JP4787083B2 - Semiconductor light emitting device - Google Patents

Description

  The present invention relates to a semiconductor light emitting device.

  Examples of conventional semiconductor light emitting devices include light emitting diodes and laser diodes. In these semiconductor light emitting devices, a pair of electrodes are provided with a p-type semiconductor layer and an n-type semiconductor layer bonded to each other, and when a forward bias voltage is applied between the pair of electrodes, An active region is formed in the vicinity of the pn junction between the semiconductor layer and the n-type semiconductor layer, and light is generated in this active region by annihilation (recombination) of electrons and holes.

In addition, for use in quantum information processing and quantum information communication that is significantly faster than conventional methods, quantum entanglement (a method of generating photon pairs by parametric down-conversion of laser light, etc.) Techniques for generating photon pairs have not been developed (see Non-Patent Document 1).
PG Kwiat, K. Mattle, H. Weinfurter, A. Zeilinger, AVSergienko, and Y. Shih: "New high-intensity source ofpolarization-entangled photon pairs," Physical Review Letters, Vol. 75, No. 24 (1995) pp .4337-4341.

  However, in the method of down-converting laser light parametrically, (a) the timing of generating photon pairs cannot be controlled, and (b) only one photon pair cannot be generated at a certain time. There were problems that a plurality of photon pairs were generated, and (c) the speed of generating photon pairs was slow. The present invention has been made to solve the above problems, and an object of the present invention is to provide a semiconductor light emitting element suitable for use in quantum information processing and quantum information communication.

A semiconductor light emitting device according to the present invention is provided on a first conductive type semiconductor substrate, a first conductive type first semiconductor layer provided on one main surface of the semiconductor substrate, and a first semiconductor layer. A second conductive type second semiconductor layer; a superconducting first electrode provided on the second semiconductor layer; a second electrode provided on the other main surface of the semiconductor substrate; And a semiconductor quantum dot region provided between the second semiconductor layer. Furthermore, the semiconductor light emitting device according to the present invention is injected from the first electrode in the semiconductor quantum dot region by injecting a pulse current having a width shorter than the recombination time between the first electrode and the second electrode. The electron cooper pair and the two holes injected from the first semiconductor layer are simultaneously recombined, or the hole cooper pair injected from the first electrode and the two holes injected from the first semiconductor layer It is characterized by recombining electrons simultaneously. Here, one of the first conductivity type and the second conductivity type is p-type, and the other is n-type. In addition, each of the semiconductor substrate, the first semiconductor layer, the second semiconductor layer, and the semiconductor quantum dot region is preferably made of a compound semiconductor.

  In this semiconductor light emitting device, a first conductive type first semiconductor layer, a second conductive type second semiconductor layer, and a superconductive first electrode are sequentially formed on one main surface of a first conductive type semiconductor substrate. Is provided. A second electrode is provided on the other main surface of the first conductivity type semiconductor substrate. A semiconductor quantum dot region is provided between the first semiconductor layer and the second semiconductor layer. In the semiconductor light emitting device having such a configuration, when a forward bias voltage is applied between the first electrode and the second electrode, the pn junction between the first semiconductor layer and the second semiconductor layer has superconductivity. An electron cooper pair is injected from the first electrode of the first electrode and holes are injected from the first semiconductor layer, and the electron cooper pair and the hole are recombined simultaneously to generate two photons that cannot be distinguished from each other at the same time. The Alternatively, a hole cooper pair is injected from the superconducting first electrode and electrons are injected from the first semiconductor layer into the pn junction between the first semiconductor layer and the second semiconductor layer. The pair and electron recombine simultaneously, producing two simultaneously indistinguishable photons.

  The semiconductor light emitting device according to the present invention can generate quantum entangled (indistinguishable) photon pairs and is preferably used in quantum information processing and quantum information communication.

  The best mode for carrying out the present invention will be described below in detail with reference to the accompanying drawings. In the description of the drawings, the same elements are denoted by the same reference numerals, and redundant description is omitted.

  FIG. 1 is a cross-sectional view of a semiconductor light emitting device 1 according to this embodiment. As shown in this figure, the semiconductor light emitting device 1 according to this embodiment includes a first conductive type semiconductor substrate 11 and a first conductive type first semiconductor provided on one main surface of the semiconductor substrate 11. Layer 12, second conductive type second semiconductor layer 14 provided on first semiconductor layer 12, superconducting first electrode 15 provided on second semiconductor layer 14, and the other of semiconductor substrate 11 And a second electrode 16 provided on the main surface. Further, the semiconductor light emitting device 1 includes a semiconductor quantum dot region 13 provided between the first semiconductor layer 12 and the second semiconductor layer 14. Here, one of the first conductivity type and the second conductivity type is p-type, and the other is n-type. Further, each of the semiconductor substrate 11, the first semiconductor layer 12, the second semiconductor layer 14, and the semiconductor quantum dot region 13 is preferably made of a compound semiconductor.

  For example, the semiconductor substrate 11 is made of p-type GaAs, the first semiconductor layer 12 is made of p-type AlGaAs, the semiconductor quantum dot region 13 is made of GaSb, and the second semiconductor layer 14 is made of n-type GaAs. As a method for manufacturing the semiconductor light emitting device 1 having such a configuration, for example, a wide range of techniques such as MOCVD, MBE, and MOMBE are appropriately employed.

  In such a semiconductor light emitting device 1, when a forward bias voltage is applied between the superconducting first electrode 15 and the second electrode 16, holes are transferred from the p-type AlGaAs semiconductor layer 12 to the GaSb semiconductor quantum dot region 13. Are injected into the GaSb semiconductor quantum dot region 13 from the superconducting electrode 15 through the n-type GaAs semiconductor layer 14, and the electron Cooper pair and two holes are recombined simultaneously. Thus, two indistinguishable photons are generated simultaneously.

  The number of holes injected into one quantum level in the semiconductor quantum dot region 13 is limited to two due to Pauli's exclusion rule for Fermi particles. On the other hand, there is no limit on the number of Cooper pairs that are Bose particles. Therefore, the number of generated photons is determined by the number of holes injected into the quantum level of the semiconductor quantum dot region 13 and is two. The two holes injected into the quantum level of the semiconductor quantum dot region 13 have the same energy and are indistinguishable. The electron cooper pair is a state in which two electrons are combined and is indistinguishable from each other, and therefore recombines simultaneously with two holes. This recombination generates two indistinguishable photons simultaneously.

  There are a plurality of quantum levels in the semiconductor quantum dot region 13, but if a pulse current having a width shorter than the recombination time is injected between the electrodes 15 and 16, the holes disappear from the upper level holes, Using the ground level hole pair that recombines last, only one photon pair can be generated at a time. The generated photons are taken out from the openings provided in the electrodes 15 and 16 respectively. The generation rate of the photon pair is determined by the repetition time of the pulse current, and can be repeated in a short time such as the recombination time.

  In this case, the thickness of the n-type GaAs semiconductor layer 14 is determined by the transport efficiency for injecting the Cooper pair into the GaSb semiconductor quantum dot region 13 and is about 100 nm from the measurement result. The Al composition of the p-type AlGaAs semiconductor layer 12 is determined from preventing the electron cooper pair from entering this layer, and needs to be about 15%. The openings provided in each of the electrode 15 and the electrode 16 are determined based on conditions for extracting light emitted from a single quantum dot. When the surface density of the quantum dots is about 1 in 1 μm square, a diameter of about 1 μm is required. . The recombination time is usually about 1 ns, and the repetition of the pulse current and the accompanying photon pair generation rate can be up to about 1 GHz.

  Alternatively, the semiconductor substrate 11 is made of p-type GaAs, the first semiconductor layer 12 is made of p-type AlGaAs, the semiconductor quantum dot region 13 is made of ZnTe, and the second semiconductor layer 14 is made of n-type ZnSe. Good. In this case, when a forward bias voltage is applied between the superconducting first electrode 15 and the second electrode 16, holes are injected from the p-type AlGaAs semiconductor layer 12 into the ZnTe semiconductor quantum dot region 13. At the same time, an electron Cooper pair is injected from the superconducting electrode 15 into the ZnTe semiconductor quantum dot region 13 through the n-type ZnSe semiconductor layer 14, and the electron Cooper pair and two holes are simultaneously recombined. Two indistinguishable photons are generated simultaneously.

  In the embodiment described so far, the semiconductor substrate 11 is made of a p-type semiconductor, but the semiconductor substrate 11 may be made of an n-type semiconductor. In the latter case, for example, the semiconductor substrate 11 is made of n-type GaAs, the first semiconductor layer 12 is made of n-type AlGaAs, the semiconductor quantum dot region 13 is made of InP, and the second semiconductor layer 14 is made of p-type GaAs. In this case, when a forward bias voltage is applied between the superconducting first electrode 15 and the second electrode 16, the hole cooper pair is transferred from the superconducting electrode 15 through the p-type GaAs semiconductor layer 14 to InP. While being injected into the semiconductor quantum dot region 13, electrons are injected from the n-type AlGaAs semiconductor layer 12 into the InP semiconductor quantum dot region 13, and these hole cooper pairs and two electrons are simultaneously recombined to form 2 Two indistinguishable photons are generated simultaneously.

  In addition, the semiconductor substrate 11, the first semiconductor layer 12, the semiconductor quantum dot region 13, and the second semiconductor layer 14 may have various modes.

  As described above, the semiconductor light emitting device according to the present embodiment is based on a semiconductor pn junction, uses a superconductor for one electrode, and injects a Cooper pair from the superconductor electrode into the semiconductor. Using quantum levels of semiconductor quantum dots, also called artificial atoms, two electrons or two holes are distributed in each quantum level of the conduction band or valence band, and only one pair of entanglements at a time Photon pairs can be generated. Therefore, this semiconductor light emitting device can be suitably used in quantum information processing with high processing speed and quantum information communication with high safety.

It is sectional drawing of the semiconductor light-emitting device 1 which concerns on this embodiment.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... Semiconductor light-emitting device, 11 ... 1st conductivity type semiconductor substrate, 12 ... 1st conductivity type 1st semiconductor layer, 13 ... Semiconductor quantum dot area | region, 14 ... 2nd conductivity type 2nd semiconductor layer, 15 ... Super Conductive first electrode, 16 ... second electrode.

Claims (1)

A first conductivity type semiconductor substrate;
A first semiconductor layer of a first conductivity type provided on one main surface of the semiconductor substrate;
A second semiconductor layer of a second conductivity type provided on the first semiconductor layer;
A superconducting first electrode provided on the second semiconductor layer;
A second electrode provided on the other main surface of the semiconductor substrate;
A semiconductor quantum dot region provided between the first semiconductor layer and the second semiconductor layer;
Bei to give a,
A pulse current having a width shorter than the recombination time is injected between the first electrode and the second electrode, and in the semiconductor quantum dot region, the electron cooper pair injected from the first electrode and the first electrode Two holes injected from the semiconductor layer are simultaneously recombined, or a hole cooper pair injected from the first electrode and two electrons injected from the first semiconductor layer are simultaneously combined. Recombine,
A semiconductor light emitting element characterized by the above.

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