EP0504603A1 - Dispositif semiconducteur émetteur d'électrons - Google Patents

Dispositif semiconducteur émetteur d'électrons Download PDF

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Publication number
EP0504603A1
EP0504603A1 EP92102746A EP92102746A EP0504603A1 EP 0504603 A1 EP0504603 A1 EP 0504603A1 EP 92102746 A EP92102746 A EP 92102746A EP 92102746 A EP92102746 A EP 92102746A EP 0504603 A1 EP0504603 A1 EP 0504603A1
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Prior art keywords
type semiconductor
electron emission
semiconductor region
emission device
region
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EP92102746A
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German (de)
English (en)
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EP0504603B1 (fr
Inventor
Nobuo C/O Canon Kabushiki Kaisha Watanabe
Norio C/O Canon Kabushiki Kaisha Kaneko
Masahiko C/O Canon Kabushiki Kaisha Okunuki
Takeo C/O Canon Kabushiki Kaisha Tsukamoto
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Canon Inc
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Canon Inc
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Priority claimed from JP4557991A external-priority patent/JP3135070B2/ja
Priority claimed from JP5559791A external-priority patent/JP3137267B2/ja
Priority claimed from JP23445791A external-priority patent/JPH0574331A/ja
Priority claimed from JP23445691A external-priority patent/JPH0574330A/ja
Application filed by Canon Inc filed Critical Canon Inc
Publication of EP0504603A1 publication Critical patent/EP0504603A1/fr
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    • H—ELECTRICITY
    • H01—ELECTRIC ELEMENTS
    • H01J—ELECTRIC DISCHARGE TUBES OR DISCHARGE LAMPS
    • H01J1/00—Details of electrodes, of magnetic control means, of screens, or of the mounting or spacing thereof, common to two or more basic types of discharge tubes or lamps
    • H01J1/02—Main electrodes
    • H01J1/30—Cold cathodes, e.g. field-emissive cathode
    • H01J1/308—Semiconductor cathodes, e.g. cathodes with PN junction layers

Definitions

  • the present invention relates to a semiconductor electron emission device having a Schottky barrier junction on the surface of a p-type semiconductor which is a substrate, and a high density p-type semiconductor region bringing about the avalanche amplification within the p-type semiconductor under an electrode forming the Schottky barrier junction.
  • Such a semiconductor electron emission device is one in which an electron emission portion is fabricated by forming a p-type semiconductor layer and an n-type semiconductor layer on a semiconductor substrate, and depositing cesium on the surface of the n-type semiconductor layer to have a decreased work function of the surface. And a reverse bias voltage is applied across a pn junction formed of the p-type semiconductor layer and the n-type semiconductor layer to cause the avalanche breakdown to make hot electrons, and emit the electrons from the electron emission portion in a direction perpendicular to the surface of the semiconductor substrate.
  • a semiconductor electron emission device in which a Schottky barrier junction is formed of the p-type semiconductor and a metal material, or the p-type semiconductor and a metallic compound, and a reverse bias voltage is applied across the Schottky barrier junction to cause the avalanche breakdown to make hot electrons and emit the electrons from the electron emission portion in a direction perpendicular to the surface of the semiconductor substrate, as described in Japanese Laid-Open Patent Application No. 1-220328.
  • the avalanche breakdown is caused in the high density p-type semiconductor region where the depletion layer width is formed thinnest, so that electrons having high energy produced therein are emitted from a solid surface to the outside.
  • the shape of the depletion layer around the pn junction or Schottky barrier junction has a radius of curvature determined by a carrier density of semiconductor and an applied voltage, and the electric field is more concentrated on the depletion layer than in other regions. Accordingly, the breakdown or leakage of the current around the depletion layer may occur at a lower applied voltage than if the avalanche breakdown occurs in the high density p-type semiconductor region intrinsically required, so that the device characteristics may be deteriorated.
  • the electron emission device having the pn junction or Schottky barrier junction, it is possible to increase the radius of curvature around the depletion layer with a decreased carrier density of the p-type semiconductor around the high density p-type semiconductor region where the avalanche breakdown occurs, thereby preventing the breakdown at the lower voltage, but the electrical resistance between an electrode for supplying carriers and the high density p-type semiconductor region where the avalanche breakdown occurs may increase, causing the operating voltage of device to rise, and a problem with the deterioration of device may occur due to the Joule heating.
  • a guard ring structure of high density n-type semiconductor was formed, concentrically with the high density p-type semiconductor region, within the p-type semiconductor region.
  • the depletion layer was formed continuously from the high density p-type semiconductor region outward to the p-type semiconductor region and the high density n-type semiconductor layer so as to have a large radius of curvature in the most outside region, thereby preventing the breakdown or the leakage of current around the depletion layer.
  • a manufacturing process such as the ion injection or the thermal diffusion for forming the ring-like n-type semiconductor region (guard ring structure) at a high density, or a process for forming the ohmic junction electrode to apply the voltage to the guard ring of the high density n-type semiconductor is necessary, in which there is a problem that the manufacturing process is complex.
  • the conventional semiconductor electron emission device it is required to supply electrons sufficiently to the high density p-type semiconductor region defining the avalanche amplification, when emitting electrons produced by the avalanche amplification mechanism.
  • the high density p-type semiconductor region is surrounded by the p-type semiconductor region having a high resistivity, and thus spaced away from the semiconductor or metallic electrode having a low resistivity for supplying electrons.
  • the current is concentrated in the high density p-type semiconductor region and the neighborhood thereof, so that the Joule heat is generated in the region having a high resistance, and it was difficult to prevent the breakage or deterioration of device due to the temperature elevation, or the fluctuation in the emission amount of electrons.
  • the present invention was achieved in the light of the problems associated with the conventional arts as above described, and aimed to provide a smaller semiconductor electron emission device in which the device structure and the manufacturing process can be simplified, and a higher speed of device in the operation can be attained.
  • Another object of the present invention is to resolve the above-mentioned conventional problems and provide a semiconductor electron emission device having a high operating speed and with reduced heat generation due to the Joule heating within the device.
  • a semiconductor electron emission device having an electron emission portion comprised of a Schottky barrier junction between a metallic material or metallic compound material and a semiconductor for emitting electrons from a solid surface, firstly characterized in that the electron emission portion comprising: a first p-type semiconductor region bringing about the avalanche breakdown by forming the Schottky barrier junction; a second p-type semiconductor region adjacent to the first p-type semiconductor region for supplying carriers to the first p-type semiconductor region; and an n-type semiconductor region, located around the first p-type semiconductor region, for forming the Schottky barrier junction with the metal material or metallic compound material as well as forming a pn junction with the first p-type semiconductor region; wherein the density relation between carrier densities in the first and second p-type semiconductor regions and the n-type semiconductor region, (first p-type semiconductor region) > (second p-type semiconductor region) > (n-type semiconductor region) or (second p-type semiconductor
  • a semiconductor electron emission device having an electron emission portion comprised of a pn junction between an n-type semiconductor and a p-type semiconductor for emitting electrons from a solid surface, secondly characterized in that the electron emission portion comprising: a first n-type semiconductor region located on the solid surface, and a first p-type semiconductor region bringing about the avalanche breakdown by forming the pn Junction with the first n-type semiconductor region; a second p-type semiconductor region adjacent to the first p-type semiconductor region for supplying carriers to the first p-type semiconductor region; and a second n-type semiconductor region, located around the first p-type semiconductor region, for forming the pn junction with the first p-type semiconductor region; wherein the density relation between carrier densities in the first and second p-type semiconductor regions and the first and second n-type semiconductor regions, (first n-type semiconductor region) > (first p-type semiconductor region) > (second p-type semiconductor region
  • a semiconductor electron emission device having an electron emission portion comprised of a Schottky barrier junction between a metal material or metallic compound material and a semiconductor for emitting electrons from a solid surface, thirdly characterized in that the electron emission portion comprising: a first p-type semiconductor region bringing about the avalanche breakdown by forming the Schottky barrier junction; a second p-type semiconductor region located around the first p-type semiconductor region; a third p-type semiconductor region located around the second p-type semiconductor region; and a fourth p-type semiconductor region for supplying carriers to the first p-type semiconductor region; wherein the density relation between carrier densities in the first to fourth p-type semiconductor regions, (first p-type semiconductor region) > (fourth p-type semiconductor region) > (second p-type semiconductor region) > (third p-type semiconductor region) or (fourth p-type semiconductor region) ⁇ (first p-type semiconductor region) > (second p-type semiconductor region)
  • a semiconductor electron emission device having an electron emission portion comprised of a pn junction between an n-type semiconductor and a p-type semiconductor for emitting electrons from a solid surface, fourthly characterized in that the electron emission portion comprising: an n-type semiconductor region located on the solid surface, and a first p-type semiconductor region bringing about the avalanche breakdown by forming the pn junction with the n-type semiconductor region; a second p-type semiconductor region located around the first p-type semiconductor region; a third p-type semiconductor region located around the second p-type semiconductor region; and a fourth p-type semiconductor region for supplying carriers to the first p-type semiconductor region; wherein the density relation between carrier densities in the first to fourth p-type semiconductor regions and the n-type semiconductor region, (n-type semiconductor region) > (first p-type semiconductor region) > (fourth p-type semiconductor region) > (second p-type semiconductor region) > (third p
  • a semiconductor electron emission device having a Schottky barrier junction on the surface of a p-type semiconductor which is a substrate, and a high density p-type semiconductor region bringing about the avalanche amplification within the p-type semiconductor under an electrode forming the Schottky barrier junction, fifthly characterized by comprising an electrode for applying the voltage to the Schottky barrier junction electrode on a surface of the high density p-type semiconductor region different from the surface on which the Schottky barrier junction is formed.
  • a semiconductor electron emission device having a Schottky barrier junction on the surface of a p-type semiconductor which is a substrate, and a high density p-type semiconductor region bringing about the avalanche amplification within the p-type semiconductor under an electrode forming the Schottky barrier junction, sixthly characterized by comprising a region located in the vicinity of the high density p-type semiconductor region, not in contact with the electrode for forming the Schottky barrier junction, and having a smaller resistivity than the p-type semiconductor.
  • Fig. 1 is a cross-sectional view showing a first example of a semiconductor electron emission device according to the present invention.
  • Fig. 2 is a view showing one example of an energy band for the semiconductor electron emission device of Schottky barrier junction.
  • Fig. 3 is a diagram showing one example of the current-voltage characteristics for the semiconductor electron emission device according to the present invention.
  • Fig. 4 is a diagram showing another example of the current-voltage characteristics for the semiconductor electron emission device according to the present invention.
  • Fig. 5 is a cross-sectional view showing a second example of a semiconductor electron emission device according to the present invention.
  • Figs. 6A and 6B are cross-sectional views showing a third example of a semiconductor electron emission device according to the present invention.
  • Fig. 7 is a cross-sectional view showing a fourth example of a semiconductor electron emission device according to the present invention.
  • Fig. 8 is a cross-sectional view showing a fifth example of a semiconductor electron emission device according to the present invention.
  • Figs. 9A and 9B are cross-sectional views showing a sixth example of a semiconductor electron emission deivce according to the present invention.
  • Fig. 10 is a plan view showing a semiconductor electron emission device in the example of the present invention.
  • Fig. 11 is a cross-sectional view taken along the line A-A' of Fig. 10.
  • Fig. 12 is a band diagram for explaining the operation principle of a device according to the present invention.
  • Fig. 13 is a plan view showing a part of multiple electron emission having semiconductor electron emission devices arranged like the matrix in the example of the present invention.
  • Fig. 14 is a cross-sectional view taken along the line A-A' of Fig. 13.
  • Figs. 15A and 15B schematically show a semiconductor electron emission device in the example of the present invention
  • Fig. 15A is a plan view
  • Fig. 15B is a cross-sectional view taken along the line A-A' of Fig. 15A.
  • Figs. 16A and 16B schematically show a semiconductor electron emission device using the pn junction of GaAs semiconductor in the example of the present invention
  • Fig. 16A is a plan view
  • Fig. 16B is a cross-sectional view taken along the line A-A' of Fig. 16A.
  • Figs. 17A and 17B show the state in which multiple semi-conductor electron emission devices in the example of the present invention are arranged
  • Fig. 17A is a plan view
  • Fig. 17B is a cross-sectional view taken along the line A-A' of Fig. 17A.
  • a second p-type semiconductor region having a lower carrier density and a third p-type semiconductor region having a further lower carrier density are formed around a first p-type semiconductor region of high density bringing about the avalanche breakdown.
  • a depletion layer the shape of which is thinnest in the first p-type semiconductor region so that the electric field is likely to be concentrated thereon. Accordingly, it is possible to bring about the avalanche breakdown efficiently only in the first p-type semiconductor region.
  • the series resistance value of semiconductor electron emission devices can be decreased by using the fourth p-type semiconductor region having a higher carrier density than the second p-type semiconductor region as the passage for the supply of carriers to the first p-type semiconductor region.
  • Fig. 1 is a cross-sectional view showing a semiconductor electron emission device of Schottky barrier junction type in the first example of the present invention.
  • the semiconductor electron emission device in this example is a Schottky barrier junction device in which a cylindrical high density p-type semiconductor region 105 which is a first p-type semiconductor region and a p-type semiconductor region 104, which is a fourth p-type semiconductor region, for supplying carriers to the high density p-type semiconductor region 105 are disposed in contact with each other on a substantial central portion of a high density p-type semiconductor substrate 101, a p-type semiconductor region 103 which is a second p-type semiconductor region and a low density p-type semiconductor region 102 which is a third p-type semiconductor region are disposed concentrically outwardly around the high density p-type semiconductor region 105 and the p-type semiconductor region 104, and a Schottky electrode 108 which is a metallic film for forming the Schottky barrier junction with the high density p-type semiconductor region 105 is disposed on the surface of the device.
  • the semiconductor electron emission device in this example is provided with an ohmic junction electrode 106 to the high density p-type semiconductor substrate 101 and an electrode wiring 109 to the Schottky electrode 108 for applying a reverse voltage to the Schottky barrier junction, the reverse voltage being applied from a power source 110.
  • the electrode wiring 109 is in contact with the Schottky electrode 108 on an insulating film 107 formed on the low density p-type semiconductor region 102 in order to prevent the short circuit with each p-type semiconductor region as previously described.
  • 111 shows the shape of a depletion layer end in a state where the reverse voltage is applied
  • 112 shows a region where the avalanche breakdown occurs with the application of the reverse voltage.
  • the bottom Ec of a conduction band for the p-type semiconductor is at a higher energy level than the vacuum level E VAC for the metal electrode forming the Schottky barrier, so that the avalanche breakdown is brought about.
  • An electron produced by the avalanche breakdown obtains a higher energy than the lattice temperature with the electric field within a depletion layer produced at an interface between semiconductor and metal electrode, and injected from the p-type semiconductor into the metal electrode forming the Schottky barrier junction.
  • the electron having a greater energy than the work function on the surface of metal electrode forming the Schottky barrier junction is discharged into the vacuum. Accordingly, the treatment for the surface of metal electrode to have a lower work function leads to an increase in the emission amount of electrons, as previously described.
  • FIG. 1 A manufacturing process of the semiconductor electron emission device as shown in Fig. 1 will be described specifically by way of an example.
  • the semiconductor electron emission device thus fabricated was installed within a vacuum chamber within which the degree of vacuum was retained at about 1x10 ⁇ 7Torr, and a voltage of 7V was applied between the ohmic junction electrode 106 and the electrode wiring 109 from a power source 110, so that the electron emisson of about 15pA was observed from the surface of the Schottky electrode 108 above the high density p-type semiconductor region 105. If the applied voltage (device voltage) was sequentially increased up to 10V, the electron emission amount (emission current) was sequentially increased up to about 100pA, as shown in Fig. 3.
  • a depletion layer 111 spreads about 0.04 ⁇ m beyond a Schottky barrier interface with the Schottky electrode 108 in the high density p-type semiconductor region 105, when this device voltage is applied.
  • the electric field is most concentrated on an avalanche region 112 of the high density p-type semiconductor region 105, in which region the avalanche breakdown occurs most efficiently.
  • a semiconductor electron emission device which was fabricated by changing only the Be density of the p-type semiconductor region 104 which is a fourth p-type semiconductor region for supplying carriers to the high density p-type semiconductor region 105 which is a first p-type semiconductor region to 3x1018cm ⁇ 3 in the fabrication conditions as above described, was installed within the same vacuum chamber. If a device voltage of 5V was applied to the semiconductor electron emission device from the power source 110, the electron emission (emission current) of about 20pA was observed from the surface of the Schottky electrode 108 above the high density p-type semiconductor region 105. If the device voltage was sequentially increased up to 7V, the emission current was also sequentially increased up to about 100pA.
  • GaAs was used as the semiconductor, but other semiconductor materials such as Si, Ge, GaP, AlAs, GaAsP, AlGaAs, SiC, BP, AlN, or diamond are applicable in principle, and particularly, the material of indirect transition type and having a wide band gap is preferable.
  • the semi-insulating region can be fabricated by the use of various endogenic defects or residual impurities within the crystal, and purposely added compensating impurities. When this semi-insulating region is formed, undoped crystal not containing the dopant is also applicable because of its semi-insulating property.
  • the material for the ohmic junction electrode 106 requires to form the Schottky junction with the p-type semiconductor, and may be, for example, Al, Au or LaB6, in addition to tungsten (W), as commonly well known.
  • W tungsten
  • the electron emission efficiency can be increased by coating a material of low work function such as Cs on the surface, when the work function of the material is large.
  • Fig. 5 is a cross-sectional view showing a semiconductor electron emission device of pn junction type in the second example of the present invention.
  • the semiconductor electron emission device in this example is a pn junction device having an electron emission portion in which a cylindrical high density p-type semiconductor region 505 which is a first p-type semiconductor region and a p-type semiconductor region 504, which is a fourth p-type semiconductor region, for supplying carriers to the high density p-type semiconductor region 505 are disposed in contact with each other on a substantial central portion of a high density p-type semiconductor substrate 501, and a p-type semiconductor region 503 which is a second p-type semiconductor region and a low density p-type semiconductor region 502 which is a third p-type semiconductor region are disposed concentrically outwardly around the high density p-type semiconductor region 505 and the p-type semiconductor region 504, and a high density n-type semiconductor region 506 which is an n-type semiconductor region for forming the pn junction with the high density p-type semiconductor region 505 is disposed thereon.
  • the semiconductor electron emission device in this example is provided with an ohmic junction electrode 507 to the high density p-type semiconductor substrate 501, an ohmic junction electrode 509 to the high density n-type semiconductor region 506, and a low work function coating 510 formed on the high density n-type semiconductor region 506, for applying a reverse voltage to the pn junction, the reverse voltage being applied from a power source 511.
  • the ohmic junction electrode 509 is in contact with the high density n-type semiconductor region 506 via an insulating film 508 formed along an edge portion of the surface on the low density p-type semiconductor region 502 in order to prevent the short circuit with the low density p-type semiconductor region 502.
  • 512 shows the shape of a depletion layer end in a state where the reverse voltage is applied
  • 513 shows a region where the avalanche breakdown occurs with the application of the reverse voltage.
  • a manufacturing process of the semiconductor electron emission device of pn junction type will be described specifically by way of an example.
  • the semiconductor electron emission device thus fabricated was installed within a vacuum chamber which was retained at about 1x10 ⁇ 11Torr or less, and a device voltage of 6V was applied between the ohmic junction electrodes 507 and 509 from the power source 511, so that the electron emission of about 0.1 ⁇ A was observed from the surface of the low work function coating 510 (Cs) above the high density p-type semiconductor region 505.
  • a device voltage of 6V was applied between the ohmic junction electrodes 507 and 509 from the power source 511, so that the electron emission of about 0.1 ⁇ A was observed from the surface of the low work function coating 510 (Cs) above the high density p-type semiconductor region 505.
  • Fig. 6 is a view showing a multi semiconductor electron emission device of Schottky barrier type provided with a plurality of electron emission portions, in a third example of the present invention, in which Fig. 6A is a plan view thereof, and Fig. 6B is a cross-sectional view taken along the line A-A' of Fig. 6A.
  • the multi semiconductor electron emission device of this example is provided with four electron emission portions 600A, 600B, 600C and 600D, like a matrix, on a high density p-type semiconductor region 602 formed on a semiconductor substrate 601.
  • the electron emission portion 600A Since the electron emission portions 600A, 600B, 600C and 600D all have the same constitution, the electron emission portion 600A will be exemplified.
  • the electron emission portion 600A has the same constitution as in the previous first example, comprising a high density p-type semiconductor region 606A which is a first p-type semiconductor region, a p-type semiconductor region 605A which is a fourth p-type semiconductor region disposed in contact with the high density p-type semiconductor region 606A for supplying carriers to the high density p-type semiconductor region 606A, a p-type semiconductor region 604A which is a second p-type semiconductor region located around the high density p-type semiconductor region 606A and the p-type semiconductor region 605A, a low density p-type semiconductor region 603 which is a third p-type semiconductor region located around the p-type semiconductor region 604A, and a Schottky electrode 611A for forming the Schottky barrier junction with the high density p-type semiconductor region 606A.
  • the electrode wiring 610A is in contact with the Schottky electrode 611A on an insulating film 608 formed on the low density p-type semiconductor region 603 in order to prevent the short circuit with each p-type semiconductor region as previously described.
  • the ohmic junction electrode 609 is connected via the high density p-type semiconductor region 607 to the high density p-type semiconductor region 602, and in this example, provided at two positions as shown in Fig. 6A.
  • This ohmic junction electrode 609 is a common electrode to the four electron emission portions 600A, 600B, 600C and 600D.
  • the Schottky electrode 611A may be connected in common with Schottky electrodes 611B, 611C and 611D (611C, 611D are not shown) of other electron emission portions 600B, 600C and 600D, in which case as the ohmic junction electrode 609 is commonly used, the four electron emission portions 600A, 600B, 600C and 600D are controlled simultaneously for the electron emission operation.
  • the Schottky electrodes 611A, 611B, 611C and 611D of the electron emission portions 600A, 600B, 600C and 600D are independent of each other, the control for each electron emission portion 600A, 600B, 600C and 600D is allowed.
  • the portion except for the ohmic junction electrode 609 is covered via a supporting member 612 made of insulating material with a gate 613 composed of metallic film provided on the insulating layer 608.
  • This gate 613 is formed with opening portions 614A, 614B, 614C and 614D at positions corresponding to and upward of the electron emission portions 600A, 600B, 600C and 600D, respectively, whereby electrons emitted from each electron emission portion 600A, 600B, 600C and 600D are passed through the opening portions 614A, 614B, 614C and 614D outward.
  • a manufacturing process of the multi semiconductor electron emission device will be described specifically by way of an example.
  • the multi semiconductor electron emission device having the four electron emission portions 600A, 600B, 600C, 600D was completed.
  • a multi semiconductor electron emission device having the electron emission portions arranged like a matrix, 20 in the X direction, and 10 in the Y direction, was fabricated, and installed within a vacuum chamber within which the degree of vacuum was at about 1x10 ⁇ 7Torr. If a reverse voltage of 7V was applied to the entire area of the electron emission portions, the electron emission of about 20nA in total was observed. Also, by applying a reverse voltage only between arbitrary ohmic junction electrode 609 and arbitrary electrode wiring 610, it was observed that only device located at its intersection emitted electrons. In this way, with this example, it is possible to form an electron emission device having the same electron emission characteristics as a conventional multi semiconductor electron emission device and simply fabricated.
  • the n-type semiconductor region having a low carrier density is formed around a first p-type semiconductor region having a high density bringing about the avalanche breakdown.
  • the second p-type semiconductor region as the passage of supplying carriers to the first p-type semiconductor region, it is possible to make the series resistance of device an appropriate value. Accordingly, the operating speed can be increased.
  • Fig. 7 is a cross-sectional view showing a semiconductor electron emission device of Schottky barrier junction type in the fourth example of the present invention.
  • the semiconductor electron emission device in this example is a Schottky barrier junction device in which a cylindrical high density p-type semiconductor region 703 which is a first p-type semiconductor region and a p-type semiconductor region 704, which is a second p-type semiconductor region, for supplying carriers to the high density p-type semiconductor region 703 are disposed in contact with each other on a substantial central portion of a high density p-type semiconductor substrate 701, a low density n-type semiconductor region 702 which is an n-type semiconductor region is disposed concentrically outwardly around the high density p-type semiconductor region 703 and the p-type semiconductor legion 704, and a Schottky electrode 708 which is a metallic film for forming the Schottky barrier junction with the high density p-type semiconductor region 703 is disposed on the surface of the device.
  • the semiconductor electron emission device in this example is provided with an ohmic junction electrode 706 to the high density p-type semiconductor substrate 701 and an electrode wiring 707 to the Schottky electrode 708 for applying a reverse voltage to the Schottky barrier junction, the reverse voltage being applied from a power source 709.
  • the electrode wiring 707 is in contact with the Schottky electrode 708 on an insulating film 705 formed on the low density n-type semiconductor region 702 in order to prevent the short circuit with each p-type semiconductor region as previously described.
  • 710 shows the shape of a depletion layer end in a state where the reverse voltage is applied.
  • the electron emission process in the semiconductor electron emission device using the Schottky barrier junction of the present invention is the same as described in Fig. 2.
  • a manufacturing process of the semiconductor electron emission device as shown in Fig. 7 will be described specifically by way of an example.
  • the semiconductor electron emission device thus fabricated was installed within a vacuum chamber within which the degree of vacuum was retained at about 1x10 ⁇ 7Torr, and a voltage of 7V was applied between the ohmic junction electrode 706 and the electrode wiring 709 from a power source 709, so that the electron emission of about 15pA was observed from the surface of the Schottky electrode 708 above the high density p-type semiconductor region 703. If the applied voltage (device voltage) was sequentially increased up to 10V, the electron emission amount (emission current) was also sequentially increased up to about 100pA, as shown in Fig. 3.
  • a depletion layer 710 spreads about 0.04 ⁇ m beyond a Schottky barrier interface with the Schottky electrode 708 in the high density p-type semiconductor region 703, when this device voltage is applied.
  • the electric field is most concentrated on a portion of the high density p-type semiconductor region 703, in which region the avalanche breakdown occurs efficiently.
  • a semiconductor electron emission device fabricated by changing only the Be density of the p-type semiconductor region 704 which is a second p-type semiconductor region for supplying carriers to the high density p-type semiconductor region 703 which is a first p-type semiconductor region to 3x1018cm ⁇ 3 in the fabrication conditions as above described, was installed within the same vacuum chamber. If a device voltage of 5V was applied to the semiconductor electron emission device from the power source 709, the electron emission (emission current) of about 20pA was observed from the surface of the Schottky electrode 708 above the high density p-type semiconductor region 703. If the device voltage was sequentially increased up to 7V, the emission current was also sequentially increased up to about 100pA.
  • GaAs was used as the semiconductor, but other semiconductor materials such as Si, Ge, GaP, AlAs, GaAsP, AlGaAs, SiC, BP, AlN, or diamond are applicable in principle, and particularly, the material of indirect transition type and having a wide band gap is preferable.
  • the material for the ohmic junction electrode 706 requires to form the Schottky barrier junction with the p-type semiconductor, and may be, for example, Al, Au or LaB6, in addition to tungsten (W), as commonly well known.
  • W tungsten
  • the electron emission efficiency increases with smaller work function of the electrode surface, as previously described, the electron emission efficiency can be increased by coating a material of low work function such as Cs on the surface, when the work function of the material is large.
  • Fig. 8 is a cross-sectional view showing a semiconductor electron emission device of pn junction type in the fifth example of the present invention.
  • the semiconductor electron emission device in this example is a pn junction device having an electron emission portion in which a cylindrical high density p-type semiconductor region 803 which is a first p-type semiconductor region and a p-type semiconductor region 804, which is a second p-type semiconductor region, for supplying carriers to the high density p-type semiconductor region 803 are disposed in contact with each other on a substantial central portion of a high density p-type semiconductor substrate 801, a low density n-type semiconductor region 802 which is a second n-type semiconductor region is disposed concentrically outwardly around the high density p-type semiconductor region 803 and the p-type semiconductor region 804, and a high density n-type semiconductor region 805 which is a first n-type semiconductor region for forming the pn junction with the high density p-type semiconductor region 803 is disposed thereon.
  • the semiconductor electron emission device in this example is provided with an ohmic junction electrode 807 to the high density p-type semiconductor substrate 801, an ohmic junction electrode 808 to the high density n-type semiconductor region 805, and a low work function coating 809 formed on the high density n-type semiconductor region 805, for applying a reverse voltage to the pn junction, the reverse voltage being applied from a power source 810.
  • the ohmic junction electrode 808 is in contact with the high density n-type semiconductor region 805 via an insulating film 806 formed along an edge portion of the surface on the low density p-type semiconductor region 802 in order to prevent the short circuit with the low density n-type semiconductor region 802.
  • 811 shows the shape of a depletion layer end in a state where the reverse voltage is applied.
  • a manufacturing process of the semiconductor electron emission device of pn junction type will be described specifically by way of an example.
  • the semiconductor electron emission device thus fabricated was installed within a vacuum chamber which was retained at about 1x10 ⁇ 11Torr or less, and a device voltage of 6V was applied between the ohmic junction electrodes 807 and 808 from the power source 810, so that the electron emission of about 0.1 ⁇ A was observed from the surface of the low work function coating 809 (Cs) above the high density n-type semiconductor region 805.
  • a device voltage of 6V was applied between the ohmic junction electrodes 807 and 808 from the power source 810, so that the electron emission of about 0.1 ⁇ A was observed from the surface of the low work function coating 809 (Cs) above the high density n-type semiconductor region 805.
  • Fig. 9 is a view showing a multi semiconductor electron emission device of Schottky barrier type provided with a plurality of electron emission portions, in a sixth example of the present invention, in which (a) is a plan view thereof, and (b) is a cross-sectional view taken along the line A-A' of (a).
  • the multi semiconductor electron emission device of this example is provided with four electron emission portions 900A, 900B, 900C and 900D, like a matrix, on a high density p-type semiconductor region 902 formed on a semiconductor substrate 901.
  • the electron emission portion 900A Since the electron emission portions 900A, 900B, 900C and 900D all have the same constitution, the electron emission portion 900A will be exemplified.
  • the electron emission portion 900A has the same constitution as in the previous fourth example, comprising a high density p-type semiconductor region 904A which is a first p-type semiconductor region, a p-type semiconductor region 905A which is a second p-type semiconductor region disposed in contact with the high density p-type semiconductor region 904A for supplying carriers to the high density p-type semiconductor region 904A, a low density n-type semiconductor region 903 which is a n-type semiconductor region located around the high density p-type semiconductor region 904A and the p-type semiconductor region 905A, and a Schottky electrode 910A for forming the Schottky barrier junction with the high density p-type semiconductor region 904A.
  • the electrode wiring 909A is in contact with the Schottky electrode 910A on an insulating film 907 formed on the low density n-type semiconductor region 903 in order to prevent the short circuit with each p-type semiconductor region as previously described.
  • the ohmic junction electrode 908 is connected via the high density p-type semiconductor region 906 to the high density p-type semiconductor region 902, and in this example, provided at two positions as shown in Fig. 9A.
  • This ohmic junction electrode 908 is a common electrode to the four electron emission portions 900A, 900B, 900C and 900D.
  • the Schottky electrode 910A may be connected in common with Schottky electrodes 910B, 910C and 910D (910C, 910D are not shown) of other electron emission portions 900B, 900C and 900D, in which case as the ohmic junction electrode 908 is commonly used, the four electron emission portions 900A, 900B, 900C and 900D are controlled simultaneously for the electron emission operation.
  • the Schottky electrodes 910A, 910B, 910C and 910D of the electron emission portions 900A, 900B, 900C and 900D are independent of each other, the control for each electron emission portion 900A, 900B, 900C and 900D is allowed.
  • the portion except for the ohmic junction electrode 908 is covered via a supporting member 911 made of insulating material with a gate 912 composed of metallic film provided on the insulating layer 907.
  • This gate 912 is formed with opening portions 913A, 913B, 913C and 913D at positions corresponding to and upward of the electron emission portions 900A, 900B, 900C and 900D, respectively, whereby electrons emitted from each electron emission portion 900A, 900B, 900C and 900D are passed through the opening portions 913A, 913B, 913C and 913D outward.
  • a manufacturing process of the multi semiconductor electron emission device will be described specifically by way of an example.
  • the multi semiconductor electron emission device having the four electron emission portions 900A, 900B, 900C, 900D were completed.
  • a multi semiconductor electron emission device having the electron emission portions arranged like a matrix, 20 in the X direction, and 10 in the Y direction, was fabricated, and installed within a vacuum chamber within which the degree of vacuum was at about 1x10 ⁇ 7Torr. If a reverse voltage of 7V was applied to the entire area of the electron emission portions, the electron emission of about 20nA in total was observed. Also, by applying a reverse voltage only between arbitrary ohmic junction electrode 908 and arbitrary electrode wiring 909, it was observed that only device located at its intersection emitted electrons. In this way, with this example, it is possible to form an electron emission device having the same electron emission characteristics as a conventional multi semiconductor electron emission device and simply fabricated.
  • the present invention it is possible to make faster the operating speed of the device by providing the region of small resistivity in the vicinity of the high density p-type semiconductor region bringing about the avalanche breakdown. Further, it is possible to avoid the breakage or deterioration of the device due to the Joule heating in the vicinity of the high density p-type semiconductor region bringing about the avalanche breakdown, and reduce the fluctuation in the electron emission amount.
  • Figs. 10 and 11 are schematic views showing a semiconductor electron emission device in one example of the present invention.
  • Fig. 10 is a plan view thereof, and Fig. 11 is a cross-sectional view taken along the line A-A' of Fig. 10.
  • 1001 is a high density p-type semiconductor substrate
  • 1002 is a p-type semiconductor layer
  • 1003 is a high density p-type semiconductor region which is a feature of the present invention
  • 1004 is a p-type semiconductor layer
  • 1005 is a ring-like n-type semiconductor region
  • 1006 is a high density p-type semiconductor region bringing about the avalanche amplification
  • 1007 is an insulating film
  • 1008, 1009 are ohmic junction electrodes, respectively
  • 1010 is a metallic electrode which is a Schottky barrier junction
  • 1011 is an end of a depletion layer when a reverse voltage calculated is applied
  • 1012 is a power source.
  • the semiconductor electron emission device thus fabricated was installed within a vacuum chamber which was retained at a vacuum of about 1x10 ⁇ 7Torr, and when a reverse voltage of 5V was applied from the power source 1011, the electron emission of about 0.1nA was observed from the W surface above the high density p-type semiconductor region 1006, and when the applied voltage was further increased up to 10V, the electron emission of about lnA was observed. However, the breakage or unstable emission current during the electron emission, which occurred with a conventional device, was not observed.
  • the semiconductor electron emission device realized the fast driving so that the operating speed from the application of electrons to their emission was about 1/4 or less that of the conventional device not having the high density p-type semiconductor region (which was a region having a small resistivity) of the present invention, when the structure and the size were the same.
  • the factor of determining the operating speed of the device depends on the product RC of a resistance R of the region for supplying electrons and a capacitance C of the depletion layer formed in the high density p-type semiconductor region bringing about the avalanche amplification, immediately before the avalanche breakdown occurs, as previously described.
  • the capacitance C of the depletion layer is the same as that of the conventional device, but the distance L which is a factor of the resistance R in the region for supplying electrons is shorter, the product RC is smaller, so that the operating speed increases. Also, as the resistance R is smaller, the heat generation due to the Joule heating is suppressed, thereby contributing to the stabilization of the device in increasing the electron emission amount, particularly by raising the applied voltage.
  • Figs. 10 and 11 the operation principle of the semiconductor electron emission device according to the present invention will be described.
  • applicable semiconductor materials are Si, Ge, GaAs, GaP, AlAs, GaAsP, AlGaAs, SiC, BP, AlN, or diamond in principle, and particularly, the material of indirect transition type and having a wide band gap is preferable.
  • the feature of the present invention is that the distance between the high density p-type semiconductor region 1006 involved in the emission of electrons by bringing about the avalanche amplification as thereinafter described and the high density p-type semiconductor substrate 1001 for supplying electrons to the high density p-type semiconductor region is shorter than the region 1003 of small resistivity.
  • the material for the electrode 1010 requires to form the Schottky junction with the p-type semiconductor, and may be, for example, Al, Au or LaB6, in addition to tungsten (W), as commonly well known.
  • W tungsten
  • the electron emission process in the semiconductor electron emission device of the present invention will be described below. If the reverse bias voltage is applied to the Schottky diode forming the Schottky barrier junction with the p-type semiconductor, the bottom Ec in the conduction band of the p-type semiconductor is at a higher energy level than the vacuum level Evac of the electrode forming the Schottky barrier. Electrons produced with the avalanche amplification obtain the higher energy than at a lattice temperature by the electric field within the depletion layer generated at the semiconductor metal electrode interface, and are injected into the electrode for forming the Schottky barrier junction. The electrons having larger energy than the work function on the electrode surface for forming the Schottky barrier junction are emitted in the vacuum. Accordingly, the treatment of the electrode surface for the lower work function leads to the increase of electron emission amount, as previously described.
  • Figs. 13 and 14 are schematic views showing partially a multielectron emission portion, in which semiconductor electron emission devices in another example of the present invention are arranged like a matrix.
  • Fig. 13 is a plan view thereof, and
  • Fig. 14 is a cross-sectional view taken along the line A-A' of Fig. 13.
  • 1301 is a semiinsulating semiconductor substrate
  • 1302 is a strike-like high density p-type semiconductor region longitudinally in the X direction
  • 1303 is a semi-insulating semiconductor layer
  • 1304 is a high density p-type semiconductor region having a small resistivity which is a feature of the present invention
  • 1305 is a semi-insulating semiconductor layer
  • 1306 is a p-type semiconductor region leading to the high density p-type semiconductor region 1302
  • 1307 is a ring-like n-type semiconductor region
  • 1308 is a high density p-type semiconductor regin bringing about the avalanche amplification
  • 1309 is a high density p-type semiconductor region in contact with the high density p-type semiconductor region 1302
  • 1310 is an insulator layer
  • 1311 is an electrode which is an ohmic junction to the n-type semiconductor region 1307, shaped like a ring and disposed lengthwise in the Y direction
  • 1312 is an ohmic junction
  • the multi semiconductor electron emission device having the electron emission portions thus fabricated arranged like a matrix, 20 in the X direction, and 15 in the Y direction, was installed within a vacuum chamber which was evacuated to a vacuum of about 1x10 ⁇ 7Torr. If a reverse bias voltage of 7V was applied to the entire area of the multi device, the electron emission of about 60nA in total was observed. The operating speed of this device was substantially the same as that of single device. In the driving for a long time, there was no breakage or deterioration of the device or no fluctuation in the electron emission amount.
  • the present invention it is possible to make faster the operating speed of the device by providing the semiconductor region of small resistivity or metallic electrode for supplying electrons in direction contact with the high density p-type semiconductor region bringing about the avalanche breakdown. Further, it is possible to avoid the breakage or deterioration of the device due to the Joule heating in the vicinity of the high density p-type semiconductor region bringing about the avalanche amplification, and reduce the fluctuation in the electron emission amount.
  • Fig. 15 shows schematically a semiconductor electron emission device in one example of the present invention, in which Fig. 15A is a plan view thereof, and Fig. 15B is a cross-sectional view taken along the line A-A' of Fig. 15A.
  • 1501 is a high density p-type semiconductor substrate
  • 1502 is a p-type semiconductor layer
  • 1503 is a high density p-type semiconductor region
  • 1504 is a p-type semiconductor layer
  • 1505 is a ring-like n-type semiconductor region
  • 1506 is a high density p-type semiconductor region bringing about the avalanche amplification
  • 1507 is an insulating film
  • 1508, 1509 are ohmic junction electrodes, respectively
  • 1510 is a metallic electrode which is a Schottky barrier junction
  • 1511 is an end of a depletion layer when a reverse voltage calculated is applied
  • 1512 is a power source.
  • the semiconductor electron emission device (Fig. 15) thus fabricated was installed within a vacuum chamber which was retained at a vacuum of about 1x10 ⁇ 7Torr, and when a reverse bias voltage of 5V was applied from the power source 1511, the electron emission of about 0.lnA was observed from the W surface above the high density p-type semiconductor region 1506, and when the applied voltage was further increased up to 10V, the electron emission of about lnA was observed.
  • the breakage or unstable emission current during the electron emission which occurred with a conventional device, was not observed.
  • the semiconductor electron emission device realized the fast driving so that the operating speed from the application of electrons to their emission was about 1/4 or less that of the conventional device not having the high density p-type semiconductor region 1503 of the present invention, when the structure and the size were the same. This is because the factor of determining the operating speed of the device depends on the product RC of a resistance R of the region for supplying electrons and a capacitance C of the depletion layer formed in the high density p-type semiconductor region bringing about the avalanche amplification, immediately before the avalanche breakdown occurs, as previously described.
  • the capacitance C of the depletion layer is the same as that of the conventional device, but the resistance R in the region for supplying electrons is shorter, the product RC is smaller, so that the operating speed increases. Also, as the resistance R is smaller, the heat generation due to the Joule heating is suppressed, thereby contributing to the stabilization of the device in increasing the electron emission amount, particularly by raising the applied voltage.
  • Figs. 12 and 15 the operation principle of the semiconductor electron emission device according to the present invention will be described.
  • applicable semiconductor materials are Si, Ge, GaAs, GaP, AlAs, GaAsP, AlGaAs, SiC, BP, AlN, or diamond in principle, and particularly, the material of indirect transition type and having a wide band gap is preferable.
  • the feature of the present invention is that the resistance between the high density p-type semiconductor region 1506 involved in the emission of electrons by bringing about the avalanche amplification as thereinafter described and the high density p-type semiconductor substrate 1501 for supplying electrons to the high density p-type semiconductor region is smaller.
  • the material for the electrode 1510 requires to form the Schottky barrier junction with the p-type semiconductor, and may be, for example, Al, Au or LaB6, in addition to tungsten (W), as commonly well known.
  • the electron emission efficiency increases with smaller work function of the electrode surface, the electron emission efficiency can be increased by coating a material of low work function such as Cs on the surface, when the work function of the material is large.
  • the electron emission process in the semiconductor electron emission device using the Schottky barrier junction of the present invention will be described below. If the reverse bias voltage is applied to the Schottky diode forming the Schottky barrier junction with the p-type semiconductor, the bottom Ec in the conduction band of the p-type semiconductor is at a higher energy level than the vacuum level Evac of the electrode forming the Schottky barrier. Electrons produced with the avalanche amplification obtain the higher energy than at a lattice temperature by the electric field within the depletion layer generated at the semiconductor-metal electrode interface, and are injected into the electrode for forming the Schottky barrier junction. The electrons having large energy than the work function on the electrode surface for forming the Schottky barrier junction are emitted in the vacuum. Accordingly, the treatment of the electrode surface for the lower work function leads to the increase of electron emission amount, as previously described.
  • Fig. 16 shows schematically a semiconductor electron emission device using the pn junction in one example of the present invention, in which Fig. 16A is a plan view thereof, and Fig. 16B is a cross-sectional view taken along the line A-A' of Fig. 16A.
  • 1601 is a high density p-type semiconductor substrate
  • 1602 is a p-type semiconductor layer
  • 1603 is a high density p-type semiconductor region
  • 1604 is a p-type semiconductor layer
  • 1605 is a ring-like n-type semiconductor region
  • 1606 is a high density p-type semiconductor region bringing about the avalanche amplification
  • 1607 is a high density n-type semiconductor layer forming the pn junction with the p-type semiconductor 1604 and the high density p-type semiconductor region 1606,
  • 1608 is an insulating film
  • 1609, 1610 are ohmic junction electrodes, respectively
  • 1611 is a thin film of low work function material
  • 1612 is an end of a depletion layer when a reverse bias voltage calculated is applied
  • 1613 is a power source.
  • the semiconductor electron emission device of pn junction type thus fabticated was installed within a vacuum chamber which was retained at a vacuum of about 1x10 ⁇ 9Torr or less, and when a reverse bias voltage of 7V was applied from the power source 1611, the electron emission of about lnA was observed. However, the breakage or unstable emission current during the electron emission, which occurred with a conventional device, was not observed. Also, the semiconductor electron emission device realized the fast driving so that the operating speed from the application of electrons to their emission was about 1/4 or less that of the conventional device not having the high density p-type semiconductor region 1603 of the present invention, when the structure and the size were the same.
  • Fig. 17 shows schematically a multi electron emission portion; in part, in which semiconductor electron emission devices in another example of the present invention are arranged like a matrix.
  • Fig. 17A is a plan view thereof, and Fig. 17B is a cross sectional view taken along the line A-A' of Fig. 17A.
  • 1701 is a semi-insulating semiconductor substrate
  • 1702 is a stripe-like high density p-type semiconductor region, disposed lengthwise in the X direction
  • 1703 is a semi-insulating semiconductor layer
  • 1704 is a high density p-type semiconductor region
  • 1705 is a semi-insulating semiconductor layer
  • 1706 is a p-type semiconductor region leading to the high density p-type semiconductor region 1702
  • 1707 is a ring-like n-type semiconductor region
  • 1708 is a high density p-type semiconductor region bringing about the avalanche amplification
  • 1709 is a high density p-type semiconductor region in contact with the high density p-type semiconductor region 1702
  • 1710 is an insulator layer
  • 1711 is an electrode which is an ohmic junction to the n-type semiconductor region 1707, shaped like a ring and disposed lengthwise in the Y direction
  • 1712 is an ohmic junction electrode to the high density p-type semiconductor region
  • the multi semiconductor electron emission device having the electron emission portions thus fabricated arranged like a matrix, 20 in the X direction, and 15 in the Y direction, was installed within a vacuum chamber which was evacuated to a vacuum of about 1x10 ⁇ 7Torr. If a reverse bias voltage of 7V was applied to the entire area of the multi device, the electron emission of about 60nA in total was observed. The operating speed of this device was substantially the same as that of single device. In the driving for a long time, there was no breakage or deterioration of the device or no fluctuation in the electron emission amount.
  • the present invention can exhibit the following effects owing to the constitution as above described.
  • a high density p-type semiconductor region and a p-type semiconductor region 104 for supplying carriers to the high density p-type semiconductor region are disposed in contact, further, a p-type semiconductor region and a low density p-type semiconductor region are disposed outwardly around the high density p-type semiconductor region and the p-type semiconductor region, and on a surface of device, a Schottky electrode which is a metallic film for forming the Schottky barrier junction with the high density p-type semiconductor region is disposed.
  • the density relation between carrier densities of the semiconductor regions is such that high density p-type semiconductor region > p-type semiconductor region > p-type semiconductor region > low density p-type semiconductor region.

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EP92102746A 1991-02-20 1992-02-19 Dispositif semiconducteur émetteur d'électrons Expired - Lifetime EP0504603B1 (fr)

Applications Claiming Priority (8)

Application Number Priority Date Filing Date Title
JP45579/91 1991-02-20
JP4557991A JP3135070B2 (ja) 1991-02-20 1991-02-20 半導体電子放出素子
JP55597/91 1991-02-28
JP5559791A JP3137267B2 (ja) 1991-02-28 1991-02-28 半導体電子放出素子
JP23445791A JPH0574331A (ja) 1991-09-13 1991-09-13 半導体電子放出素子
JP234456/91 1991-09-13
JP234457/91 1991-09-13
JP23445691A JPH0574330A (ja) 1991-09-13 1991-09-13 半導体電子放出素子

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Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7399987B1 (en) 1998-06-11 2008-07-15 Petr Viscor Planar electron emitter (PEE)

Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4303930A (en) * 1979-07-13 1981-12-01 U.S. Philips Corporation Semiconductor device for generating an electron beam and method of manufacturing same
US4801994A (en) * 1986-03-17 1989-01-31 U.S. Philips Corporation Semiconductor electron-current generating device having improved cathode efficiency
EP0331373A2 (fr) * 1988-02-27 1989-09-06 Canon Kabushiki Kaisha Dispositif semi-conducteur émetteur d'électrons

Patent Citations (3)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US4303930A (en) * 1979-07-13 1981-12-01 U.S. Philips Corporation Semiconductor device for generating an electron beam and method of manufacturing same
US4801994A (en) * 1986-03-17 1989-01-31 U.S. Philips Corporation Semiconductor electron-current generating device having improved cathode efficiency
EP0331373A2 (fr) * 1988-02-27 1989-09-06 Canon Kabushiki Kaisha Dispositif semi-conducteur émetteur d'électrons

Cited By (1)

* Cited by examiner, † Cited by third party
Publication number Priority date Publication date Assignee Title
US7399987B1 (en) 1998-06-11 2008-07-15 Petr Viscor Planar electron emitter (PEE)

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