Avalanche photodetector with expanded spectral recording range for optical-radiation

FIELD: recording radiation in wide range of spectrum, including ultraviolet one.

SUBSTANCE: proposed avalanche photodetector has semiconductor p-n layer and incident-radiation spectral compound converter in the form of fluorescent layer. Optically transparent layer of high refractive index is provided between incident-radiation spectral compound converter and semiconductor layer.

EFFECT: enhanced effectiveness of incident-radiation spectral compound conversion without heavy loss in photodetector sensitivity due to reduced loss brought in by fluorescent layer structure.

3 cl, 4 dwg

The invention relates to the field of microelectronics, in particular for semiconductor receivers intended for registration of radiation and charged particles.

Known semiconductor photodetector according to the patent RU, 1634065, CL H01L 31/06, 1994, with high photosensitivity in the ultraviolet region of the spectrum, which introduced an additional dielectric layer with a finite bandgap. It refers to a specific type photodetectors. In avalanche photodetector increase the sensitivity in the shortwave region of the spectrum either by increasing the number of carriers generated by incident photons in this spectral region within the region of amplification, either by reducing the limiting sensitivity of the dark currents.

Known avalanche photodetector according to the patent RU, 2185689, CL H01L 31/06, 2002, From the description of the patent, it follows that small dark current provide a small amount of semiconductor material that generates current under the action of incident photons. Reducing the thickness of the active semiconductor layer and reaching the surface of the device can significantly minimize the dark current and increase the sensitivity of the photodetector in the field of short-wave optical radiation, however, the active layer thickness is difficult technologically. To the WMD, this leads to a significant decline in the sensitivity of the photodetector in the long-wave region of the spectrum.

Known avalanche photodetector according to JP 6305077 A, CL 01L 31/10, 1998, containing semiconductor layer, the p-n junction and luminescent Converter, designed to extend the spectral range of sensitivity of the photodetector and made in the form of luminescent (fluorescent) film, localized in the region of the p-n junction. As follows from the description of a sensor, its sensitivity can be adjusted by changing the thickness of the said film. However, the sensitivity in General is lost due to losses in the conversion, due to the structure and properties of luminescent material, in particular its isotropy.

The present invention solves the problem of increasing the efficiency of conversion of the spectral composition of the incident without significant loss of sensitivity of the sensor by reducing losses caused by the peculiarities of the structure of the luminescent layers of the Converter.

The task is solved in that the avalanche photodetector comprising a semiconductor layer containing a p-n junction, and the Converter spectral composition of the incident radiation in the form of a luminescent layer between the transducer spectral composition of the incident radiation and the semiconductor layer is made of the layer of optically transparent material with high refractive index. The luminescent layer is ispolnen composite based on optically transparent polymer with the inclusion of one or more keep the attachment (i.e. absorbing the radiation in one spectral region and emit radiation of a different region of the spectrum) additives for the shift of the spectrum of incident radiation in the region of maximum sensitivity of the photodetector. On the surface of the transducer spectral composition of the incident radiation can be also applied optically transparent protective layer.

The additional layer of material with a high refractive index reduces losses during the conversion, due to the isotropy of the phosphors. Composite layer provides efficient conversion of the energy absorbed by one of the component layer, the excitation energy of the other components. It can be made on the basis of optically transparent substance, for example, a polymer included in the composition to keep the attachment additive in the form of a phosphor that absorbs light blue-violet spectral range from 200 nm to 480 nm) and emitting in the green spectral range from 450 nm to 600 nm), where the sensor has a high sensitivity. More preferred from the viewpoint of conversion efficiency and the degree of expansion of the range of spectral sensitivity is the use of several additives, successively shifting the spectrum of the short-wave region in the region of highest sensitivity of the photodetector (from 550 nm to 700 nm). The polymer can be, for example ethylene, and additives - complexed europium nitrate and metals lantanoides the poison in the form of particles of isomorphous crystals, or ferrogermanat connection with additional inclusions of phosphors based halophosphate calcium activated with antimony and manganese, are able collectively to ensure the effectiveness of the transformation of radiation up to 90%. Can be used with other fluorescent additives, the characteristics of the absorption and radiation of which meet the necessary requirements ("Polymeric film materials", Ed. Wegele, M.: Chemistry, 1976, s-105; "high-Molecular compounds", vol. B, v.37, 1995, s-527).

The invention is illustrated by the description of the exemplary embodiment of the photodetector and the attached graphics. Figure 1 presents a section of the photodetector; figure 2 - dependence of the quantum efficiency of the photodetector from the wavelength of the incident radiation with the introduced by the Converter (solid line) and without (dashed line); figure 3 and 4 absorption spectra (curves 1 and 3) and emission (curves 2 and 4) first and second fluorescent additives, respectively, was used to create the composite layer.

The photodetector includes a dielectric substrate 1, located on the substrate of the semiconductor layer 2, for example p-type conductivity containing region 3 increased, for example, n+, carrier concentration, and the layer 2 and region 3 form a p-n junction, and the electrode 4. Fluorescent transformed the spectrum Converter 5 is located over the semiconductor layer and is made in the form of the composite layer, which is based on the polymer, as amended by the first and second fluorescent additives. As additives used phosphors with the characteristics of the absorption and radiation, are shown in figure 3 and 4. One of the phosphors pereizuchit light from the blue-ultraviolet region in green (figure 3), the second - from green to red (figure 4). The optimum thickness of the composite layer is 10-50 μm. Between the semiconductor layer 2 and the Converter 5 layer 6 made of optically transparent material with high refractive index, such as a dielectric, which allows to reduce the loss due to the isotropy of the luminescent layer. To simplify the technological process of manufacturing the photodetector mentioned optically transparent material with high refractive index can be used as a basis when creating the composite layer. On the surface of the transducer may be applied optically transparent protective layer 7.

Avalanche photodetector operates as follows.

Field-electrode applied voltage necessary to create in a semiconductor layer containing a p-n junction, the space charge region (SCR) with a field strength sufficient for avalanche amplification of carriers generated under the action of photons penetrating the semiconductor layer. The radiation incident on the photodetector, is undergoing in the Converter changing spectral composition. Radiated towards the surface of the semiconductor layer, the photons are converted spectrum are absorbed by the SCR, generate current carriers that avalanche breed, which leads to the internal amplification of the photocurrent. Thus, the conversion of photon energy short-wave part of the spectrum in the energy of the photons that part of the spectrum, where the sensitivity of the photodetector, the most high, increase the number of carriers trapped in the scope of the current amplification, thus improving the sensitivity of the photodetector in the shortwave region of the spectrum several times without loss of sensitivity in the remaining part of the spectrum of the incident radiation, which is confirmed experimentally defined dependency of the quantum efficiency of the photodetector as a function of wavelength, are presented in figure 2.

The photodetector according to the present invention can be used for registration of radiation in a wide spectral range, including in the area of deep ultraviolet radiation.

1. Avalanche photodetector comprising a semiconductor layer containing a p-n transition and the Converter spectral composition of the incident radiation in the form of a luminescent layer, characterized in that between the transducer spectral composition is and the incident radiation and the semiconductor layer is made of the layer of optically transparent material with high refractive index.

2. Avalanche photodetector according to claim 1, characterized in that the luminescent layer is made of a composite based on the optically transparent polymer with the inclusion of one or more additives keep the attachment for the shift of the spectrum of incident radiation in the region of maximum sensitivity of the photodetector.

3. Avalanche photodetector according to claim 1, characterized in that the surface of the transducer spectral composition of the incident radiation caused optically transparent protective layer.