EP0913003A1 - Dispositif a semi-conducteurs a avalanche, comprenant une couche a croissance epitaxiale - Google Patents

Dispositif a semi-conducteurs a avalanche, comprenant une couche a croissance epitaxiale

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Publication number
EP0913003A1
EP0913003A1 EP97933308A EP97933308A EP0913003A1 EP 0913003 A1 EP0913003 A1 EP 0913003A1 EP 97933308 A EP97933308 A EP 97933308A EP 97933308 A EP97933308 A EP 97933308A EP 0913003 A1 EP0913003 A1 EP 0913003A1
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EP
European Patent Office
Prior art keywords
layer
avalanche
region
silicon semiconductor
doping
Prior art date
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Withdrawn
Application number
EP97933308A
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German (de)
English (en)
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EP0913003A4 (fr
Inventor
Leon Leslie Jostad
Joseph Charles Boisvert
John Thomas Montroy
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Advanced Photonix Inc
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Advanced Photonix Inc
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Publication of EP0913003A1 publication Critical patent/EP0913003A1/fr
Publication of EP0913003A4 publication Critical patent/EP0913003A4/fr
Withdrawn legal-status Critical Current

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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
    • H01L31/00—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
    • H01L31/08—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors
    • H01L31/10—Semiconductor devices sensitive to infrared radiation, light, electromagnetic radiation of shorter wavelength or corpuscular radiation and specially adapted either for the conversion of the energy of such radiation into electrical energy or for the control of electrical energy by such radiation; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof in which radiation controls flow of current through the device, e.g. photoresistors characterised by potential barriers, e.g. phototransistors
    • H01L31/101—Devices sensitive to infrared, visible or ultraviolet radiation
    • H01L31/102—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier
    • H01L31/107—Devices sensitive to infrared, visible or ultraviolet radiation characterised by only one potential barrier the potential barrier working in avalanche mode, e.g. avalanche photodiodes

Definitions

  • the present invention relates to semiconductor avalanche devices and, in particular, concerns an avalanche photodiode device that has two layers of semiconductor material that form a p-n junction wherein an avalanche of charge carriers is produced when the diode is reverse biased in response to generation of one or more charge carriers in one of the layers wherein one of the layers is grown using epitaxial growth techniques.
  • Avalanche semiconductor devices are devices that are comprised of two layers of semiconductor material that are positioned adjacent one another so that an electric field and a depletion region is formed at the interface between the two layers.
  • One such device is an avalanche photodiode (APD) which is typically comprised of a p-n junction that is reversed biased by an applied voltage so that when a photon impinges on a first layer of the avalanche photodiode and is absorbed, a charge carrier is produced in the first layer and the electric field moves the charge carrier towards the interface.
  • the first layer is configured so that an avalanche of charge carriers are generated in response to the charge carrier produced as a result of the absorption of the photon travelling towards the interface.
  • LAAPD large area avalanche photodiode
  • LAAPD devices are available that have surface areas in excess of 20 mm 2 . It is desirable that over the entire surface area of the APD, that the electrical signal produced by the device is substantially uniform regardless of where the photon impinges on the device.
  • gain uniformity is a function of the doping profile of the layer of the APD that receives the photons.
  • doping inconsistencies within this layer can result in the electric field between the layers varying from region to region within the APD. These variations in the electric field can further result in fewer or greater charge carriers being produced by different regions of the device in response to a photon impinging upon the region of the layer containing the doping inconsistencies.
  • the p-n junctions which form the APD devices are fabricated by diffusing a p- doped region into an n-doped substrate using well-known diffusion techniques.
  • One difficulty with the well-known diffusion techniques used in producing APD's is that there is often disuniformity of the doping profile. Consequently, prior art APD's suffer from non-uniformity of gain across the surface area of the APD. This non-uniformity of gain is exacerbated in LAAPD devices.
  • a further difficulty that results from forming p-n junctions for APD devices using diffusion techniques is that the interface between the p-region and the n-region is generally diffuse.
  • the exact position of the interface over the entire surface area of the APD varies across the surface area of the interface.
  • the p-dopant will have diffused farther into the n-substrate than in other regions. Consequently, in some regions of the APD, the avalanching of charge carriers will occur at a region that is farther from the p-n interface than in other regions. This results in a reduction of gain uniformity and also produces an increase in the noise of the circuit.
  • the diffuse interface between the p and the n region produces a less sensitive APD and this problem is exacerbated in large area avalanche photodiode applications (LAAPD).
  • LAAPD large area avalanche photodiode applications
  • Quantum efficiency is defined as the ratio of electron hole pairs that is created in a region of an APD to the number of photons that are incident on the region. It will, of course, be appreciated that increased quantum efficiency results in more sensitive APD devices. It is understood that the quantum efficiency of a semiconductor is dependent upon several factors, one being the characteristic absorption depth of the photons impinging upon the device.
  • the characteristic absorption depth is much greater than the typical thickness of the p-region which receives the photons in an APD device.
  • APD device many APD devices have a p-layer that is on the order of 30 microns wherein the characteristic absorption depth of a photon having a wavelength of 1.06 microns is on the order of 770 microns.
  • the thickness of the p-layer is so small when compared to the characteristic absorption depth, the percentage of photons that are absorbed to form electron hole pairs that will ultimately avalanche is small.
  • the doping of the layer at any given depth is typically cross-sectionally non- uniform across the layer. Increasing the thickness of the region containing this doping results in more non-uniformity and less uniform gain across the device due to increased probability of avalanching occurring at different distances from the interface.
  • an APD device and a process for manufacturing the same that has improved uniformity of doping characteristic at any cross-section to the junction formed by the interface between the p and the n regions of the semiconductor material comprising the APD, as well as a precise uniform junction that does not vary in its depth.
  • an APD device that has improved quantum efficiency and is therefore more sensitive that still maintains a high degree of gain uniformity and low noise characteristics.
  • the avalanche photodiode device of the present invention which comprises a first semiconductor layer having a first doping characteristic and a first crystal structure and defining a first surface and a second semiconductor layer deposited on the first semiconductor layer so that the second semiconductor layer forms an interface with the first layer at the first surface and extends outward therefrom.
  • the second semiconductor layer has a second doping characteristic and the first crystal structure and defines an outer surface. Further, when the second layer is positioned on the first layer, a depletion region is formed at the interface between the layers so that when the junction between the layers is reversed biased, an avalanche of charge carriers is produced in response to a photon penetrating into the device.
  • the first semiconductor layer is comprised of a substrate of n-type silicon and the second semiconductor layer is comprised of a layer of p-type silicon that is epitaxially grown using chemical vapor deposition techniques on the n-type substrate.
  • an improvement in the uniformity of doping characteristics of the p-type silicon region can be achieved which can result in improved gain uniformity for the device.
  • the devices of the preferred embodiment have an avalanching layer that is formed using epitaxial growth processes. This allows for tailoring the characteristics of the avalanching layer so as to optimize the performance characteristics of the device.
  • the avalanching layer can be optimized so that the avalanching layer achieves a high current gain in response to a photon impinging on the avalanching region while still maintaining a high degree of gain uniformity.
  • the use of epitaxial growth processes to form the avalanching layer allows for modifications of the avalanching layer to obtain desired performance characteristics.
  • the second layer of the avalanche photodiode has a doping profile wherein a region of the second layer that is located a first distance from the interface between the first and second layers has a first doping concentration and a region of the second layer that is located a second distance from the interface between the first and second layers has a second doping concentration.
  • the first doping concentration is greater than the second doping concentration and the first distance is less than the second distance.
  • the epitaxially grown p-layer is the avalanching layer and it has a region of increased doping concentration that is located adjacent to the interface between the p and the n layers. It will be appreciated that using chemical vapor deposition epitaxial growth techniques, buried layers of increased doping concentration can be positioned within a region of an avalanching layer that receives photons.
  • one application of this aspect of the invention is that a uniform region having a high doping concentration that is selected to provide a particular gain characteristic for the device can be grown in the region and then a thicker spectral absorption region having a lower doping concentration can then be grown using the epitaxially growth techniques.
  • This can be used to form an avalanche photodiode that has an avalanche layer having a thick spectral absorption region and a more highly doped buried gain region positioned adjacent the interface.
  • the thicker spectral absorption region increases the quantum efficiency of the APD and therefore makes the device more sensitive.
  • the buried gain region maintains a desired current gain for the device without sacrificing gain uniformity.
  • a thinner buried gain region can be grown with a thicker lightly doped spectral absorption layer positioned between the light receiving surface and the buried gain region.
  • Another aspect of the present invention is that a process is provided wherein the doping profile of one of the layers of the avalanche device can be tailored to achieve particular performance characteristics. Specifically, using chemical vapor deposition epitaxial layer growth, different regions of the layer can be grown to have particular doping concentrations that will result in particular performance characteristics.
  • the process comprises growing an epitaxial layer that has a doping profile such that there is a region that has a dopant concentration of 1 x 10' 6 dopant atoms per cubic centimeter that is on the order of 7 microns thick and is positioned immediately adjacent the interface.
  • the layer also includes a second region having a dopant concentration of approximately 5 x 10" dopant atoms per cubic centimeter wherein the second region is positioned on the surface of the first region that is located distal from the interface and is approximately 100 microns thick.
  • the present invention provides an avalanche device that has improved performance characteristics.
  • the device has improved uniformity of gain and lower noise characteristics.
  • the process of fabricating the device of the present invention allows for great flexibility in configuring the layer of the device to achieve particular performance characteristics.
  • Figure 1A is a schematic illustration of a first embodiment of a bevelled edge avalanche photodiode having a first layer and a second layer extending outward therefrom wherein the second layer is formed using epitaxial growth techniques;
  • Figure 1B is a graph illustrating the doping profile of the device of Figure 1A
  • Figure 2A is a schematic illustration of a second embodiment of a bevelled edge avalanche photodiode wherein the avalanche photodiode includes a first layer of semiconductor material and a second layer of semiconductor material and wherein the second layer is formed using epitaxial growth techniques so that it has a region of higher doping concentration immediately adjacent an interface between the first and second layers
  • Figure 2B is a graph which illustrates the doping profile of the device of Figure 2A
  • Figure 3A is a schematic illustration of a third embodiment of a bevelled edge avalanche photodiode device having a first layer and a second layer positioned thereon to form an interface wherein the second layer is formed using epitaxial growth techniques so that it has a region of increased doping concentration that is positioned within the second layer at a position that is spaced from the interface; and
  • Figure 3B is a chart illustrating the doping profile of the device of Figure 3A.
  • FIG. 1A illustrates a first embodiment of an avalanche photodiode 10 that is prepared using a unique fabrication technique.
  • Figure 1A shows a first semiconductor layer 12 which is comprised in this embodiment of an n-type single crystal silicon substrate having resistivity of typically 60 to 90 ohm cm.
  • the substrate 12 defines a first surface 14.
  • a second semiconductor layer 16, which in this embodiment comprises an avalanching layer, is formed on the first surface 14 of the substrate 12 so that the first surface 14 defines an interface between the substrate
  • the avalanche layer 16 is the layer where the majority of an avalanche of charge carriers will be produced in response to one or more photons impinging upon the device 10. It will be appreciated, however, that a small amount of charge carriers will be produced by avalanche in other regions of the device 10 including the substrate 12.
  • the avalanche layer 16 is comprised of a p-type single crystal surface layer that is epitaxially grown on the n-type single crystal substrate 12 in a manner that will be described in greater detail hereinbelow.
  • the avalanche layer 16 has an outer surface 19.
  • a contact layer 20 is diffused onto an outer surface 19 of the avalanche layer 16 using well-known diffusion techniques.
  • An ohmic contact 26 comprised of a thin n+ + doped silicon layer can also be formed on a bottom surface 24 of the substrate 12 through diffusion techniques.
  • Figure 1A also illustrates an electrode structure 21 formed on the upper surface 19 of the device 10.
  • the electrode structure 21 is preferably comprised of silicon and provides a contact for a voltage that is applied to the avalanche photodiode device 10. It will be appreciated that the electrode structure
  • the electrode structure 21 may also comprise a reactive metal such as molybdenum, tungsten, titanium or other contact metals such as gold, aluminum and platinum. It will also be appreciated that the electrode structure 21 is generally shaped as a ring to expose a large area of the outer surface 15 of the avalanche layer 16 to light as possible. It is understood that positioning the p-type avalanche layer 16 on the n-type substrate 12 will result in a depletion region 25 (represented by dashed lines in Figure 1A) being formed in the substrate 12 and the avalanche layer 16, when a biasing voltage is applied between the electrode structure 21 and the contact 26.
  • a depletion region 25 represented by dashed lines in Figure 1A
  • the doping process of the p-type layer 14 is performed so that the depletion layer extends almost to the upper surface 15 of the avalanche region 16.
  • Figure 1A also illustrates that the avalanche photodiode 10 has bevelled side surfaces 28a and 28b that are bevelled so that when a biasing voltage is applied between the electrode structure 21 and the contact 26, the strength of the electric field at the edge of the device 10 does not exceed the strength of the electric field within the device 10 in a manner that is known in the art.
  • the avalanche photodiode device 10 is circular in configuration and the bevelled edges 28a and 28b extend around the entire outer circumference of the device 10.
  • Figure IB shows the dopant profile of the avalanche photodiode 10 of Figure 1A in greater detail.
  • the avalanche layer 16 is comprised of a layer of p-type material that has a dopant concentration of approximately 2 x 10' 5 dopant atoms per cm 3 and has a thickness of approximately 12 microns.
  • Figure 1B also illustrates that the n-type substrate 12 in this preferred embodiment has a dopant concentration of approximately 1 x 10" dopant atoms per cm 3 and is greater than approximately 300 microns thick.
  • Figure 1B also illustrates that the contact region 20 which has a dopant density of approximately 1 x 10 1 ⁇ dopant atoms per cm 3 and is approximately 0.2 microns thick.
  • the n-contact 24 has a dopant concentration of approximately 1 x 10 20 dopant atoms per cm 3 and is approximately 0.2 microns thick.
  • the dopant profile of the avalanche layer 16 is such that there is a very sharp or abrupt interface between the p-doped avalanche layer 16 and the n-doped substrate 12.
  • the interface between the p and the n layers is very abrupt in that the layer of p-doped silicon essentially begins at the outer surface 14 of the n-doped substrate 12 so that the p- doped region 14 has the same crystalline structure as the n-doped region 12.
  • a reverse biased voltage is applied between the electrode structure 21 and the contact 26 that is between approximately 1000-3000 volts. Consequently, when a photon enters the avalanche layer 16 through the contact layer 20, an electron hole pair is preferably formed within the undepleted region and then diffuses to the depletion region 25 and a minority charge carrier, i.e., electrons in this embodiment, is then swept towards the interface 14 by the electric field created by the applied reverse bias voltage.
  • a minority charge carrier i.e., electrons in this embodiment
  • the device 10 preferably exhibits a current gain on the order of 200.
  • the avalanche of charge carriers results in a measurable electrical signal in response to the photon impinging upon the avalanche layer 16.
  • the avalanche layer 16 has a uniform dopant profile as a result of the growth of the avalanche layer 16 using CVD epitaxial growth techniques, that there is a very high degree of spatial uniformity of the dopant atoms within the avalanche layer 16. This results in a high degree of uniformity of the current gain resulting from the avalanching process. Further, the epitaxial growth process also results in an absence of crystalline processing defects. For example, using the process described herein an APD having a gain of 300 and an area of more than 40 mm 2 had a gain uniformity of 3% as compared to 5% for comparable prior art devices.
  • the p-region 16 is preferably grown using a chemical vapor deposition epitaxial growth process.
  • a graphite susceptor that provides mechanical support for the wafer and to transfer thermal energy to the wafers.
  • the wafers are processed sequentially, wherein they are placed one at a time on the susceptor in a cassette to cassette process.
  • the susceptor Prior to epitaxial deposition, the susceptor must be passivated.
  • the passivation process comprises an in situ gas phase etching of the susceptor surface by using a mixture of HCI (etchant gas) and H 2 (carrier gas) containing H 2 + HCI at about 1 90°C for 5-7 minutes.
  • the etch is typically followed by a CVD process wherein a silicon source gas is flowed through the chamber in combination with a hydrogen carrier gas.
  • a typical silicon source gas such as trichlorosilane (SiHCLj) thermally reacts at the surface of the susceptor causing deposition of silicon.
  • the resulting deposition passivates the susceptor surface and prevents potential contamination of the silicon wafers during the subsequent epitaxial growth process.
  • an n-type silicon wafer is placed on the susceptor in the CVD chamber in a manner that is known in the art and the wafer is preheated in the H 2 carrier gas at approximately 1150°C for three minutes to remove any remaining nascent oxide from the surface of the silicon wafers.
  • the p-type avalanche layer 16 is then deposited using chemical vapor deposition by flowing a typical gas combination of a silicon source gas such as trichlorosilane (SiHCI 3 at 0.18 standard liters per minute), a p-type dopant gas such as diborane (B 2 H ⁇ ) at 0.18 standard liters per minute and a carrier gas such as hydrogen (H j ) at 48 standard liters per minute through the CVD epitaxial chamber at temperatures of between 1100 and 1200 C at approximately atmospheric pressure.
  • a silicon source gas such as trichlorosilane (SiHCI 3 at 0.18 standard liters per minute
  • a p-type dopant gas such as diborane (B 2 H ⁇ ) at 0.18 standard liters per minute
  • a carrier gas such as hydrogen (H j ) at 48 standard liters per minute
  • the p-type dopant gas in the CVD chamber is diluted to provide the doping concentration that is desired for the avalanche layer 16 which, in the embodiment shown in Figure 1, is 2 x 10 *5 dopant atoms per cm 3 .
  • the utilization of a rectangular shaped shower head gas injection system provides planar flow of the reactant gases to the wafer surface allowing growth of highly uniform thickness epitaxial layers.
  • the use of advanced computer controlled mass flow controllers further allow precise metering of reactant gas flow resulting in extraordinary control and reproducibility of epitaxial layer doping concentration.
  • the above-described epitaxial growth procedure results in a very uniform avalanche layers 16 being grown to a desired thickness on the n-substrate 12.
  • the CVD epitaxial growth technique further allows for precise control of the dopant rate and the dopant profile within the layer 16.
  • the epitaxial growth method described hereinabove reduces the need for a commonly used post doping and annealing step that is used with diffusion and implantation based techniques for forming APD's to reduce non- uniformity and crystalline defects.
  • FIG. 2A illustrates another embodiment of an avalanche photodiode 30 having an epitaxially grown avalanche layer.
  • the avalanche photodiode 30 includes a substrate 40 which, in the preferred embodiment, is comprised of an n-doped layer that has a first surface 42.
  • a second layer of a semiconductor material 44 comprising an avalanche layer is then deposited on the surface 42 of the substrate 40 so as to define an interface at the surface 42.
  • the avalanche layer 44 is comprised of a p-doped layer of silicon wherein the p- doped layer of silicon includes a gain region 48 of heavily p-doped silicon and a more lightly doped spectral absorption region 46 of /7-doped silicon.
  • the avalanche layer 44 is epitaxially grown on the surface 42 using an epitaxial growth process similar to the process described hereinabove, except that the growth process initially results in the more heavily doped gain region 48 being grown first immediately adjacent the interface 42. Subsequently, the more lightly doped rr region 46 is then grown on top of the more heavily doped p-region 48.
  • a more heavily ⁇ + doped depletion stop layer 50 is then grown on an outer surface 45 of the ⁇ region 46 using CVD epitaxial growth techniques.
  • a p+ + doped contact surface 52 is then grown on an outer surface 51 of the p+ region 50 using known diffusion techniques.
  • An electrode structure 54 similar to the electrode structure 21 described hereinabove is then positioned on an upper photon receiving surface 53 of the device 30. Further, an electrical contact 56 is grown on a bottom surface 55 of the semiconductor substrate 40.
  • the depletion stop region which comprises a more highly doped region of semiconductor material, is positioned on the outer surface of the avalanche region so that the depletion region does not extend to the electrode structure.
  • Figure 2B illustrates the doping profile of the avalanche photodiode 30 in greater detail.
  • the substrate 40 is comprised of n-doped silicon having a dopant concentration of approximately 6 x 10" dopant atoms per cm 3 and a resistivity of 60-90 ohm cm.
  • the buried p-doped region 48 has a dopant concentration of approximately 2 x 10 15 dopant atoms per cm 3 and is approximately 10 microns thick.
  • the ⁇ region 46 has a dopant concentration of 5 x 10 12 dopant atoms per cm 3 and is approximately 100 microns thick.
  • the depletion stop layer 50 has a dopant concentration of approximately 10 18 dopant atoms per cm 3 and is approximately 5 microns thick.
  • the photon receiving surface 52 and ohmic contact 56 both have a dopant concentration of approximately 10' a dopant atoms per cm 3 and each is approximately .2 ⁇ m thick.
  • an avalanche photodiode can be produced that has a region which has a higher doping concentration located adjacent the interface 42 between the n-substrate 40 and the p-region 46.
  • the doping profile of the epitaxial grown p layer 43 can be varied to achieve different performance characteristics of the device.
  • the avalanche photodiode 30 shown in Figure 2A is configured to maximize the response to photons having a wavelength on the order of 1.06 microns. It is understood that the quantum efficiency of the device is increased when the thickness of the avalanche layer of the avalanche photodiode is increased.
  • the difficulty with increasing the avalanche layer is that the avalanche layer generally has to be of a single dopant concentration that is selected to provide the desired gain characteristics.
  • An increase of the thickness of an avalanche layer that is more highly doped to provide a desired gain characteristic can result in a device that has less gain uniformity and more noise characteristics due to avalanche occurring at different distances from the interface between the avalanche layer and the substrate as discussed above.
  • the thickness of the avalanche layer 44 includes the spectral absorption region 46 formed of more lightly doped /7-type silicon.
  • the thickness of the avalanche layer 44 is increased while reducing the effects of avalanche occurring at different distances from the interface by decreasing the dopant concentration in this region.
  • the desired gain characteristic is achieved by epitaxially growing the more highly p-doped buried gain region 48 which is buried beneath the absorption layer.
  • This minority charged carrier then is swept towards the gain region 48 by the electric field that results as a result of the reverse bias and an avalanche of charged carriers is preferably produced in the relatively thin gain region 48 immediately adjacent the interface 42. Consequently, the avalanche photodiode 30 is less sensitive to avalanching occurring at different distances from the interface 42.
  • the spectral absorption layer has a low doping concentration when compared to the gain region, if photon absorption occurs at different locations within the spectral absorption region 48, there is less variation in the resulting current gain as the most significant portion of the avalanching is most likely to occur in the relatively thin gain region.
  • the depletion region preferably reaches through the ⁇ region and provides stable avalanche gain through the avalanche region.
  • the quantum efficiency of the device has also been increased.
  • the quantum efficiency is approximately 12% at 1.06 microns for carriers that undergo full amplification. This compares to a quantum efficiency for an avalanche photodiode having comparable gain characteristics formed using diffusion based techniques of less than 5%.
  • CVD epitaxial growth techniques to form buried regions of increased doping concentration can result in a device that has a greater quantum efficiency and is therefore more sensitive without any decrease in the gain or noise characteristics.
  • Figures 3A and 3B further illustrate that the doping profile of an avalanche layer of a device can be varied to achieve different performance characteristics for the device.
  • Figure 3A illustrates another embodiment of an avalanche photodiode 60 that is comprised of a substrate 70 which is preferably an n-doped substrate.
  • the substrate includes a first surface 72 wherein a second layer 74 of semiconductor material is deposited thereon so that an interface is defined at the surface 72.
  • the second layer 74 in this embodiment is comprised of p-doped silicon that is grown using CVD epitaxial growth techniques so that it has a varied dopant profile and defines an avalanche layer for the device.
  • the avalanche layer 74 includes a spacer layer 76 of lightly /7-doped material that is positioned immediately adjacent the interface 72.
  • a more heavily doped gain region 78 is then grown on an outer surface 77 of the ⁇ -doped spacer region 76 using the CVD epitaxial growth techniques described above.
  • a spectral absorption region 80 is then grown on an outer surface 79 of the gain region 78 using epitaxial growth techniques.
  • the spectral absorption region 80 is more lightly doped than the gain region 78 but increases the thickness of the avalanche layer 74 so as to improve the quantum efficiency of the device 60 in the manner described above.
  • a depletion layer stop region 82 is formed on an outer surface 81 of the spectral absorption region 80 for the same purpose that was described above.
  • a contact layer 84 of a very heavily p-doped silicon is then diffused into the depletion stop region 82 in the manner described above and an electrode structure 86 is then positioned on an upper surface 83 of the device.
  • an ohmic contact 88 is formed on a bottom surface 89 of the substrate 70 so that the electrode structure 86 and the ohmic contact 88 permit the reverse biasing voltage to be applied to the APD device.
  • the primary difference between the avalanche photodiode 60 and the avalanche photodiode 30 described above in reference to Figures 2A and 2B is that there is a 7 micron thick spacer layer 76 positioned between the gain region 78 and the interface 72. This spacer region has the effect of maintaining a substantially constant electric field (shown in dashed lines) at or near interface.
  • the operation of the device 60 is similar to the operation of the device 30 described in reference to Figures 2A and 2B and the device 60 simply illustrates that the doping profile of the second layer can be varied to achieve specific performance characteristics of the device.
  • avalanche photodiodes using the epitaxial growth process described hereinabove that has a range of noise equivalent power (NEP) of between 1.8 x 10" and 6.3 x 10 ,s watts per Hz ' for an area of greater than 20 mm 2 in response to receiving light having a wavelength of between 300 nm and 850 nm.
  • NEP noise equivalent power
  • the spatial uniformity of the dopant atoms which directly impacts the gain uniformity and the energy resolution of an avalanche photodiode is also improved in an avalanche photodiode that has a p-region formed using CVD epitaxial growth.
  • a 10 mm large area avalanche photodiode formed using the above described techniques had a 9.5% FWHM in response to a 55 Fe 5.9 keV X-ray irradiation.
  • the specification for standard 10 mm LAAPD formed through diffusion techniques is that the full width at half maximum of the ⁇ Fe distribution should be less than 18%.
  • experimental data obtained by the applicant indicates that the spatial uniformity of a p layer grown using epitaxial growth techniques of the preferred embodiment result in a p-layer that has much greater spatial uniformity and consequently greater gain uniformity and energy resolution.
  • the avalanche devices of the preferred embodiment have greater gain uniformity, less noise and greater performance characteristics than the avalanche devices of the prior art. Further, growing the p-region using CVD epitaxial growth techniques allows for greater control over the doping profile of the region which can then be used to obtain devices that have specific performance characteristics. While the embodiments of the invention have been described in terms of avalanche photodiode devices, it will be appreciated by a person skilled in the art that any avalanching device which experiences current gain as a result of generation of a charge carrier in an avalanche layer can be made using the techniques described above without departing from the spirit of the present invention.

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Abstract

L'invention concerne une diode à avalanche comprend une première couche d'un matériau semi-conducteur (12) et une deuxième couche d'un matériau semi-conducteur (18) placée au-dessus de manière à définir un interface (14). La première couche de matériau semi-conducteur (12) est un substrat et la deuxième couche (18) comprend une couche d'avalanche dans laquelle une zone de déplétion est générée au niveau de l'interface. La deuxième couche est de préférence générée à l'interface. La deuxième couche (18) est de préférence déposée sur la première couche (12) au moyen de techniques de croissance épitaxiale par dépôt chimique en phase vapeur. Lorsque des photons entrent dans la couche d'avalanche, un porteur de charge minoritaire est produit et, lorsque le dispositif est polarisé en sens inverse, une avalanche de porteurs de charges est produite dans la couche d'avalanche. Puisque la couche d'avalanche est déposée avec des techniques de croissance épitaxiale, l'uniformité de la couche entraîne une plus grande uniformité de gain. En outre, on peut configurer la couche d'avalanche avec des techniques de croissance épitaxiale pour obtenir une zone de gain à plus grande concentration de dopant, contiguë à l'interface à couche d'absorption spectrale, avec une plus faible concentration de dopant interposée entre la zone de gain et la surface qui reçoit les photons. Ainsi, on peut obtenir un meilleur rendement quantique dans un photodiode à avalanche présentant cette configuration tout en maintenant un haut degré d'uniformité de gain des caractéristiques de faible bruit.
EP97933308A 1996-07-03 1997-07-03 Dispositif a semi-conducteurs a avalanche, comprenant une couche a croissance epitaxiale Withdrawn EP0913003A4 (fr)

Applications Claiming Priority (3)

Application Number Priority Date Filing Date Title
US3534996P 1996-07-03 1996-07-03
US35349P 1996-07-03
PCT/US1997/011768 WO1998000873A1 (fr) 1996-07-03 1997-07-03 Dispositif a semi-conducteurs a avalanche, comprenant une couche a croissance epitaxiale

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EP0913003A1 true EP0913003A1 (fr) 1999-05-06
EP0913003A4 EP0913003A4 (fr) 1999-08-25

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EP (1) EP0913003A4 (fr)
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US6794631B2 (en) 2002-06-07 2004-09-21 Corning Lasertron, Inc. Three-terminal avalanche photodiode
CN108369968B (zh) * 2015-12-01 2021-07-27 夏普株式会社 雪崩光电二极管
US11101400B2 (en) * 2017-11-28 2021-08-24 Luxtera Llc Method and system for a focused field avalanche photodiode
CN108666382B (zh) * 2018-07-09 2024-03-19 长沙理工大学 Soi基lsambm雪崩光电二极管及其制备方法
CN116504856A (zh) * 2019-08-28 2023-07-28 光程研创股份有限公司 具有低暗电流的光侦测装置

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CA2259502A1 (fr) 1998-01-08
JP2001525117A (ja) 2001-12-04
WO1998000873A1 (fr) 1998-01-08
AU3652597A (en) 1998-01-21
EP0913003A4 (fr) 1999-08-25

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