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Home Material Sciences Compact Highly Sensitive Detectors Of Optical Radiation Based On Two-Dimensional Macroporous Silicon Structures

Compact Highly Sensitive Detectors Of Optical Radiation Based On Two-Dimensional Macroporous Silicon Structures

Description

Research into photonic crystals, a new class of composite materials, has been traditionally directed towards optical and microwave applications. The unique features of the two-dimensional macroporous silicon inspired research into a new application, highly sensitive uncooled thermal and photodetectors. Macroporous silicon structures are created by light-assisted electrochemical pore etching in silicon plates. The developed method is capable to electrochemically tune the macropore diameters and to chemically modify the surface. Produced material has cylindrical pores of 0.5 10 microns diameter and a high ratio of the depth to diameter. Effect of increase in absorption of electromagnetic radiation 102 times in comparison with the homogeneous material at λ ≤ 15 microns was measured in macroporous silicon. Relevant enhancement of photoconductivity was 30 times for periodical structures and 10 times for structures with arbitrary pore distribution due to surface wave (surface polariton) and build-in electrical field on macropore surface. Addition photoresponse maxima were measured spectral area of a surface, C H, Si H bond absorbtion (2 - 4 microns) and at short-wave region (0.56 micron). Importance of the given development will consist in creation of compact highly sensitive detectors of optical radiation for most actual from the applied point of view spectrum range 0.5 14 microns with low power consumption at room temperature.

Innovative Aspect and Main Advantages

Cheap electrochemical procedure makes lowest, simplest to use uncooled photodetectors using the integral scheme technologies, plasmochemical and photoelectrochemical etching. Our silicon based devices are suitable for analog/digital applications. Detectivity of thermal elements based on two-dimensional photonic silicon structures D* ~ 2·109 сm·Hz1/2W-1 is higher in comparison with analogues due to the greater optical absorption and lower noise level. Thus, optical absorption 98% is much higher apparently thermal detecting structures based on amorphous and polycrystalline silicon (about 80%). The noise level for macroporous silicon structures 2.5·10-9 V·Hz1/2 is determined by Johnson noise, that is the order value lower of noise in amorphous and polycrystalline silicon. Thermal coefficient 3%/deg and sensitivity of thermal detecting element based on photonic silicon structures 103 W/K are much better, than in analogues. Photodetector can be prepared on barrier structure “In–macroporous silicon” with responsivity 3 A/W and detectivity D*j= 5·1010 W 1cm·Hz1/2 for J~ 0.5-1 microns that corresponded to best PIN photodiode parameters.

Areas of Application

Devices on the base of two-dimensional photonic macroporous silicon structures meet a variety applications in view of the integrated nanophotonic circuit. Photosensitivity and surface wave formation inspired development of active and passive elements in photonic crystal microchips. In range 0.5 14 microns photodetectors efficiently operate at bad weather and in a dusty atmosphere, flexibly react on natural instability of an atmosphere. Uncooled thermal and photodetectors based on macroporous silicon structures can be used for needs of ecological monitoring of an environment (smog photosensors), building temperature control (thermovision systems) as well as the control over medicine, productions in the industry.


Fig. 1 Microphotos of two-dimensional macroporous silicon structures with the periodical (2, 6 microns) and
arbitrary (3 microns) cylinder pore distribution.


Fig. 2a. Absorbtion spectra of two macroporous silicon structures (1, 2) and monocystalline silicon.
Fig. 2b. 500 micron thermodetector test structure with macroporous silicon layer and Al contacts.


Fig. 3a.  Enhanced photoconductivity signal versus distance between macropores.
Fig. 3b. 400 micron photoreceiver sendvich structure with macroporous silicon layer and Al contacts.

Stage of Development

Thermal detector are protected by UA Patent declaration “Uncooled Thermoreceiver Element for Bolometers” No. a 2005 11998 Prototypes of uncooled thermal and photodetectors based on macroporous silicon structures available for testing were fabricated and investigated.

Contact Details

Contact person: Lyudmyla Karachevtseva V.
Lashkariov Institute of Semiconductor Physics NAS of Ukraine.
Address: Kiev-028, 41 Nauki Av.,
Tel: (380-44) 525-9815
Fax: (380-44) 525-8342
E-mail: This e-mail address is being protected from spambots. You need JavaScript enabled to view it

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