KR20160137858A - Semiconductor radiation detecting device - Google Patents

Abstract

One embodiment of the present invention provides a semiconductor radiation detecting device, comprising: a radiation-sensitized semiconductor where a charge is generated by incident of a radiation ray; a first electrode disposed in a first area of the semiconductor to apply a voltage to the semiconductor; a second electrode disposed in a second area of the semiconductor to collect the generated charged; and a plurality of nanostructures arranged on at least one surface of the first and second areas.

Description

Technical Field [0001] The present invention relates to a semiconductor radiation detecting device,

The present invention relates to a semiconductor radiation detection element, and more particularly, to a semiconductor radiation detection element with improved charge collection efficiency.

In general, a semiconductor radiation detecting element generates charges (electrons, holes) in a detecting element by ionizing action of incident radiation, collects it by an electric field applied between the electrodes, and detects incident radiation as a signal.

Such a semiconductor radiation detecting element is applied to various fields such as a medical imaging apparatus and a nondestructive inspection detector, and it is required to obtain a clear image of a certain level or higher with only a small amount of radiation. In other words, it is important to collect the generated charge with high efficiency in order to obtain high energy resolution for incident radiation.

The higher the mobility of the charge (electrons and holes) and the larger the electric field strength, the better the charge collection efficiency. However, even in the case where there is no incident radiation, there is a leakage current corresponding to the applied voltage, which may cause deterioration of energy resolution.

Monocrystalline and polycrystalline semiconductors used as semiconductor radiation detecting elements can be semiconductors having high resistivity (e.g., 10 ⁹ ? Cm or more) due to low charge concentration. However, due to the work function of the metal electrode, which is not suitable for such a high-resistance semiconductor, the Schottky barrier is formed at the interface between the electrode for charge collection and the semiconductor, so that it is difficult to make ohmic contact. So that the driving stability of the device for a long time is lowered. On the other hand, a noble metal such as Au or Pt with high purity (e.g., 99.99% or more) is required as an electrode material for ohmic contact, which causes an increase in cost.

Korean Patent Laid-Open Publication No. 2004-0091257 (published Oct. 28, 2004) Korean Patent Laid-Open Publication No. 2011-7022171 (published on November 23, 2011)

One of the problems to be solved by the present invention is to provide a semiconductor radiation detecting element with improved charge collection efficiency by changing electrical characteristics at the interface between the electrode and the semiconductor.

According to an embodiment of the present invention, there is provided a semiconductor device including: a radiation-sensitive semiconductor in which electric charges are generated by radiation incidence; a first electrode disposed in a first region of the semiconductor and applying a voltage to the semiconductor; And a plurality of nanostructures arranged on a surface of at least one of the first region and the second region.

According to an embodiment of the present invention, by introducing an array of nanostructures such as various types of particles at the interface between the electrode and the semiconductor at the interface, an inhomogeneous Schottky barrier is formed at the interface to locally lower the effective Schottky barrier height And as a result, it is possible to provide a semiconductor radiation detection element with improved charge collection efficiency.

When using high-resistance compound nanostructures, the interface recombination rate can be further reduced through local passivation and the charge collection efficiency can be increased.

In addition, by using a metal having a low electron affinity or a low first ionization energy as a nano structure, the polarization phenomenon can be mitigated, and high reliability can be ensured even when the semiconductor radiation detecting element is used for a long time.

The various and advantageous advantages and effects of the present invention are not limited to the above description, and can be more easily understood in the course of describing a specific embodiment of the present invention.

1A and 1B are a perspective view and a side sectional view, respectively, of a semiconductor radiation detecting element according to an embodiment of the present invention.
Figure 2 shows a band diagram of an electrode-semiconductor interface in which nanoparticle arrays are introduced.
3 is a schematic view showing a radiation measurement system having the semiconductor radiation detection element shown in FIG. 1A.
4 is a side view showing a semiconductor radiation detecting element according to another embodiment of the present invention.

Hereinafter, various embodiments of the present invention will be described in detail with reference to the accompanying drawings.

The embodiments may be modified in other forms or various embodiments may be combined with each other, and the scope of the present invention is not limited to the embodiments described below. Further, the embodiments are provided so that those skilled in the art can more fully understand the present invention. For example, the shapes and sizes of the elements in the drawings may be exaggerated for clarity of description, and the elements denoted by the same reference numerals in the drawings are the same elements. Also, in this specification, terms such as "upper", "upper surface", "lower", "lower surface", "side surface" and the like are based on the drawings and may actually vary depending on the direction in which the devices are arranged.

The term " one example " used in this specification does not mean the same embodiment, but is provided to emphasize and describe different unique features. However, the embodiments presented in the following description do not exclude that they are implemented in combination with the features of other embodiments. For example, although the matters described in the specific embodiments are not described in the other embodiments, they may be understood as descriptions related to other embodiments unless otherwise described or contradicted by those in other embodiments.

1A and 1B are a perspective view and a side sectional view, respectively, of a semiconductor radiation detecting element according to an embodiment of the present invention.

1A and 1B, a semiconductor radiation detecting element 10 according to the present embodiment includes a radiation sensitive semiconductor 11 and first and second radiation detecting elements 11 and 12 disposed on opposite sides of the radiation sensitive semiconductor 11, respectively. And a second electrode (12, 15).

The semiconductor radiation detecting element 10 may be an MSM (metal electrode-semiconductor-metal electrode) type Schottky barrier type device. In the present embodiment, the first and second electrodes 12 and 14 are illustrated as being arranged on opposite surfaces, respectively, but they may be arranged on the same surface in other elements such as MOSFETs. The present embodiment can be employed in a direct type structure in which radiation is directly incident on the detecting element 10 without passing through a scintillator or the like.

The radiation-sensitive semiconductor 11 may be a single crystal or a polycrystalline semiconductor in which charges are generated by the incidence of radiation. A semiconductor having a large resistivity can be preferably used for high resolution. The resistivity of the semiconductor 11 may be 10 ⁸ ? Cm or more, preferably 10 ⁹ ? Cm or more. Particularly, a compound semiconductor composed of an element having a high atomic number can be used. For example, the radiation sensitive semiconductor 11 is CdTe, CdMTe (wherein, M is Zn or Mn Im), CdZn _x Te _y1 Se _y2 (x + (y1 + y2) = 1), TlBr, YI ₂ (Y Is Hg or Pb), AlSb, PbSe or PbO.

The radiation-sensitive semiconductor 11 is not limited to this, and various kinds of semiconductors may be used. In another embodiment, the radiation-sensitive semiconductor 11 may be a IV-IV compound semiconductor such as SiC or a III-V compound semiconductor such as AlN, as well as a unit semiconductor such as Si or Ge. Such a semiconductor 11 can be advantageously used in a pn junction type, a PIN diode type (see FIG. 4), and a MOSFET structure.

1A, the first electrode 12 may be disposed on a lower surface of the semiconductor 11 to serve as a ground (GND) to the semiconductor 11. [ The second electrode (15) is disposed on the upper surface of the semiconductor (11) and collects charges generated by voltage application and radiation incidence.

As described above, in order to apply a voltage to the detecting element 10, one electrode may be grounded or connected to a low potential, and the other electrode may be connected to a relatively high potential. Since the electron mobility in the semiconductor 11 used for the radiation detecting element 10 is 10 times larger than the electron mobility of the holes, the electrode for collecting electrons is an electrode to which a high potential is applied, And the second electrode 15, which is an electrode on the opposite side of the grounded first electrode 12.

As described above, the radiation-sensitive semiconductor 11 has a high resistivity. Due to the relatively low work function of the metal electrode, a Schottky barrier is formed between the electrodes 12 and 15 and the semiconductor 11, Tends to be difficult to achieve.

In order to solve such a problem, in the present embodiment, a plurality of nanostructures 14 may be arranged on the surface of the semiconductor 11 on which the second electrode 15 for charge collection is formed. In the present embodiment, the arrangement of the nanostructures 14 is illustrated only at the interface between the semiconductor 11 and the second electrode 15, but in another embodiment, the semiconductor 11 and the first electrode 12).

2, the interface A between the semiconductor 11 and the second electrode 15 has a relatively high Schottky barrier due to an inadequate work function? _M of the electrode, The region B in which the nanostructure 14 is located can be lowered at the interface between the semiconductor 11 and the second electrode 15 due to a locally nano-sized structure (陸_{n1 ,} ? _N2 ). As a result, an inhomogeneous effective schottky barrier height is formed at the interface between the semiconductor 11 and the second electrode 15 due to the introduction of the nanostructure 14, Can be improved.

This effect can be understood as an effect of nano-sized particles irrespective of the kind of the substance of the nanostructure 14. As shown in FIG. 2, the effect of lowering the effective Schottky barrier may vary somewhat locally depending on the size of the nanostructure (Φ _{n1 ≠} Φ _n2 ). The size (d) of the nanostructure 14 usable in the present invention may be 100 nm or less, preferably 50 nm or less.

As the nanostructure 14 usable in the present invention, not only a conductive material such as a metal but also a semiconductor material and an electrically insulating material may be used.

In one example, when the nanostructure 14 is a metalloid such as a metal, an alloy, or a transparent conductive oxide, an electric field is concentrated around the nanostructure 14 due to surface plasmon resonance, Can be improved.

The nanostructure 14 may be formed of any one of B, Al, Ca, Sc, Ti, Fe, Co, Ni, Cu, Ge, Se, Sr, Ru, Rh, Pd, Ag, Te, Ba, A metal selected from the group consisting of Pt, Au, Tl, and Pb, or an alloy containing the same may be used. As the nano structure 14, a transparent conductive oxide such as selectively doped In ₂ O ₃ , SnO ₂ , ZnO, Cu-Oxide, NiO, and TiO ₂ may be used. For example, ITO (Sn-doped In ₂ O ₃ ) or AZO (Al-doped ZnO).

Depending on the constituent material of the nanostructure 14, the interface charge is increased by the interfacial reaction, thereby further improving the contact property of the interface. For example, when a metal such as Ag is used as the nanostructure 14, a solid solution of a compound semiconductor and a solid solution can be formed, and the charge can be increased near the interface of the semiconductor.

In another example, a semiconductor material or an electrically insulating material can be used as the nanostructure 14. In this way, when the high-resistance material is used, the charge collection efficiency can be improved by reducing the recombination speed at the interface through local passivation. Examples of the nanostructure 14 include ZrO ₂ , HfO ₂ , SiO ₂ , CeO ₂ , MgO, Insulating compounds such as Al ₂ O ₃ , SiN _x, and MgF ₂ may be used.

In a particular embodiment, the radiation sensitive semiconductor 11, CdTe, CdMTe (wherein, M is Zn or Mn Im), CdZn _x Te _y1 Se _y2 (x + (y1 + y2) = 1), TlBr, YI ₂ Au, Al, Cu, Pd, Pt, ITO, or AZO may be used as the nanostructure 14. In this case, the nanostructure 14 may be a high-resistance semiconductor such as AlGaN, Hg, or Pb (Y is Hg or Pb), AlSb, PbSe, And Ni, Cr, Ti, or Pt may be used as the second electrode 15. [ Preferably, the nanostructure 14 and the second electrode 15 may comprise Ag and Ni, respectively.

In addition, the semiconductor radiation detecting element can be used for a long time in a harsh environment, which may cause a polarization phenomenon in the detecting element. That is, the positive and negative ions of the constituent elements of the compound semiconductor are accumulated at the interface with the first and second electrodes 12 and 15, respectively, so that the internal electric field in the material / element can be weakened. In order to alleviate this problem, at least one of the first and second electrodes 12 and 15 may be formed by using a metal having a low electron affinity and a first ionization potential to suppress ion accumulation by an interfacial reaction have. As such an electrode material, Ca, Sr, Ti, Ba, Fe, Sc, B, Ta, Lu, Pb, and Tl may be used.

The nanostructure 14 employed in this embodiment can be formed through a subsequent heat treatment process after depositing a thin film of several to several tens of nanometers. The thin film deposition may be performed by thermal deposition, electron beam deposition, sputtering, pulse laser deposition, or the like, and the subsequent heat treatment may be performed by rapid thermal processing (RTP), laser annealing, electron beam irradiation, ion beam irradiation, or the like.

In certain embodiments, thin film growth can be achieved by nucleation followed by quenching before aggregation occurs to form the desired nanostructure. For example, such a nanostructure can be obtained when a thin film is grown with an effective thickness of 10 nm or less.

Fig. 3 is a schematic diagram showing a radiation measurement system with the semiconductor radiation detection element shown in Fig. 1b.

3 may include a semiconductor radiation detecting element 10, a high voltage power supply 22, a preamplifier 24, a main amplifier 26 and a processor /

The first electrode 12 of the semiconductor radiation detecting element 10 may be connected to the ground GND and the second electrode 15 may be connected to the high voltage power source 22 and the preamplifier 24. [ And a bias voltage is applied to the detection element by the high voltage power source 22. [ When a radiation such as a gamma ray is incident on the detecting element 10, an electron-hole can be generated in the radiation-sensitive semiconductor 11. These electron-holes are collected through the second electrode 15 by the bias voltage, and output to the preamplifier 24 a signal proportional to the intensity of the incident radiation. Here, the output signal is an analog signal in the form of a charge amount.

The radiation detecting element 10 according to the present embodiment changes the characteristics of the metal electrode-semiconductor material interface by introducing the arrangement of the nanostructures 14 between the semiconductor 11 and the second electrode 15 as described above So that the charge collection efficiency (electron collection efficiency in this embodiment) can be greatly improved.

The preamplifier 24 converts an analog signal in the form of a charge quantity output from the detecting element 10 into an analog signal of a voltage type which is comparatively easy to process the signal, first amplifies it, and outputs it to the main amplifier 26. The main amplifier 26 applies pulse shaping and secondary amplification to the output signal, and then outputs the resultant signal to the processor / display unit 27.

The processor / display unit 27 may convert the received signal into a digital signal and then store the digital signal. The processor / display unit 27 may analyze the digital signal and provide information such as a radiation intensity and a position through display means such as a display. The ADC (Analog to Digital Converter) may be included in the processor / display unit 27, but may be located at the front end of the processor / display unit 27 as necessary.

As described above, since the present radiation measurement system uses a semiconductor radiation detection element having improved charge collection efficiency through the introduction of nanoparticle array, it can not only improve the accuracy of radiation measurement, The amount of use can be reduced or replaced, which can dramatically reduce production costs.

4 is a side view showing a semiconductor radiation detecting element 30 according to another embodiment of the present invention.

The semiconductor radiation detecting element 30 shown in FIG. 4 includes first and second electrodes 32 and 35 disposed on opposite sides of the radiation-sensitive semiconductor 31 and the radiation-sensitive semiconductor 31, respectively .

The semiconductor radiation detecting element 30 according to the present embodiment may have a PIN diode structure. The semiconductor radiation detecting element 30 may be employed in an indirect structure in which radiation is incident through a scintillator.

The radiation-sensitive semiconductor 31 employed in this embodiment includes an n-type region 31b doped with intrinsic or low concentration, a high concentration p-type region 31c in contact with the first electrode 32, And may have a high concentration n-type region 31a in contact with the electrode 35.

Various types of semiconductors may be used for the radiation-sensitive semiconductor 31 as described in the above embodiments. For example, the radiation-sensitive semiconductor 31 may be not only a single-unit semiconductor such as Si or Ge but also a group IV-IV compound semiconductor such as SiC or a III-V group compound semiconductor such as AlN.

4, the first electrode 32 and the second electrode 35 apply or ground a low potential to the first electrode 32 to apply a voltage to the semiconductor 31 , A relatively high potential can be applied to the second electrode (35).

In this embodiment, the second electrode 35 may serve to collect the charge (e.g., electrons) generated by the radiation incidence. A plurality of nanostructures 34 may be arranged on the surface of the high-concentration n-type region 31a where the second electrode 35 for charge collection is formed. Due to the introduction of the nanostructure 34, the effective Schottky barrier height at the interface between the n-type region 31a and the second electrode 35 becomes inhomogeneous, and the ohmic contact characteristic of the interface can be improved. This effect can be understood as an effect of nano-sized particles irrespective of the kind of the material of the nanostructure 34. As the nanostructure 34 usable in the present invention, not only a conductive material such as a metal but also a semiconductor material and an electrically insulating material may be used. The size (d) of the nanostructure 34 may be 100 nm or less, preferably 50 nm or less.

Voltage is applied to the semiconductor 31 through the first electrode 32 and the second electrode 35. The radiation is incident on the depletion region D and charges are generated in proportion to the intensity of the incident radiation, And collected through the second electrode 35, and information such as the radiation intensity can be measured through the processing described in FIG.

As described above, according to the present invention, an arrangement of nanostructures such as various types of particles at an interface between an electrode and a semiconductor is introduced at the interface, whereby an inhomogeneous Schottky barrier is formed at the interface. As a result, The efficiency can be improved. In addition, when a high-resistance compound nanostructure is used, it is possible to further increase the charge collection efficiency by further reducing the interface recombination speed through local passivation. On the other hand, by using a metal having a low electron affinity or a low first ionization energy as the nanostructure, the polarization phenomenon can be mitigated and high reliability can be ensured even for a long time use of the semiconductor radiation detecting element.

The present invention is not limited by the above-described embodiments and the accompanying drawings, but is intended to be limited only by the appended claims. It will be apparent to those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims. something to do.

10, 30: Semiconductor radiation detecting element
11, 31: radiation-sensitive semiconductor
12, 32: first electrode
14, 34: Nano structure array
15, 35: second electrode
22: High voltage power source
24: Preamplifier
26: main amplifier
27: Processor / Display

Claims (10)

A radiation-sensitive semiconductor in which charges are generated by radiation incidence;
A first electrode disposed in a first region of the semiconductor and applying a voltage to the semiconductor;
A second electrode disposed in a second region of the semiconductor and collecting the generated charge; And
And a plurality of nanostructures arranged on a surface of at least one of the first and second regions.
The method according to claim 1,
Wherein the semiconductor has a resistivity of 10 ⁸ ? Cm or more.
3. The method of claim 2,
The semiconductor is CdTe, CdMTe (wherein, M is Zn or Mn _{Im), CdZn x Te y1 Se y2} (x + (y1 + y2) = 1), TlBr, YI 2 (Y is Hg or Pb Im), AlSb, PbSe And PbO. ≪ / RTI >
4. The method according to any one of claims 1 to 3,
And the arrangement of the nanostructure is located at an interface between the second electrode and the second region of the semiconductor.
5. The method of claim 4,
Wherein the nanostructure comprises at least one selected from the group consisting of Ag, Au, Al, Cu, Pd, Pt, Sn-doped In ₂ O ₃ and AZO,
Wherein the second electrode comprises at least one selected from the group consisting of Ni, Cr, Ti and Pt.
The method according to claim 1,
Wherein the nanostructure has a size of 100 nm or less.
The method according to claim 1,
Wherein the nanostructure is formed of a material selected from the group consisting of B, Al, Ca, Sc, Ti, Fe, Co, Ni, Cu, Ge, Se, Sr, Ru, Rh, Pd, Ag, Te, Ba, Lu, Ta, Tl, and Pb, or an alloy containing the same.
The method according to claim 1,
Wherein the nanostructure is a transparent conductive oxide.
9. The method of claim 8,
Wherein the nanostructure comprises at least one oxide selected from the group consisting of selectively doped In ₂ O ₃ , SnO ₂ , ZnO, Cu-Oxide, NiO, and TiO ₂ .
The method according to claim 1,
The nanostructure may include at least one of ZrO ₂ , HfO ₂ , SiO ₂ , CeO ₂ , MgO, At least one insulating compound selected from the group consisting of Al ₂ O ₃ , SiN _x, and MgF ₂ .

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