WO2009106032A1

WO2009106032A1 - Radiation-receiving semiconductor component and method for operating the semiconductor component

Info

Publication number: WO2009106032A1
Application number: PCT/DE2009/000157
Authority: WO
Inventors: Ignaz Eisele; Ulrich Abelein
Original assignee: Ketek Gmbh
Priority date: 2008-02-27
Filing date: 2009-02-05
Publication date: 2009-09-03
Also published as: DE102008011280A1; DE102008011280B4

Abstract

A radiation-receiving semiconductor component (1) having a semiconductor body (2) and a radiation inlet side (3) is provided, wherein the semiconductor body comprises a detection region (7) provided for radiation reception, at least two electrical contact regions (4, 5), and at least one doped barrier region (8), a current path (6) extending between the contact regions in the semiconductor body, the barrier region and the detection region being disposed in the current path between the contact regions, and the barrier region being suitable for configuring a potential barrier, which is disposed between the detection region and that contact region which is located on the side of the barrier region facing away from the detection region, as viewed along the current path.

Description

description

A radiation-receiving semiconductor component and method for operating the semiconductor component

The invention relates to a radiation receiving the semiconductor device and a method for operating the semiconductor device.

For radiation detectors based on semiconductors, for example, avalanche photodiodes can be used as semiconductor components (English: Avalanche Photo Diode, in short: APD). As an avalanche photodiode is suitable, for example, a reverse biased pin diode. The operating voltage (blocking voltage) of the diode is chosen so that the diode goes into the state of avalanche breakdown when a single electron-hole pair in the intrinsic (i) zone occurs. By avalanche multiplication of the electrons and holes in the breakdown state, a significant measurable signal can be obtained to which both the electrons and the holes contribute. Achieving the breakdown state typically requires high field strengths, for example of 10 ⁵ V / cm or more, and thus high reverse voltages, for example of 100 V or more.

At constant operating voltage, the diode remains in the breakdown state. In order to bring the diode back into the initial state-that is, the non-broken state-and thus make the diode ready again for further radiation detection, a high-impedance resistor can be connected in series with the diode. The avalanche current can flow away via the resistor. Of the Voltage drop across the resistor leads to a reduction in the voltage across the diode (so-called quenching). Due to the voltage drop across the resistor, the field strength in the diode drops below the value required for avalanche breakdown. The current flowing through the diode will dry up in the sequence.

In APD, electron-hole pairs generated thermally or through tunneling effects, such as band-to-band tunneling, can also trigger avalanche breakdown. Thus, the diode can deliver a signal without any incident of a photon to be detected.

An object to be solved is to specify an improved radiation reception of the semiconductor component and a method for operating this component.

This object is achieved, for example, by the subject matter of the independent claims. Advantageous embodiments and further developments are the subject of the dependent claims.

According to one embodiment, a radiation reception of the semiconductor component has a semiconductor body and a radiation entrance side. About the

Radiation inlet side can reach radiation to be detected in the semiconductor body, are absorbed there and subsequently generate a pair of charge carriers, in particular an electron-hole pair.

The semiconductor body has a detection area provided for the radiation reception, at least two electrical contact areas and at least one barrier area. Between the contact areas, a current path extends in Semiconductor body. During operation of the semiconductor component, charge carriers in the semiconductor body can flow from the one contact region to the other contact region via the current path. The barrier region and the detection region are arranged in the current path between the contact regions. The barrier region is preferably doped.

The barrier region is furthermore preferably suitable for forming a potential barrier and provided in particular. The potential barrier is preferably formed and, in particular, arranged between the detection region and the contact region which, viewed along the current path, is arranged on the side of the barrier region facing away from the detection region. During the operation of the semiconductor component, for example when the contact voltage is applied between the contact regions, it is possible, via the potential barrier, to hinder or even prevent a charge carrier flow from one contact region into the other contact region. The barrier region may be formed in such a way that a charge carrier flow from the one contact region into the other contact region before radiation absorption in the detection region is omitted and after radiation absorption charge carriers can flow from one into the other contact region.

In a preferred embodiment, the semiconductor component is designed and in particular operable such that in the semiconductor body, preferably in the detection region, a primary charge carrier, for example an electron or a hole, by impact ionization secondary charge carriers, for example an electron-hole pair or a plurality of electron -Hole pairs, can generate. The primary charge carrier, preferably an electron, can be generated by absorption of radiation to be detected in the detection area. The detection region can be designed such that the primary charge carrier can be generated by absorption of radiation in the detection region.

In a further preferred refinement, the semiconductor component is embodied and in particular operable such that a flow of charge carriers, for example of secondary charge carriers and / or charge carriers of a uniform charge carrier type (electrons or holes), which are generated in the semiconductor body and in particular in the detection region, from the Detection area through the barrier area and in that contact area, which is arranged along the current path on the side remote from the detection area of the barrier area, obstructed during operation of the device by means of the potential barrier or even prevented. Preferably, the charge carrier flow from one to the other contact area temporarily, more preferably only temporarily prevented or hindered.

In a further preferred refinement, the semiconductor component is embodied and in particular operable such that charge carriers, for example secondary charge carriers, of a charge carrier type generated in the semiconductor body and in particular in the detection region can drift to the barrier region and collect in the barrier region. By accumulating in the barrier region carriers, the height of the potential barrier can be reduced.

The charge carrier of the charge carrier type can be electrostatically attracted in the barrier region of ionized Dotierstoffatomrümpfen. The in the barrier area Accumulated charge carriers can recombine with the ionized Dotierstoffatomrümpfen. Electrons as charge carriers of this charge carrier type are suitably attracted to positively charged donor atomic bodies. Holes, as charge carriers of this charge carrier type, are suitably attracted to negatively charged acceptor bodies. The charge carriers collecting in the barrier region are preferably

Secondary carriers. Due to the higher effective mass, holes are particularly suitable for accumulation in the barrier area. In contrast, electrons are particularly suitable for the generation of secondary charge carriers by impact ionization, in particular due to the lower effective mass compared to holes.

In a further preferred refinement, the semiconductor component is designed or, in particular, operated such that, after the potential barrier has been reduced, charge carriers can flow from one contact region through the barrier region and the detection region into the other contact region. The charge carriers which flow from one to the other contact region are preferably charge carriers of the other charge carrier type - for example charge carriers of the type which do not collect in the barrier region or are impeded by the potential barrier. Preferably, the charge carriers of the other charge carrier type are electrons.

This has the advantage that a signal of the detector is not carried solely by the impact ionization as in an avalanche photodiode, but rather by a charge carrier flow from one contact region to the other contact region, which after sufficiently reducing the Potential barrier uses. The semiconductor component can be designed as a unipolar component, that is to say as a component in which only charge carriers of a charge carrier type, preferably electrons, contribute significantly to the signal.

In a further preferred embodiment, the semiconductor component has a control electrode. This is preferably suitable for the application of an electrical control field to the barrier region and is particularly preferably provided. The control field can be generated by means of a control voltage applied to the control electrode or a control potential applied to the control electrode. The control electrode may extend over the barrier area. The height of the potential barrier can be controlled via the control electrode and in particular the control voltage applied thereto or the control potential applied there. Expediently, a dielectric is arranged between the control electrode and the semiconductor body. The dielectric, for example a dielectric layer, preferably isolates the control electrode, in particular its entire surface, from the semiconductor body. The dielectric is expediently designed such that electrical breakdown to the control electrode during operation of the semiconductor component is avoided. The control electrode preferably extends over the detection area. By applying a suitable control voltage or a suitable control potential to the control electrode, a conductive channel for the carrier passage through the detection area can be formed in the detection area. The channel may, for example, be an n-channel be. The charge carrier passage through the detection area after the degradation of the Potentialbarrάere is facilitated.

If a photon is absorbed in the detection region during operation of the semiconductor component, further charge carriers can be generated by impact ionization in the detection region by means of the charge carriers generated by absorption. By charge carriers drifting to the barrier region, the barrier height can be reduced and a signal current can flow. The semiconductor component is particularly suitable and preferably designed for the detection of single photons or radiation pulses, in particular ultrashort pulses, for example in the nanosecond, picosecond or femtosecond range. Furthermore, the semiconductor device is suitable as a photon counter.

In a further preferred refinement, a blocking region in the semiconductor body is provided along the current path on the side of the barrier region which faces away from the detection region. The blocking region is preferably embodied such that, during operation of the component, tunneling of charge carriers from the barrier region in the contact region arranged on the side of the barrier region remote from the detection region along the current path can be avoided or reduced.

In a further preferred embodiment, the control electrode extends over one or a plurality of the following areas: detection area, blocking area.

In a further preferred embodiment, one or a plurality of the following ranges is embodied intrinsically: Detection area, restricted area.

In a further preferred embodiment, the contact regions are doped. The contact areas can be doped for the same line type or for different line types.

In a further preferred embodiment, the barrier region is doped for the same conductivity type as the contact regions.

In a further preferred embodiment, the barrier region is doped for a different conductivity type than the contact regions.

In a further preferred refinement, the detection area is preceded by one of the contact areas on the radiation entry side. In this contact region, a window for the radiation entry into the detection region can be formed.

In a further preferred refinement, an antireflection layer is arranged upstream of the detection area on the radiation entry side. The antireflection layer can be arranged in the window.

In a further preferred embodiment, the barrier area is designed highly doped. The barrier region may have a dopant concentration of 1 * 10 ¹⁹ l / cm ³ or more, 1 * 10 ²⁰ l / cm ³ or more, or 1 * 10 ²¹ l / cm ³ or more. In a further preferred embodiment, the barrier region is doped such that a sharp increase in the dopant concentration is formed in relation to regions of the semiconductor body which adjoin the barrier region along the current path. The

Dopant concentration along the current path in the transition from outside the barrier area to the barrier area or within the barrier area may be fivefold or more, preferably seven times or more, more preferably nine times or more, along the pathway over a distance of 10 nm or less. increase.

In a further preferred embodiment, the barrier region is doped in such a way that the semiconductor component has a triangular-shaped potential barrier in the energy band diagram between the contact regions along the current path.

In a further preferred refinement, the barrier region, the detection region and preferably the blocking region are matched to one another such that the semiconductor component has a triangular-shaped potential barrier in the energy band diagram between the contact regions along the current path.

In a further preferred embodiment, the barrier region along the current path has an extension of 20 nm or less, preferably 15 nm or less, particularly preferably 12 nm or less.

In a further preferred embodiment, the barrier region along the current path has an extent of 3 nm or more, preferably 5 nm or more, more preferably 10 nm or more.

In a further preferred embodiment, the detection region along the current path has an extension of 100 nm or more, preferably 300 nm or more, more preferably 500 nm or more.

In a further preferred embodiment, the detection region along the current path has an extent of between 100 nm and 1000 nm inclusive, preferably between 200 nm and 900 nm inclusive, more preferably between 300 nm and 800 nm inclusive.

In a further preferred refinement, the detection area along the current path has an extent which is greater than the extent of the blocking area along the current path.

In a further preferred embodiment, the semiconductor component is suitable for the detection of a single photon or a radiation pulse and in particular formed.

In a further preferred embodiment, the semiconductor component is suitable as a photon counter and in particular formed.

In a further preferred refinement, the semiconductor body is based on silicon.

In a further preferred embodiment, the semiconductor component is designed as a unipolar component. In a further preferred embodiment, the semiconductor body has one or a plurality of epitaxial layers.

In a further preferred embodiment, the semiconductor component is designed as a vertical component.

In a further preferred embodiment, the semiconductor body has a semiconductor layer stack, the semiconductor layer stack each having a separate layer for one, a plurality or all of the following areas: the one contact area, the other contact area, the barrier area, the detection area, the blocking area.

In a further preferred embodiment, the semiconductor component is designed as a lateral component.

In a further preferred embodiment, the contact regions, the barrier region and the detection region are arranged laterally next to one another, preferably in a common semiconductor layer.

In a further preferred refinement, the semiconductor component has a substrate on which the semiconductor body is arranged. The detection region may be electrically isolated from the substrate.

In a further preferred embodiment, the semiconductor component has a modified MOSFET structure, wherein one contact region for the source, the other contact region for the drain and the control electrode as Gate electrode is provided and wherein the detection area between the barrier region and the drain is arranged.

In a further preferred refinement, the detection region, which is a contact region, the other contact region, the blocking region, the control electrode and / or the dielectric is part of a transistor.

In a further preferred embodiment, the semiconductor device is different from a triangular-shaped barrier diode (triangular barrier diode).

According to one embodiment, a semiconductor device comprises a plurality of radiation receiving ends

Semiconductor devices of the type described above. The semiconductor device may be designed monolithically integrated. For example, the semiconductor device may comprise ten or more, preferably twenty or more, semiconductor devices. By a plurality of semiconductor devices, the available detection area is increased. In particular, the semiconductor device may have a substrate which is common to all semiconductor components of the semiconductor device, in particular a semiconductor substrate. This substrate may form one of the contact areas.

According to one embodiment, a radiation detector comprises a semiconductor component or a semiconductor device of the type described above. The radiation detector is preferably suitable for the detection of radiation having wavelengths outside the spectral sensitivity range of the detection region and is particularly preferably formed. In this case, the radiation detector preferably has a conversion element, which incident radiation, not in the detection area absorbed and therefore would not produce an electron-hole pair, converted into radiation that can be absorbed in the detection area. As a result, the radiation detector can be adapted to specific wavelength ranges of the radiation to be detected without the detection range having to be changed. This has advantages in the production of the semiconductor components for a radiation detector, since they can be prefabricated similarly and can be adapted with different conversion elements to different wavelengths to be detected. By way of example, the radiation detector can be designed to detect x-ray radiation. For this purpose, a scintillator can be provided as a conversion element.

A semiconductor device, a semiconductor device or a radiation detector as described above is also suitable for the analysis of the composition of a sample material, for example via detection of radiation generated by the sample material, in particular γ-radiation or X-radiation.

In one embodiment of a method for operating a radiation-receiving semiconductor component, a semiconductor device or a radiation detector of the type described above, first of all a contact voltage is applied between the two contact regions. As a result, an electric field extending through the detection region can form in the semiconductor component and in particular in the semiconductor body. The contact voltage and the semiconductor body, in particular the contact voltage and the detection range, are matched to one another in such a way that in the detection range by absorption generated charge carriers of a charge carrier type in the semiconductor body and in particular in the detection region can generate further charge carriers by impact ionization. The potential barrier formed by the barrier region and the contact voltage are further tuned to one another in such a way that a signal current flow from one contact region to the other contact region is prevented.

Signal current flow is understood to mean a current signal which is significantly different from background noise, which is caused, for example, by a dark current.

Subsequently, radiation, in particular a single photon or a radiation pulse, is absorbed in the detection area. In this case, at least one primary charge carrier of a charge carrier type, for example an electron or a hole, is generated in the detection region. By impact ionization by the primary charge carrier are then

Secondary charge carriers, in particular electron-hole pairs, generated in the detection area. For impact ionization, the primary charge carrier is expediently accelerated in the electric field in the detection region in such a way that impact ionization occurs. Charge carrier-type secondary carriers, for example, holes, drift to and collect at the barrier region, thereby reducing the potential barrier. If necessary, additional secondary charge carriers can also be generated by secondary charge carriers via impact ionization. Overall, so can accumulate a variety of secondary carriers in the barrier area. The potential barrier can be reduced in particular by the secondary charge carriers of a charge carrier type such that a signal current flows from one contact region to the other Contact area flows. The signal flow expediently flows through the barrier area and the detection area.

The flowing signal current can subsequently be detected. If a current flows, this means that radiation has hit the detection area.

The charge carriers accumulated in the barrier region preferably do not or not significantly contribute to the signal current.

The height of the potential barrier is expediently selected such that it can be reduced to such an extent by charge carrier accumulation of secondary charge carriers generated by impact ionization that a signal current can flow through the contact regions.

Before the radiation absorption, a predetermined control voltage or a predetermined control potential, which is suitable for forming a potential barrier which can be decomposed up to the signal current flow by means of the secondary charge carriers, can be determined and applied to the barrier region. This is expediently carried out via the control electrode. The height of the potential barrier can be varied via the control electrode. The control electrode can thus to

Operating point setting of the semiconductor device can be used.

After the signal current has flowed and in particular has been detected, by applying a suitably polarized voltage, for example a suitably polarized control voltage or a suitable control potential, to the Barrier area the secondary cargo carrier drifted into the barrier area removed from the barrier area, in particular deducted ("sucked"), be. This peeling causes the barrier to rebuild and the signal current flow to be inhibited.

After removal of the secondary charge carriers from the barrier region, the radiation detector is again in the initial state, so that a further detection process can be started. This can begin with the absorption of radiation in the detection area, as described above.

The process of sucking the secondary charge carriers out of the barrier region can advantageously be carried out more quickly than the removal of the very high blocking voltage across the avalanche photodiode by the quenching described above.

Furthermore, compared to an avalanche photodiode, the semiconductor device can be operated with an advantageously low voltage. This results from the fact that charge carriers generated by impact ionization essentially serve only for the degradation of the barrier and do not have to contribute significantly to the signal as in the case of the avalanche photodiode.

The contact voltage may be 75 V or less, preferably 60 V or less, more preferably 50 V or less. The contact voltage may be 20 V or more, preferably 30 V or more, more preferably 40 V or more. Due to the advantageously low contact voltage, the semiconductor devices in a semiconductor device, the individual semiconductor devices are packed tightly, without the risk of electrical (voltage) breakdown between two adjacent Increase semiconductor devices. The quantum efficiency per area can be increased with advantage.

The control voltage may be half the contact voltage or less.

The signal current can be 0.1 mA or more.

Further advantages, features and advantageous embodiments will become apparent from the following description of the embodiments in conjunction with the figures.

FIG. 1 shows an embodiment of a

Radiation-receiving semiconductor device based on a schematic sectional view.

FIG. 2 shows, with reference to FIGS. 2A, 2B and 2C, schematic energy band diagrams for different operating states of the semiconductor component according to FIG. 1.

Figure 3 shows a plan view of an embodiment of a semiconductor device having a plurality of semiconductor devices.

FIG. 4 shows a schematic sectional view of a

Embodiment of a radiation detector.

FIG. 5 shows a further exemplary embodiment of a

Radiation-receiving semiconductor device based on a schematic sectional view. The same, similar and equally acting elements are provided in the figures with the same reference numerals. The individual elements shown in the figures are not necessarily drawn to scale. Rather, individual elements in the figures may be exaggerated in size for clarity.

FIG. 1 shows an embodiment of a

Radiation-receiving semiconductor device 1 based on a schematic sectional view.

The radiation-receiving semiconductor component 1 has a semiconductor body 2. The semiconductor component further has a radiation entrance side 3.

The semiconductor body 2 has two electrical contact areas 4, 5. Between the contact regions 4 and 5, in particular from the contact region 5 up to and into the contact region 6, an electrical current path 6 extends in the semiconductor body 2. In the current path 6 between the contact regions 4 and 5 and in particular also spatially between the contact regions is a detection region 7 of the semiconductor device 1 in the semiconductor body 2 is arranged. The semiconductor body 2 also has a barrier region 8. The barrier region 8 is arranged in the current path 6 between the detection region 7 and the contact region 5 and in particular also spatially between the detection region 7 and the contact region 5. The barrier area 8 is preferably arranged on the side of the detection area 7 facing away from the radiation entrance side 3.

Furthermore, the semiconductor body 2 has a blocking region 9. The blocking region 9 is in the current path 6 between the Barrier area 8 and the contact area 5 and in particular also arranged spatially between the barrier area 8 and the contact area 5.

The semiconductor body 2 may comprise a layer stack, wherein in each case layers for the contact area 5, the blocking area 9, the barrier area 8, the detection area 7 and / or the contact area 4 are provided. Thus, a contact layer 4, a detection layer 7, a barrier layer 8, a barrier layer 9 and / or a contact layer 5 can be provided. The respective layers may be embodied as separate layers. In particular, the respective layers may be grown epitaxially, for example by MBE (MBE: molecular beam epitaxy) or by means of a CVD epitaxy process (chemical vapor epitaxy). The contact region 5 can be formed by the growth substrate on which the layers are epitaxially deposited. Thus, it is not necessary to provide a separately grown contact layer 5, but instead the growth substrate can be used, as shown in FIG.

The component shown in Figure 1 is designed as a vertical component. In a vertical component layers for the individual areas can be stacked one above the other. A current flow can take place in vertical components perpendicular or substantially perpendicular to a lateral main extension direction of the layer stack of the semiconductor body 2, which can be aligned along a main surface of the substrate.

After the epitaxial growth of the individual layers for the semiconductor body, a mesa can emerge from the epitaxial layers be formed. For example, reactive ion etching using a suitable mask, for example a (metal or nitride) hard mask, is suitable for this purpose. The mesa can extend from the radiation entrance side 3 of the semiconductor component 1, which is preferably the side of the semiconductor layer stack facing away from the substrate, as far as or even into the contact region 5, that is to say possibly into the substrate.

The contact region 5, the blocking region 9, the barrier region 8, the detection region 7 and / or the contact region 4 may contain silicon or consist of silicon, wherein individual regions may optionally be doped.

The radiation-receiving semiconductor component 1 has two electrical connections 10, 11. The connection 10 is expediently arranged on the contact region 4 and the connection 11 on the contact region 5. The respective terminal 10, 11 is suitably connected in an electrically conductive manner to the contact region 4 or 5 assigned to it. Via the terminals 10 and 11, a signal current which flows through the contact regions 4, 5 and the semiconductor body 2, can be detected in a simplified manner. The connections can be designed, for example, in each case as a connection metallization or connection alloy. A metal or metal-like material is particularly suitable for port 10 or 11.

Furthermore, the semiconductor component 1 has a control electrode 12. The control electrode 12 may extend along a side surface of the semiconductor body 2 which delimits it laterally and preferably from the radiation entrance side 3 in the direction of the contact region 5 extends, extend. The control electrode 12 may extend in particular over the detection area 7, the barrier area 8 and / or the blocking area 9. The Steυerelektrode 12 may contain silicon, for example highly doped poly-silicon, or other electrically conductive material, for example a metal or a metal alloy. The control electrode 12 is preferably electrically conductively connected to a control terminal 13, for example a metallization or metal alloy. The control electrode can circulate the detection area 7, the barrier area 8 and / or the blocking area 9. A control voltage or an electrical control field can be applied to the semiconductor body 2 and in particular to the detection area 7, the barrier area 8 and / or the blocking area 9 via the control electrode 12 and in particular the control terminal 13.

Between the control electrode 12 and the semiconductor body 2, a dielectric layer 14 is arranged, via the dielectric layer 14, the control electrode 12 is electrically isolated from the semiconductor body 2. The dielectric layer can be realized for example by thermal growth or by deposition on the semiconductor body. For example, a silicon oxide, a silicon nitride or another electrically insulating material is suitable for the dielectric layer. A thickness of the dielectric layer 14 is expediently dimensioned such that upon application of a predetermined contact voltage between the contact regions 4 and 5 and the simultaneous application of a control voltage suitable for the operation of the component or a suitable control potential by means of the control electrode, an electrical breakdown of one of the contact regions 4, 5 or one of Connections 10, 11 is avoided to the control electrode 12. For example, the dielectric layer has a thickness of 10 nm or more, preferably 20 nm or more, more preferably 50 nm or more, for example, 70 nm or more, or 100 nm or more.

The dielectric layer 14 can cover the detection area 7, the barrier area 8 and / or the blocking area 9 laterally circumferentially on the outside.

The detection area 7 is provided for the absorption of radiation to be detected, which incident on the radiation entrance side into the semiconductor body 2. In order to avoid unwanted radiation absorption in the detection region 7 upstream of the radiation inlet elements, a window 15 extending to the detection region 7 may be formed in the semiconductor body 2. The radiation inlet side arranged contact region 4 may be recessed for the window 15. In particular, the terminal 10 can be recessed.

Radiation can thus enter the detection area unhindered by the material of the semiconductor body 2 or of the connection 10, in which a significant proportion of radiation can be absorbed, the absorbed radiation correspondingly no longer reaching the detection area 7. The risk of absorption losses is thus reduced. Particularly high absorption losses often result in doped semiconductor material or in metals.

In order to facilitate the entry of the crystals into the detection area 7, the detection area 7 can be used On the radiation entrance side, an antireflection coating 16, for example a suitable silicon oxide or silicon nitride coating, may be arranged. Reflection losses at a radiation entrance surface 17 in the detection area can thus be at least reduced. The anti-reflection coating 16 is preferably disposed within the window 15.

The radiation-receiving semiconductor component 1 is preferably suitable for detecting single-photon or radiation pulses, in particular ultrashort radiation pulses, for example with a pulse duration of 500 ns or less, of 900 ps or less or of 100 fs or less, and in particular. At low numbers of photons, an absorption outside the detection range or a reflection at the detection range, which in each case does not lead to a radiation entry into the detection range, of course, particularly significant.

The detection area 7 is designed such that secondary charge carriers can be generated via impact ionization of primary charge carriers. A primary charge carrier may be, for example, an electron or hole produced by absorption of radiation in the detection region. The detection region preferably has an extension, for example a thickness, along the current path 6, which is large enough to be able to achieve one or a plurality of impact ionizations with the primary charge carrier. The path length available for accelerating the charge carriers for the generation of secondary charge carriers by impact ionization is then advantageously sufficiently large. However, it may also be advantageous not to detect the detection area with too great an extent, for Example, the thickness, form, to avoid recombination of impact ionization generated secondary carriers in the detection area.

An extension of the detection region 7 along the current path, for example the thickness, of between 100 nm and 1000 nm inclusive, preferably between 200 nm and 900 nm inclusive, more preferably between 300 nm and 800 nm inclusive, for example between 350 nm and 500 nm, such as 400 nm, has been found to be particularly suitable. Such extensions both provide a sufficiently long distance to generate

Secondary carriers available and at the same time increase the risk of recombination unnecessary.

The barrier region 8 is expediently designed such that, during operation of the component, a charge carrier flow of charge carriers generated in the detection region 7 by absorption and / or impact ionization through the barrier region and to the contact region 5, preferably only temporarily, can be prevented. In particular, a potential barrier can be formed between the detection region 7 and the contact region 5 by means of the barrier region 8. The height of the potential barrier can be set via the control voltage or the applied control potential applied to the control electrode 12.

Charge carrier tunneling from the barrier region 8 into the contact region 5 can be prevented via the blocking region 9. This has the advantage that a tunnel current does not contribute to the dark current of the component, or only with great difficulty can. The stopband may have an extension along the current path that is less than that of the detection region. The extension of the stop band 9, for example, the thickness, may be 20 nm or more and / or 50 nm or less.

The detection area 7 may have an extent along the current path 6 which is eight times or more the extent of the blocking area along the current path 6.

The barrier region 8 may have an extension, for example a thickness, of 20 nm or less, preferably of 15 nm or less, particularly preferably of 12 nm or less, along the current path. The extent is preferably 3 nm or more, more preferably 5 nm or more, for example, 10 nm or more. An extension of the barrier area of between each including 10 nm and 20 nm has been found to be particularly suitable for the barrier area.

The contact regions 4, 5 and the barrier region 8 are expediently doped, in particular n-type or p-type doped. The contact regions and the barrier region can be doped for the same conductivity type (p-type or n-type). The contact areas may alternatively be doped for different types of lines. The barrier region 8 may be doped for a different conductivity type than one of the contact regions 4, 5 or both contact regions.

The detection area 7 and / or the blocking area 9 is preferably intrinsic, that is to say undoped. The structure of the radiation-receiving semiconductor component 1 can thus correspond to that of a modified MOSFET, the contact region 5 serving as the source, the contact region 4 as the drain, and the control electrode 12 as the gate electrode. Between the barrier area 8 and the drain, the detection area 7 is arranged. Between the source and the barrier region 8, the blocking region 9 is arranged.

Due to a control voltage applied to the control electrode 12 or an applied control potential, an electrically conductive channel, for example an n-channel or a p-channel, along the current path 6 in regions of the semiconductor body 7, over which the control electrode 12 extends to the Example in the detection area 7 and / or the blocking area 9, form.

The semiconductor component 1 is furthermore preferably designed in such a way that, during operation in the energy band diagram, a potential barrier is formed along the current path 6 between the contact regions 4 and 5. The potential barrier preferably has a triangular shape. A triangular shaping of the potential barrier has proven to be particularly suitable for the generation of charge carriers by impact ionization in the detection region 7. The potential barrier is expediently formed by means of the barrier region 8.

FIG. 2 shows schematic energy band diagrams for different operating states of the semiconductor component 1 according to FIG. FIG. 2A shows the energy band profile along the current path 6 from the contact region. 4 via the detection area 7, the barrier area 8, the blocking area 9 to the contact area 5. Between the contact areas 4, 5 no potential difference (contact voltage) is applied. Furthermore, no control potential difference (control voltage) is applied by means of the control electrode 12 to the semiconductor body. Shown are the valence band V, the conduction band L and the Fermi level F.

The contact regions 4, 5 are doped n-type, for example. The detection area 7 and the stopper area 9 are implemented intrinsically (i), for example. The barrier region 8 is p-doped, for example. The barrier region 8 is preferably highly doped (p ⁺⁺ ), for example with a dopant concentration of 1 × 10 ¹⁹ l / cm ³ or more, preferably of 1 × 10 ²⁰ l / cm ³ or more, particularly preferably of 5 × 10 ²⁰ l / cm ³ or more formed. The contact regions 4, 5 may be formed with a dopant concentration of 1 × 10 ²⁰ l / cm ³ or less. The individual areas can be based on silicon. For example, phosphorus is suitable as a dopant for n-type doping, and boron is suitable as a dopant for p-type doping.

Furthermore, the doping profile course along the current path during the transition from the detection area 7 to the barrier area 8 preferably has a steep rise in the dopant concentration. In the transition from the barrier region 8 to the stop region 9, there may be a steep drop in the dopant concentration.

The dopant profile of the barrier area with respect to the adjacent areas - for example, the (intrinsic) Detection area 8 and in particular the (intrinsic) stopband 9 - may be approximated to a Dirac δ function. Therefore, such a highly doped and preferably thin barrier layer layer can also be referred to as δ-layer.

The dopant concentration of the dopant of the barrier region 8 may be fivefold or greater, preferably sevenfold or greater, more preferably ninefold, in the transition from outside the barrier region to the barrier region or within the barrier region over a distance of 10 nm or less or more, increase. A barrier region doped with such a sharp transition in the dopant profile is particularly advantageous for the formation of an electric field by the potential gradient in the detection region, the electric field being suitable for generating secondary charge carriers by impact ionization during operation of the semiconductor component.

Between the contact regions 4, 5, a triangular shaped potential barrier P is formed. Expediently, the detection area 7 and the barrier area 8 and, if appropriate, the blocking area 9 are matched to one another such that the triangular-shaped potential barrier results in the energy band diagram. The barrier region 8 is arranged in the region of the apex of the triangle, wherein the triangular tip can be made flattened as shown. The length of the flattened piece may be the thickness of the barrier area or less than the thickness of the barrier area. FIG. 2B shows the energy band diagram from FIG. 2A with a contact voltage V _K applied to the contact regions 4, 5. The voltage is applied so that the electric potential at the contact region 4 is greater than the electric potential at the contact region 5 (positive contact voltage). This causes the energy bands L, V to move downwardly from the contact area 4. The shift may be proportional to V _κ .

The contact voltage may be 75 V or less, preferably 60 V or less, more preferably 50 V or less. The contact voltage may in particular be between in each case including 20 V and 75 V, preferably between in each case including 30 V and 60 V, particularly preferably between in each case including 40 V and 50 V. In this case, the majority of the contact voltage can drop over the detection area 7. In particular, a steep potential gradient forms from the barrier region 8 via the detection region 7 to the contact region 4. The potential gradient can be 10 ⁴ V / cm greater, preferably 5 × 10 ⁴ V / cm or greater. Such a large potential gradient is particularly suitable for impact ionization.

Between the contact regions 4, 5, the potential barrier P is formed. Thus, no signal current flows from the contact region 5 to the contact region 4

Semiconductor component 1 is thus biased such that no signal current flows from the contact region 5 to the contact region 4.

If a photon is absorbed in the detection area, a primary electron-hole pair is formed (E _p , H _p ). The electron E _p is along the potential gradient, which is caused in particular by the potential barrier and the contact voltage, accelerated in the direction of the contact region 4 and can generate secondary electron-hole pairs (E ₃ , Hg) by impact ionization. This is indicated by, the arrows in the conduction band L and the double arrows between conduction band L and valence band V. The electrons - primary and secondary electrons - flow away to contact area 4 (drain).

The holes generated by impact ionization in the detection region 7 - primary and secondary holes - flow to the barrier region 8. The holes are accelerated by the potential gradient, in particular in the direction of the barrier region 8. In the barrier region 8, numerous negatively charged acceptor atomic bodies are present due to the p-doping. By entering into the barrier region 8, positively charged and there accumulating holes at least a portion of the negative charges of the acceptor atomic bodies is compensated, so that the height of the potential barrier P is reduced. The holes can in particular recombine with the dopant fumes in the barrier region.

Figure 2C shows the situation after reduction of the potential barrier P.

The height of the potential barrier can be reduced so much by the accumulation of secondary charge carriers in the barrier region 8 alone that a signal current I, which in particular from the

Majority carriers of the contact areas - in the present case the electrons - is carried, flows from the contact region 5 (source) to the contact region 4 (drain). The signal current can have a thickness of 0.1 mA or more, preferably 1 mA or more. Conveniently, the semiconductor device 1 is dimensioned such that it can pass such currents destructive.

The holes accumulated in the barrier region 8 preferably remain in the barrier region after the potential barrier has been reduced to the signal current flow. The holes can be kept in the barrier area in particular by the previously ionized dopant atoms and / or already be recombined with them. Furthermore, holes have a higher effective mass than the electrons, so that even a comparatively small residual potential barrier is sufficient to hold the holes in the barrier region, while the electrons can overcome such a residual potential barrier as opposed to the holes.

Holes preferably do not contribute to signal current I, or at least not significantly. The component is thus a unipolar component whose current is carried only by charge carriers of a charge carrier type (in the present example: electrons).

The charge carriers E ₃ , H _s generated by impact ionization do not contribute significantly to the signal, but rather serve only for barrier degradation and enable a signal current flow through the degradation of the barrier.

The height of the potential barrier is preferably dimensioned such that at a predetermined contact voltage before the radiation incidence no signal current flows between the contact regions 4, 5. Furthermore, the height of the potential barrier to the detection area 7 and / or the Contact voltage V ^ suitably adjusted so that the potential barrier can be reduced as far as generated by impact ionization charge carriers that - caused already advantageously by the incidence of a single photon - a signal current can flow between the contact areas.

In this case, the barrier height can expediently be set by the control electrode 12 and in particular via an electrical control field or an applied control voltage or control potential V ₃ applied to the barrier area by means of this control electrode. By means of the control electrode 12, the operating point of the semiconductor device can be adjusted. In particular, it is therefore not necessary to manufacture the component already with a predetermined barrier height, but the height of the barrier can be suitably adjusted via the control electrode, for example by means of a previously determined predetermined control voltage or a control potential.

If, for example, a positive control voltage V _{3 is applied} to the component, then the band profile shown in dashed lines in FIG. 2B can result between the contact regions 4, 5. The barrier can therefore be lowered, for example.

In particular, a single photon can be sufficient to trigger a significant measurable current signal of the semiconductor component 1. If the signal is detected, a single photon or even a radiation pulse can be detected efficiently. If a suitably polarized voltage is applied to the control electrode after the signal current flow, for example a negative voltage for holes, then the charge carriers accumulated in the barrier region can be removed from the barrier region ("sucked off"). As a result, the barrier increases again. A signal current flow can then be prevented again. The detector is then in the initial state and ready for a new radiation detection.

The radiation detector can, via the control electrode, in particular from the signal current flow, in a time interval of 1 ms or less, preferably 1 μs or less, more preferably 50 ns or less, for example 10 ns or less, 1 ns or less, from 100 ps or less, or from 50 ps or less, to the initial state. The time interval can be between 1 ns and 10 ns in each case.

Accordingly, sequential detection operations may in particular be performed at a frequency of 1 kHz or more, preferably 50 kHz or more, more preferably 300 kHz or more, for example 1 MHz or more, 20 MHz or more, 100 MHz or more 1 GHz or more, 10 GHz or more, or 20 GHz or more.

A comparatively time-consuming resetting of the semiconductor device 1 in the initial state via quenching as in the avalanche photodiode can be avoided.

The profile of the doping profile from the contact region 4 along the current path 6 via the detection region 7, the barrier region 8 and in particular the blocking region 9 to the contact region 5 is merely exemplary in FIG nipin indicated. Optionally working components may also be formed with the following doping profiles: pinip, ninip, pipin, pipip or ninin.

If the barrier region is formed by means of an n-type doped barrier region, the role of electrons and holes would be correspondingly reversed. Also the polarity of the applied voltages / potentials might be suitable to reverse.

Since the charge carriers generated by impact ionization do not contribute significantly to the signal, the semiconductor device can be operated at significantly lower voltages than an avalanche photodiode. Rather, the signal current can be formed exclusively or predominantly by the current flowing between contact regions, the charge carriers generated by impact ionization essentially serving only for breaking down the potential barrier. In particular, the full amplification factor of the modified transistor underlying the semiconductor component can lead to the signal. The amplification factor may be 10 ⁴ or more, preferably 10 ⁵ or more.

Since impact ionization is not the mechanism governing the signal current strength, the semiconductor device can be operated with analog dimensioning to a given avalanche photodiode in comparison with the avalanche photodiode with much lower contact voltages (operating voltages).

This has a particular advantage in the formation of a semiconductor device having a plurality of such Semiconductor devices. Since the operating voltage (contact voltage) is comparatively low, the semiconductor devices can be packed more densely against avalanche photodiodes and / or electrical insulation between adjacent semiconductor devices can be made smaller, for example thinner, without the risk of crosstalk or electrical breakdown between is increased adjacent semiconductor devices.

With an increase in the packing density of

Semiconductor components, the area available for the radiation detection surface of the semiconductor device and in particular the quantum efficiency per unit area increased.

FIG. 3 schematically shows a plan view of such a semiconductor arrangement 100 with a plurality of semiconductor components 1, which are expediently designed and in particular operable as described above. The semiconductor device may be monolithically integrated. A single contact region 5 may be common to all semiconductor devices 1 of the semiconductor device 100.

The semiconductor devices 1 may be made, for example, from a common epitaxial layer sequence grown on a substrate. In this case, the substrate can form the contact region 5 common to all semiconductor components 1 of the semiconductor arrangement 100.

FIG. 4 shows a schematic sectional view of an exemplary embodiment of a radiation detector 200. In this case, the radiation detector 200 has a semiconductor device 100 or a semiconductor device 1 as above described on. Radiation inlet side of the semiconductor device or the semiconductor device, a conversion element 18 is arranged upstream.

In the conversion element 18, radiation 19 whose wavelength is outside the spectral sensitivity range of the detection region and therefore can not generate a primary charge carrier can be converted into radiation 20 whose wavelength lies within the spectral sensitivity range of the detection region and which can therefore generate a primary charge carrier.

The radiation 19 may be, for example, X-radiation or γ radiation. As a conversion element, for example, a scintillator is suitable. This can generate radiation 20 within the sensitivity range of the detection region of the semiconductor component 1 or the semiconductor arrangement 100, which is preferably based on silicon.

In this case, the number of photons of the radiation 20 generated in the conversion element 18 is preferably proportional to the energy of the radiation 19 incident on the conversion element or of the energy of the incident radiation quantum. The signal obtained in the semiconductor device 100 or the semiconductor device 1 is preferably proportional to the number of absorbed photons of the radiation 20. In this way, an energy-resolved measurement of the incident radiation 19 can be achieved.

FIG. 5 shows a further exemplary embodiment of a radiation-receiving semiconductor component 1 with reference to FIG schematic sectional view. In contrast to the semiconductor component described in connection with FIG. 1, which is designed as a vertical component, the component according to FIG. 5 is designed as a lateral component. However, the basic structure corresponds to the semiconductor device described above. In contrast, the individual regions, that is to say the contact regions 4, 5, the detection region 7, the barrier region 8 and / or the blocking region 9 are arranged laterally next to one another in the semiconductor body 2 and are preferably formed in a semiconductor layer 21. The dielectric layer 14 may be recessed for the window 15. The anti-reflection coating 16 may be disposed in the window 15 of the dielectric layer. The basic mode of operation of the component corresponds to that described above in connection with the other exemplary embodiments.

The semiconductor layer 21 may be disposed on a substrate 22. An insulating layer 23 may be arranged between the substrate 22 and the semiconductor body 2, which in the present case may be formed by a single semiconductor layer 21. A prefabricated structure with the substrate 22 of the insulating layer 23 and the semiconductor layer 21 can be acquired, for example, as a silicon-on-insulator substrate from SOITEC.

The current path 6 extends laterally along a main lateral extension direction or plane of the semiconductor layer 21 or of the substrate 22. The semiconductor layer 21 can be grown monocrystalline and in particular epitaxially.

The individual doped regions of the semiconductor layer can be formed by implantation of dopants. A lateral component is less expensive than a vertical component in manufacturing. Thus, a lateral component is particularly suitable for mass production.

The insulating layer 23 can prevent the outflow of charge carriers from the semiconductor body 2 into the substrate.

This patent application claims the priority of German patent application DE 10 2008 011 280.1 dated 27 February 2008, the entire disclosure content of which is hereby explicitly incorporated by reference into the present patent application.

The invention is not limited by the description with reference to the embodiments. Rather, the invention encompasses any novel feature as well as any combination of features, including in particular any combination of features in the claims, even if this feature or combination itself is not explicitly stated in the claims or exemplary embodiments.

Claims

claims

A radiation-receiving semiconductor device having a semiconductor body and a radiation entrance side, wherein

the semiconductor body has a detection area provided for the radiation reception, at least two electrical contact areas and at least one doped barrier area,

a current path extends between the contact regions in the semiconductor body,

the barrier region and the detection region are arranged in the current path between the contact regions,

the barrier region is suitable for forming a potential barrier which is arranged between the detection region and the contact region which, viewed along the current path, lies on the side of the barrier region which faces away from the detection region,

the component has a control electrode for applying an electric control field to the barrier region,

- Between the control electrode and the semiconductor body, a dielectric is arranged, and

- The height of the potential barrier is controllable via the control electrode.

2. The semiconductor device of claim 1, wherein the control electrode extends beyond the barrier region.

3. Semiconductor component according to claim 1 or 2, which is designed such that a primary charge carrier in the detection region can generate secondary charge carriers by impact ionization.

4. A semiconductor device according to at least one of claims 1 to 3, in which, viewed along the current path, a blocking region is provided in the semiconductor body on the side of the barrier region facing away from the detection region.

5. The semiconductor device according to claim 4, wherein the control electrode extends over one or a plurality of the following areas: detection area, blocking area.

6. A semiconductor device according to at least one of claims 1 to 5, wherein the detection region is arranged upstream of one of the contact areas of the radiation inlet side and in this contact area a window for the radiation entry is formed in the detection area.

7. The semiconductor device according to at least one of claims 1 to 6, wherein the detection region is disposed upstream of the radiation inlet side, an anti-reflection layer.

8. A semiconductor device according to claim 6 and 7 or a claim dependent thereon, wherein the anti-reflection layer is arranged in the window.

9. A semiconductor device according to any one of claims 1 to 8, wherein the detection region along the current path has an extension which is greater than the extension of the stopband along the current path.

10. A semiconductor device according to any one of claims 1 to 9, which is designed as a unipolar device.

11. A semiconductor device according to any one of claims 1 to 10, wherein the device has a modified MOSFET structure, wherein a contact region for the source, the other contact region for the drain and the control electrode is provided as a gate electrode and wherein the detection area between the barrier region and the drain is arranged.

12. Radiation detector with a semiconductor component according to at least one of the preceding claims for the detection of radiation outside the spectral

Sensitivity range of the detection area, wherein the radiation detector comprises a conversion element that converts incident radiation into radiation within the spectral sensitivity range of the detection area.

13. A method of operating a radiation-receiving semiconductor device or a radiation detector according to at least one of the preceding claims, comprising the steps of: a) applying a contact voltage between the two

Contact areas, wherein the contact voltage and the detection range are matched to one another such that in the detection range generated by absorption carriers of a

Charge carrier type in the detection region by impact ionization can produce further charge carriers, and wherein the potential barrier formed by the barrier region and the contact voltage are coordinated such that a signal flow is prevented from the one contact region to the other contact region; b) absorption of radiation, in particular of a single photon or of a radiation pulse, in the detection region while generating at least one primary charge carrier of a charge carrier type in the detection region by the absorbed radiation; c) generation of secondary charge carriers by impact ionization by the primary charge carrier in the detection area; d) Reduction of the potential barrier by

Charge carrier-type secondary carriers that drift and collect to the barrier region such that a signal current flows from one contact region to the other contact region.

14. A method according to claim 13, wherein the contact voltage is 50 V or less.