.

Bulletin of the Polish Academy of Sciences. Technical Sciences

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2010

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Vol. 58, nr 4

523-533

EN

An enhanced original computer programme is applied to explain in detail the current-voltage characteristics of p-on-n long wavelength infrared (LWIR) HgCdTe photodiodes. The computer programme solves the system of non-linear continuity equations for carriers and Poisson equations. In the model ideal diode diffusion, generation-recombination, band-to-band tunnelling, trap-assisted tunnelling, and impact ionization are included as potential limiting mechanisms in the photodiodes. It is a clearly explained influence of extrinsic doping of an active device region on dark current-voltage characteristics and on R0A product of HgCdTe photodiodes in a wide region of temperature and wavelengths. Special attention is directed to the dependence of tunnelling probability on the shape of potential barrier within the depletion region. The theoretical predictions are compared with experimental data of high quantity photodiodes published in the available literature.

5

Two-colour HgCdTe infrared detectors operating above 200 K

Rutkowski J., Madejczyk P., Piotrowski A., Gawron W., Jóźwikowski K., Rogalski A.

Opto-Electronics Review

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2008

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Vol. 16, No. 3

321-327

EN

The performance of dual waveband HgCdTe photodiodes fabricated using metaloorganic chemical vapour deposition operated at high temperatures is presented. The effect of additional separating layer on the quantum efficiency and cross-talk of the photodiodes is analyzed. The photodiodes with cutoff wavelengths up to 6 um, good RoA product, and high quantum efficiency at 200 K have been demonstrated. The temperature dependence of the differential resistance is discussed. It is shown that the multilayer heterojunction P-n-N-n-P structure operating in a simultaneous mode has better performance than a structure operating in a sequential mode.

6

Numerical analysis of three-colour HgCdTe detectors

Jóźwikowski K., Rogalski A.

Opto-Electronics Review

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2007

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Vol. 15, No. 4

215-222

EN

The performance of three-colour HgCdTe photovoltaic heterostructure detector is examined theoretically. In comparison with two-colour detectors with two back-to-back junctions, three-colour structure contains an absorber of intermediate wavelength placed between two junctions and electronic barriers are used to isolate this intermediate region. This structure was first proposed by British workers. Three-detector structures with different localizations of separating barriers are analyzed. The calculation results are presented in the form of spatial distributions of bandgap energy and quantum efficiency. Enhanced original computer programs are applied to solve the system of non-linear continuity equations for carriers and Poisson equations. In addition, the numerical analysis includes the dependence of absorption coefficient on Burstein effect as well as interference effects in heterostructure with metallic electrical contacts. It is shown that the performance of the detector is critically dependent on the barrier's doping level and position in relation to the junction. This behaviour is serious disadvantage of the considered three-colour detector. A small shift of the barier location and doping level causes serious changes in spectral responsivity.

7

Generation-recombination effects in high temperature HgCdTe heterostructure photodiodes

Jóźwikowska A., Jóźwikowski K., Rutkowski J., Orman Z., Rogalski A.

Opto-Electronics Review

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2004

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Vol. 12, No. 4

417-428

EN

The effect of built-in electric fields and misfit dislocations on dark currents in high temperature MOCVD HgCdTe infrared heterostructure photodiodes has been investigated. From experimental data results that the current-voltage characteristics at 240 K and 300 K indicate significant contributions from tunnelling effects, which dominate the leakage current mechanism for reverse bias greater than a few tens of milivolts. Standard theoretical models show that Auger generation-recombination processes determine dark current in high temperature HgCdTe photodiodes. But taking into account only Auger mechanisms much overestimated theoretical results are obtained. To explain this fact, a two-dimensional model has been developed to investigate the dark current mechanisms in the vicinity of the junction termination at built-in electric fields. Calculated profiles of the energy bands and electric field along different cross-sections of the photodiode indicate that the electric field achieves a maximum value of the order of mid 10⁵ V/cm in the area the junction termination at the HgCdTe heterointerface. In these regions the high density of misfit dislocations are observed too. The presence of high electric field in this area decreases the ionisation energies of trap levels located in region of dislocations core, and hence increases the efficiency of Shockley-Read-Hall generation-recombination process. In addition to diffusion, generation-recombination and trap assisted tunnelling mechanisms, our model include the Poole-Frankel and phonon-trap assisted tunnelling effects in calculations of dynamic resistance of the junctions. The best fit of experimental data with theoretical predictions for dynamic resistance versus temperature has been obtained for dislocation density in the bulk of HgCdTe layer equal to 5x10⁻⁷ cm⁻².

8

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.

9

The influence of disolations on generation-recombination processes in narrow-bandgap semiconductors

Jóźwikowski K., Niedziela T.

Electron Technology

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2000

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Vol. 33, No. 4

518-528

EN

A simple model of dislocations as cylindrical regions limited with a surface at which recombination occurs is proposed. It is assumed that both the radius of the dislocation surface and the rate of surface recombination are parameters experimentally determinable. Relations for the rates of carrier recombination and generation depemding on the density of dislocations have been obtained. An iterave scheme for the system of charge-carriers transport equations to analyse photoelectric effects in narrow-bandgap semiconductors of strong inhomogeneities is presented.

10

The analysis of detection capabilities of cooled (T = 80 K) two-colour (Cd,Hg)Te photodiodes

Jóźwikowski K., Niedziela T.

Electron Technology

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2000

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Vol. 33, No. 4

529-534

EN

Properties of cooled (T= 80 K) two-colour (Cd,Hg)Te photodiodes operating simultaneously in two spectral regions (3 ÷ 4 um and 4 ÷ 8 µm) are analysed numerically. The resu;lts of coputations obtained are compared with parameters of two-colour photodiodes produced by the best Western films. Full usefulness of the programs applied for designing complex photoelectric devices is proved.

11

Some comments about carrier concentration in doped (Cd,Hg)Te structures

Jóźwikowski K., Niedziela T.

Electron Technology

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2000

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Vol. 33, No. 4

535-541

EN

A simple method for comutation of carrier concentration in doped (Cd,Hg)Te (MCT) structures is proposed. The method is based on the postulate on the existence of dopant bands. The paper is of speculative character since the dopant bands are characterized by two parameters only (the mean energy of the band and the effective density of states). These parameters are taken so as good consistency could be obtained with experimental data comprising a wide range of doping levels for various kinds of dopants.

12

Analysis of detectin parameters of non-cooled long-wavelength multi-junction (Cd,Hg)Te photodiodes

Jóźwikowski K., Niedziela T.

Electron Technology

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2000

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Vol. 33, No. 3

473-477

EN

A numerical analysis of long-wavelenght multi-junction photodiodes constructed on the basis of CdxHg1-xTe heterostructures is performed. An original iterative scheme is applied to solve the nonlinear system of continuity equations and the Poisson equation. All quantities are expressed as a function of electric potential and quasi Fermi levels. Results of computations are presented in the form of maps and plots illustrating spatial distributions of responsivity and generation-recombination noises. Such an illustration enables to explain the effect of reverse sign of the photo-voltage occurring in photoelectric devices being manufactured.

13

Nierównowagowe, chłodzone termoelektrycznie fotodiody z InAs₁₋xSbx

Jóźwikowski K., Larkowski W., Jóźwikowska A.

Biuletyn Wojskowej Akademii Technicznej

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2000

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Vol. 49, nr 2

41-52

PL

W pracy obliczono numerycznie parametry użytkowe fotodiod z InAs₁₋xSbx, w których wykorzystano zjawiska nierównowagowe zachodzące w otoczeniu skokowych złącz p-n i l-h. Pokazano, że stosując heterostrukturę można zwiększyć czułość napięciową fotodiody na skutek zwiększenia rezystancji dynamicznej. Z obliczeń wynika, że stosunkowo niewielka polaryzacja fotodiod w kierunku zaporowym powoduje znaczący wzrost ich rezystancji dynamicznej i w mniejszym stopniu zwiększenie wydajności kwantowej. Obliczenia przeprowadzono dla fotodiod na zakres widmowy 3 ÷ 5,5 μm pracujących w temperaturze 230 K.

EN

In InAs₁₋xSbx photodiode parameters have been numerically determined. Nonequilibrium effects occurring in the vicinity of p-n and l-h abrupt junctions were included. It was found that using a heterostructure the voltage responsivity of the photodiode can be enhanced. The dynamical resistance increase was responsible for that. From the calculations it follows that the respective small polarization of the photodiode in the reverse direction causes a significant increase in the dynamical resistance but there was found the increase in the quantum yield to be smaller. The calculation was carried out for photodiodes designed for 3 to 5.5 μm spectral range at temperature 230 K.

14

High-temperature InAs1-xSbx photodiodes employing nonequilibrium effects

Jóźwikowski K., Niedziela T.

Electron Technology

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1999

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Vol. 32, No. 4

378-383

EN

We determine operational parameters of high temperature (T = 230 K) InAs1-xSbx photodiodes in which nonequilibrium effects occurring near the p-n and l-h abrupt junctions are employed. It is proved that one can enhance the voltage responsivity o f a photodiode by using a heterostructure, thanks to an increase in the dynamic resistance. It is illustrated that relatively small reverse bias of photodiodes makes a considerable increase in their dynamic resistance and an increase in the quantum efficiency. The calculations are performed for photodiodes for the region o f medium infrared (3 ÷ 5.5 µm).

15

A method for analysis of spatial distribution of electrostatic potential and band structure in (Hg,Cd)Te diode heterostructures

Jóźwikowski K., Niedziela T.

Electron Technology

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1999

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Vol. 32, No. 4

384-389

EN

A method for solving the Poisson equation in strongly heterogeneous semiconductor structures is presented. It enables calculation of the spatial distribution of electrostatic potential, space-charge density, and band structure. The knowledge of spatial distributions of these quantities has practical significance in, for instance, designing of photoelectric devices employing nonequilibrium effects. The results obtained are the basis for further analysis and calculations of parameters of photoelectric diode structures applied in detection of infrared radiation. The method presented enables investigation of the influence of doping and molar-composition gradient on formation of junctions in the photodiodes designed, as well as indicates a method for limiting the unfavourable influence of misfit dislocations and surface recombination by applying internal forces occurring in regions of broadening energy gap. The combination of influence of heterogeneity of composition and doping can induce variations in electrostatic potential stronger than in homogeneous diodes, thus can enhance photovoltaic effect in detectors under construction.

16

Schemat iteracyjny dla rozwiązywania równań transportu w wąskoprzerwowych strukturach półprzewodnikowych o silnych niejednorodnościach. Przypadek stacjonarny i jednowymiarowy

Jóźwikowski K.

Biuletyn Wojskowej Akademii Technicznej

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1998

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Vol. 47, nr 7-8

161-185

PL

W pracy zaprezentowano schemat interacyjny dla rozwiązywania układu równań transportu w strukturach półprzewodnikowych o silnych niejednorodnościach. Linearyzację równań przeprowadzono metodą Newtona. Prezentowana metoda numeryczna może być zastosowana dla obliczania parametrów fotoelektrycznych przyrządów półprzewodnikowych wykorzystujących zjawiska nierównowagowe, zachodzące w miejscach silnych niejednorodności (w heterostrukturach, złączach p-n, złączach l-h i obszarach zmiany przerwy energetycznej). Dla jej zilustrowania zaprezentowano obliczenia przestrzennych rozkładów koncentracji nośników, potencjału elektrostatycznego, struktury pasmowej i charakterystyki prądowo-napięciowej w wybranych strukturach półprzewodnikowych z (InA)Sb. Obliczenia wykonano dla geometrii jednowymiarowej.

EN

It is presented an iteration scheme for solution of transport equations in narrow-band semiconductor structures with strong inhomogenities. The Newton method for linearization is applied. The numerical method can be applied for calculation of photoelectric parameters of semiconductor devices using nonequilibrium effects occurring in strong inhomogeneous regions (in heterostructures, p-n and l-h junctions and in the band-graded regions). The method is illustrated by presenting the results of spatial calculation of distribution of charge carries concentration, electrostatic potential, the band structure and current-voltage characteristics of the selected semiconductor structures with (InAs)Sb. The one dimensional case is considered.