JP4637517B2 - Light emitting device and image recording device - Google Patents

Abstract

<P>PROBLEM TO BE SOLVED: To provide a light emitting apparatus with excellent reliability whose whole structure can be simplified. <P>SOLUTION: A light emitting apparatus with high photosensitivity comprises a three terminal light emitting switch device array 16 according to optical excitation wherein many three terminal light emitting switch devices are linearly arranged and a three terminal light emitting device array 15, wherein many three terminal light emitting devices are arranged corresponding to the three terminal light emitting switch devices. Because a light emitter is formed on a light receiving part in the three terminal light emitting switch device so that the light emitter is formed with deviation toward the side opposite to the incident side of the light emitted from the adjacent three terminal light emitting device, in addition to the side surface of the light receiver of the three terminal light emitting switch device, the region on the light receiver can also receive the light wherein the light emitting part is not disposed. Therefore, the light receiving area is increased, and the light emitting apparatus with high photosensitivity can be obtained. <P>COPYRIGHT: (C)2006,JPO&amp;NCIPI

Description

  The present invention relates to a light-emitting device using a light-emitting thyristor and integrating transfer switch elements by optical excitation, and more particularly to a light-emitting device that can simplify the overall structure and has high reliability. The present invention also relates to an image recording apparatus using a light emitting device in which transfer switch elements by such light excitation are integrated.

  A light-emitting thyristor, which is a negative resistance element having a PNPN structure, is used as a light-emitting device as a light-emitting device used as an optical printer head, which is one of the exposure devices of electrophotographic printers among image recording devices. Proposals have been made for light emitting devices that can be arranged as element rows and realize light emission state transfer. By using this for an optical printer head, it is easy to mount and a light emitting element array can be made compact. (For example, refer to Patent Documents 1 and 2).

  FIG. 8 is a cross-sectional view showing the basic structure of a conventional light-emitting thyristor together with a diagram showing the carrier density state of each layer. In FIG. 8, reference numeral 21 denotes an n-type semiconductor substrate such as GaAs, and various semiconductor layers 22 to 26 made of GaAs or AlGaAs are stacked on the n-type semiconductor substrate 21. In general, 22 is an n-type AlGaAs layer, 23 is a p-type AlGaAs layer, 24 is an n-type AlGaAs layer, 25 is a p-type AlGaAs layer, and 26 is for easy ohmic contact with the anode terminal 27. P-type GaAs layer. Reference numeral 27 denotes an anode terminal, 28 denotes a gate terminal, and 29 denotes a cathode terminal on the back surface of the n-type semiconductor substrate 21.

  FIG. 9 shows the current-voltage characteristics of such a light emitting thyristor. FIG. 9 is a diagram schematically showing forward voltage-current characteristics between the anode terminal 27 and the cathode terminal 29 of the light-emitting thyristor, in which the horizontal axis represents the anode voltage, the vertical axis represents the anode current, and the solid line. The broken characteristic curve indicates the relationship between the anode voltage and the anode current. As shown by a solid characteristic curve in the figure, this light-emitting thyristor has an S-shaped negative resistance similar to that of a normal thyristor. This current-voltage characteristic is determined by the voltage or current applied to the gate terminal 28 or by irradiating the semiconductor layer with light, as shown by the dashed characteristic curve in FIG. It is known that the voltage or threshold current can be changed (reduced), whereby the light emitting thyristor functions as a switch. The change due to the light irradiation is such that the NPN layer portion of the n-type AlGaAs layer 22, the p-type AlGaAs layer 23, and the n-type AlGaAs layer 24 functions as a phototransistor as a light receiving element, and receives light irradiated from the outside at this portion. This is because the threshold voltage or threshold current of light emission of the light emitting thyristor changes (decreases). When the light-emitting thyristor is in the ON state, light is emitted by a forward current flowing through the PN junctions of the n-type AlGaAs layer 24 and the p-type AlGaAs layer 25 inside the stacked semiconductor layers 22 to 26. By emitting this light to the outside and making this light incident on another light emitting thyristor in the vicinity, it can be operated as a switching array having a self-scanning function capable of sequentially transferring the light emitting state (for example, Patent Documents) 1).

FIG. 10 is an equivalent circuit diagram showing a schematic circuit configuration of a basic structure of a conventional first light emitting device having a self-scanning function using a conventional light emitting thyristor, and a diagram showing waveforms of each clock pulse and light emission intensity. Show. The light emitting thyristors T0 to Tn are arranged in a substantially linear shape, and are configured such that the emitted light sequentially enters the adjacent light emitting thyristors. Since each of the light emitting thyristors T0 to Tn has a characteristic that a threshold voltage or a threshold current is reduced by receiving light irradiation, the threshold voltage of the light emitting thyristor adjacent to the light emitting thyristor is decreased. Become. Further, three clock lines φ1, φ2, and φ3 are repeatedly connected to the anode terminal of each light emitting thyristor every three light emitting thyristors, and current sources I ₁ are connected to the clock lines φ1, φ2, and φ3, respectively. , I ₂ , and I ₃ are connected, and the amount of current is controlled by the light emission signal φI (see, for example, Patent Document 2 and Patent Document 3).

  The operation of the conventional first light emitting device shown in FIG. 10 will be described. First, the start pulse line φS changes from the low level to the high level, whereby the first light emitting thyristor T0 changes from the off state to the on state and emits light. The light emitted from the light emitting thyristor T0 enters the adjacent light emitting thyristor T1, and the threshold voltage of the light emission is lowered by light excitation. At this time, since the light-emitting thyristor T2 and the subsequent light-emitting thyristors T0 are further away from the light-emitting thyristor T0, the incident light is weaker and the threshold voltage for light emission is less lowered. Next, when the clock line φ1 changes from the low level to the high level in this state, the light emission threshold voltage of the light emitting thyristor T1 is reduced by the light irradiation from the light emitting thyristor T0. By setting the level according to the threshold voltage, the light emitting thyristor T1 changes from the off state to the on state and emits light. At this time, since the light emitting thyristor T4 to which the same clock line φ1 is connected is sufficiently away from the light emitting thyristor T0, there is almost no decrease in the threshold voltage of the light emission, so that the clock line φ1 at a level for causing the light emitting thyristor T1 to emit light. No light is emitted at the high level, and only the light emitting thyristor T1 is turned on to emit light. Next, by setting the start pulse φS to a low level, the light-emitting thyristor T0 changes from the on state to the off state, and light emission ends. As a result, the ON state is transferred from T0 to T1.

  Similarly, by changing the waveform of each clock pulse φ1 to φ3 as shown in the diagram of FIG. 10, the light emitting thyristor T1 is then changed to the light emitting thyristor T2, and then the light emitting thyristor T2 is changed to the light emitting thyristor T3. The on state (light emission state) is transferred with time.

For example, when only the clock line φ3 is at a high level and the light-emitting thyristor T3 is in the on state, the light emission from the light-emitting thyristor T3 is most strongly incident on the adjacent light-emitting thyristors T2 and T4, and the threshold voltage of these light emission is set. Reduce. At this time, since the light-emitting thyristors T1 and T5 are located farther from the light-emitting thyristor T3 than the light-emitting thyristors T2 and T4, the light incident from the light-emitting thyristor T3 is weak, and the threshold voltage of the light emission does not decrease so much. In this state, when the clock line φ1 changes from the low level to the high level, the threshold voltage V _TH (T4) of the light emitting thyristor T4 is lower than the threshold voltage V _TH (T1) of the light emitting thyristor T1. , a high-level voltage _{V H} of the clock pulse φ1 only _{V TH (T4) <V H} <V TH (T1) and the light-emitting thyristor by setting T4 emits light in the oN state, the light-emitting thyristor T1 is in an off state Will remain. Then, when the clock line φ3 is changed from the high level to the low level, the light emitting thyristor T3 is turned off, and the on state (light emitting state) is transferred from the light emitting thyristor T3 to the light emitting thyristor T4.

  In this way, by setting the high levels of the clock pulses on the clock lines φ1, φ2, and φ3 so as to partially overlap each other, the on states (light emitting states) of the light emitting thyristors T0 to Tn are sequentially transferred.

  Further, as shown in the diagram of FIG. 10, when only the light emitting thyristor T3 emits light strongly, the light emission signal φI is set to the high level in accordance with the timing at which the light emitting thyristor T3 emits light. As a result, the amount of current applied only to the light-emitting thyristor T3 that is the light-emitting element at that time is increased, and the light emission intensity (L (T3)) is also increased.

  The conventional first light-emitting device uses light emitted from the light-emitting thyristor T3 as light for irradiating the outside.

  However, in the first light emitting device of the related art, as can be seen from the light emission intensities L (T0) to L (T5) shown in FIG. Even when light to be emitted is not emitted, a certain amount of light emission (bias light) is generated from each light emitting thyristor in an on state (light emission state) for transferring a switching signal. This is because weak light emission is generated from each light-emitting thyristor due to the current for maintaining the on-state. However, when this conventional first light-emitting device is applied to an optical printer head or the like of an image recording apparatus, this bias light is used. However, since the photosensitive member is irradiated with light and acts as noise with respect to the irradiation light for original image recording, there is a problem that the image quality is deteriorated.

  Therefore, in order to solve such problems, a structure in which elements for transferring a switching signal are separated and these elements are electrically controlled has been proposed (for example, Patent Documents 4 and 4) See 5).

FIG. 11 is an equivalent circuit diagram showing a schematic circuit configuration of a basic structure of a conventional second light emitting device having such a self-scanning function. The light-emitting thyristor array in the conventional second light-emitting device has a portion in which switch thyristors (T1 to Tn) for switching signals are arranged substantially linearly, and a light-emitting device for emitting light to be irradiated to the outside. The light emitting thyristors (L1 to Ln) have portions arranged in a substantially straight line. The corresponding gate terminals of the switch thyristor and the light emitting thyristor are electrically connected to each other (for example, the gate terminals of the nth switch thyristor Tn and the nth light emitting thyristor Ln are connected to each other). The gate terminal of the first switch thyristor T1 is connected to the start pulse line φS. The gate terminals of the switch thyristors T1 to Tn are connected to the control power supply V _GK via the load resistor _RL, and the clock terminals φ1 and φ2 are connected to every other one of the anode terminals. The

  The gate terminal of the first switch thyristor T1 is electrically connected to the gate terminal of the second switch thyristor T2 via the transfer direction designating diode D. Thereafter, each gate terminal is repeatedly connected in the same manner. Are electrically connected.

  A description will be given of the light emission state transfer and light emission using a switch element by conventional electrical control in such a conventional second light emitting device.

  The light emission state transfer starts when the start pulse line φS changes from the high level to the low level. As a result, the threshold voltage for light emission of the first switch thyristor T1 is lowered. At this time, the clock line φ2 is changed from the low level to the high level, so that the first switch thyristor T1 is turned on to emit light. After the second switch thyristor T2, the transfer direction designating diode D causes the switch thyristors T2, T3,... To move away from the first switch thyristor T1, depending on the forward voltage drop of the transfer direction designating diode D. The voltage applied to the gate terminal rises. Therefore, in the third switch thyristor T3 to which the same clock line φ2 is connected, the light emission threshold voltage is increased by the forward voltage drop corresponding to the two transfer direction designating diodes D, so that the clock pulse φ2 By using a start pulse whose high level is equal to or lower than the threshold voltage for light emission of the third switch thyristor T3, only the first switch thyristor T1 is turned on to emit light.

  In this state, when the power supply line φI for the light emitting thyristors L1 to Ln is changed from the low level to the high level, in the first light emitting thyristor L1, the light emission on condition is the first in which the gate terminals are electrically connected to each other. Therefore, the first light emitting thyristor L1 is turned on and emits light, and the first light emitting unit emits light and is lit. Next, by returning the power supply line φI to the low level, the first light-emitting thyristor L1 is turned off and light emission ends.

  Next, the light emission state transfer (transfer of the ON condition) from the first switch thyristor T1 to the second switch thyristor T2 will be described. Even when the first light-emitting thyristor L1 is turned off, the clock line φ2 remains at the high level, so the first switch thyristor T1 is kept in the on-state (light-emitting state). At this time, the voltage applied to the gate terminal of the second switch thyristor T2 is higher than the first switch thyristor T1 by the forward voltage drop of one transfer direction designation diode D, and the same clock line φ1 is connected. In the fourth switching thyristor T4, the voltage applied to the gate terminal is further increased by the forward voltage drop of two transfer direction designating diodes D. When the clock line φ1 is changed from the low level to the high level in this state, the voltage is between the light emission threshold voltage of the second switch thyristor T2 and the light emission threshold voltage of the fourth switch thyristor T4. Thus, if the high level of the clock pulse φ1 is selected, only the second switch thyristor T2 is turned on to emit light.

After the second switch thyristor T2 is turned on (light emission state) in this way, the first switch thyristor T1 becomes the first light emission thyristor L1 by changing the clock line φ2 from the high level to the low level. In the same manner as when the light is turned off, the light is turned off and light emission ends. At this time, since the start pulse line φS changes from the low level to the high level, the voltage applied to the gate terminal of the first switch thyristor T1 by the transfer direction designation diode D is substantially equal to the voltage of the control power supply V _GK. Thus, the switch thyristor having the lowest emission threshold voltage is the second switch thyristor T2. Thus, the ON state (light emission state) of the switch thyristor is transferred from the first switch thyristor T1 to the second switch thyristor T2. At this time, when the power supply line φI is changed from the low level to the high level, only the second light emitting thyristor L2 is turned on to emit light.

By sequentially repeating the above operations, the light emission states of the switch thyristors T0 to Tn are sequentially transferred, and the light emission states of the light emission thyristors L1 to Ln can be controlled accordingly.
JP-A-49-124992 Japanese Patent No. 2757334 Japanese Patent No. 3020177 Japanese Patent No. 2577089 JP 2003-243696 A

  However, in the above-described conventional first light emitting device, since the light emitting thyristor receives light emitted and the adjacent light emitting thyristor is photoexcited, the light extraction efficiency to the outside of the light emitting thyristor is high. In addition, the light receiving thyristor that receives light is required to have high light receiving sensitivity. In addition, as described above, there is a problem that image quality deteriorates when applied to an optical printer head or the like due to generation of bias light for transferring a switching signal.

Further, in the above-described conventional second light emitting device, since the switching signal is transferred in the switch thyristor and the threshold voltage of light emission of the light emitting thyristor by the switch thyristor is not used, the light excitation of the light emitting thyristor is not used. It is not important that the efficiency of extracting light to the outside of the light emitting thyristor that emits light or the light receiving sensitivity of the light emitting thyristor that receives light is high. However, since the transfer is realized by the electrical control of the thyristor in the element array for transferring the switching signal, the voltage applied to the transfer direction specifying diode D for specifying the transfer direction and the gate terminal of the switching thyristor is controlled. Load resistance R _{L and the} like are required. Therefore, the configuration of the switch thyristor becomes complicated, and there is a problem that the number of processes is increased in manufacturing.

  The present invention has been made in view of the problems in the prior art as described above, and an object of the present invention is to provide a transfer switch by optical excitation that can simplify the overall structure and has excellent reliability. An object of the present invention is to provide a light emitting device having a structure in which elements are integrated. Still another object of the present invention is to provide an image recording apparatus using the light emitting device of the present invention to obtain a recorded image with good image quality.

  The light-emitting device of the present invention includes a large number of three-terminal light-emitting switch elements having an anode terminal, a cathode terminal, and a gate terminal, which can control a light emission threshold voltage or threshold current by irradiating light from the outside. Three terminals that are arranged in a straight line so that light emitted from the three terminal light emitting switch elements is incident on the adjacent three terminal switch elements, and a clock line is connected to the anode terminal of each of the three terminal light emitting switch elements A number of three-terminal light-emitting elements having an anode terminal, a cathode terminal, and the gate terminal, the light-emitting switch element array, and a threshold voltage or threshold current of light emission that can be electrically controlled from the outside via the gate terminal; The gate terminals of the three-terminal light emitting elements correspond to the three-terminal light emitting switch elements, respectively. A three-terminal light-emitting element array electrically connected to the gate terminal of the three-terminal light-emitting switch element, and the anode terminal of the three-terminal light-emitting element connected to a line for supplying voltage or current for light emission. The three-terminal light-emitting switch element and the three-terminal light-emitting element are respectively formed on a n-type semiconductor substrate, a first n-type semiconductor layer, a first p-type semiconductor layer, and a second n-type semiconductor layer. Are sequentially stacked, and a light emitting portion in which a third n-type semiconductor layer and a second p-type semiconductor layer are stacked on the light-receiving portion, and the second p-type semiconductor layer includes A light-emitting thyristor in which the anode terminal is electrically connected to the n-type semiconductor substrate or the first n-type semiconductor layer, and the gate terminal is electrically connected to the second or third n-type semiconductor layer; Yes, 3 terminals Optical switching element, wherein the light emitting portion on the light-receiving portion, the light emitting from the 3-terminal light emitting switch element adjacent and is characterized in that it is arranged disproportionately on the side opposite to the side where the incident.

  In the light emitting device of the present invention, in the above configuration, a reflective layer that reflects the light emission is provided so as to cover the light emitting unit and the light receiving unit adjacent to each other of the three-terminal light emitting switch elements arranged linearly. It is characterized by being.

  In the above structure, the light-emitting device of the present invention is characterized in that the clock line also serves as the reflective layer.

  In the light emitting device according to the present invention, in the above configuration, the three terminal light emitting switch element array and the three terminal light emitting element array are arranged in parallel on a substrate, and light is emitted from the three terminal light emitting switch element. Among them, a light-shielding layer is provided on the surface of the substrate for shielding light emitted in the vertical direction, light emitted in the direction of the three-terminal light-emitting element, and light emitted in the direction opposite to the three-terminal light-emitting element.

  The image recording apparatus of the present invention is characterized in that the light emitting device of the present invention is used in an exposure device for a photoreceptor.

  According to the light emitting device of the present invention, a large number of three-terminal light emitting switch elements having an anode terminal, a cathode terminal, and a gate terminal, which can control the light emission threshold voltage or threshold current by irradiating light from the outside. A three-terminal light-emitting switch in which light from one three-terminal light-emitting switch element is linearly arranged so as to enter an adjacent three-terminal switch element, and a clock line is connected to each anode terminal of the three-terminal light-emitting switch element Many three-terminal light-emitting elements having an anode terminal, a cathode terminal, and a gate terminal, which can electrically control the threshold voltage or threshold current of light emission from the outside via the gate terminal, and the element array. The gate terminals of the three-terminal light-emitting elements are arranged corresponding to the switch elements, and the gate terminals of the corresponding three-terminal light-emitting switch elements are arranged. And a three-terminal light-emitting element array in which the anode terminal of the three-terminal light-emitting element is connected to a line for supplying voltage or current for light emission. The terminal light emitting element includes a light receiving unit in which a first n type semiconductor layer, a first p type semiconductor layer, and a second n type semiconductor layer are sequentially stacked on an n type semiconductor substrate, and the light receiving unit. A light emitting portion in which a third n-type semiconductor layer and a second p-type semiconductor layer are stacked is provided, and an anode terminal is provided on the second p-type semiconductor layer, and the n-type semiconductor substrate or the first n-type semiconductor layer. A light emitting thyristor in which a cathode terminal is electrically connected to a type semiconductor layer and a gate terminal is electrically connected to a second or third n type semiconductor layer, and the light emitting part is adjacent to the light emitting part From a three-terminal light emitting switch Is biased to the side opposite to the incident side, so that the gate voltage of the three-terminal light-emitting element is controlled by the gate terminal voltage of the three-terminal light-emitting switch element to control the threshold voltage or threshold current of the light emission. The switching signal is transferred by the switch thyristor by light excitation using the light emitting thyristor, so that the voltage applied to the transfer direction specifying diode and the gate terminal in the conventional second light emitting device can be controlled. Therefore, the array structure of the three-terminal light-emitting switch element is simplified, and a transfer direction designation diode is conventionally used in a switching array having a self-scanning function capable of sequentially transferring the light emission state. No need for a Schottky junction fabrication process or load resistance fabrication process Become. In the three-terminal light emitting switch element, the light emitting part is disposed on the light receiving part so as to be biased to the side opposite to the side on which light emitted from the adjacent three terminal light emitting switch element is incident. In addition to the side surface of the light receiving portion of the three-terminal light emitting switch element, the light emitting portion on the light receiving portion is arranged in comparison with the state where light is received only by the side surface of the light receiving portion of the three terminal emitting switch element in the light emitting device of FIG. Since the light can be received even in a region that is not present, the light receiving area is increased, the light receiving sensitivity is increased, and thus a highly reliable light emitting device can be obtained. Furthermore, since the three-terminal light-emitting switch element and the three-terminal light-emitting element are individually provided, there is no problem of bias light due to the combined use of the light-emitting switch element and the light-emitting element as in the conventional first light-emitting device. When the light emitting device of the present invention is used in an electrophotographic image recording apparatus, a recorded image with excellent image quality can be obtained.

  According to the light emitting device of the present invention, in the above configuration, the reflective layer for reflecting the light emission is provided so as to cover the adjacent light emitting portion and light receiving portion of the three-terminal light emitting switch elements arranged in a straight line. When the light is emitted from the light emitting part of one of the three-terminal light-emitting switch elements between the adjacent three-terminal light-emitting switch elements, the other three-terminal light-emitting switch The light can be efficiently guided to the light receiving portion of the element.

  Further, according to the light emitting device of the present invention, in the above configuration, when the clock line also serves as the reflection layer, the light emission from the light emitting portion of one of the three terminal light emitting switch elements is between the adjacent three terminal light emitting switch elements. The light leaking upward in the clock line can be reflected and efficiently guided to the light receiving portion of the other three-terminal light emitting switch element.

  According to the light-emitting device of the present invention, in the above configuration, the three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate, and light emitted from the three-terminal light-emitting switch element is emitted. Of these, when a light-shielding layer is provided on the surface of the substrate to block light emission in the vertical direction, light emission in the direction of the three-terminal light-emitting element, and light emission in the opposite direction of the three-terminal light-emitting element, Light emission in the direction perpendicular to the surface of the substrate, light emission in the direction of the three-terminal light-emitting element, and light emission in the opposite direction of the three-terminal light-emitting element are sufficiently shielded by this light-shielding layer. Therefore, it is possible to efficiently use only the light emitted in the direction of the adjacent three-terminal light-emitting switch element, to suppress the influence of leaking light, and to Only the output light from the Lee outside becomes that can be efficiently extracted.

  Further, according to the image recording apparatus of the present invention, an electrophotographic image recording apparatus, in which the light emitting apparatus of the present invention is used as an exposure apparatus for a photosensitive member, and therefore, in a light emitting apparatus as an exposure apparatus. Since the light emitting element for performing image exposure on the photosensitive member and the switch element for signal transfer can be integrated, a circuit board that mounts the light emitting device and constitutes the exposure apparatus is provided. The size can be reduced, and the number of wire bondings to the circuit board and the number of drive ICs to be mounted on the circuit board can be reduced, so that it is possible to reduce the size and provide a low-cost exposure apparatus. An image recording apparatus can be provided.

  Hereinafter, an example of an embodiment of a light emitting device of the present invention will be described with reference to the drawings.

  FIG. 1A is a cross-sectional view showing an example of the layer structure of a light-emitting thyristor used in the light-emitting device of the present invention, and FIG. 1B is a cross-sectional view showing another example of the layer structure of the light-emitting thyristor.

  In FIG. 1, 1 is an n-type semiconductor substrate made of Si, GaAs or the like, 2 is a first n-type semiconductor layer made of GaAs or the like, 3 is a first p-type semiconductor layer made of InGaAs or the like, 4a is made of GaAs or the like. A second n-type semiconductor layer 4b is a third n-type semiconductor layer made of AlGaAs or the like, 5 is a second p-type semiconductor layer made of AlGaAs or the like, and 6 is a third p-type semiconductor layer made of GaAs or the like. 7 is an anode terminal, 8 is a gate terminal, and 9 is a cathode terminal.

  The energy gap (band gap energy) and carrier density of each of these semiconductor layers are preferably designed so as to increase the light receiving sensitivity of the light emitting thyristor, the light extraction efficiency to the outside, and the light emission efficiency. Specifically, the energy gap of the third n-type semiconductor layer 4b is larger than that of the second n-type semiconductor layer 4a, and the energy gap of the third n-type semiconductor layer 4b is larger than that of the second p-type semiconductor layer 5. The second p-type semiconductor layer 5 may have an energy gap larger than that of the first p-type semiconductor layer 3.

  With such an energy gap relationship, electrons and holes can be efficiently confined in the second p-type semiconductor layer 5 serving as a light emitting layer, and thus a light emitting thyristor with high internal quantum efficiency and high light emitting efficiency. Can be provided. Further, since the energy gap of the first p-type semiconductor layer 3 serving as the main light receiving layer is smaller than the energy of light emitted from the second p-type semiconductor layer 5 serving as the light emitting layer, adjacent light emitting thyristors emit light. A light-emitting thyristor that can efficiently receive light and has high light-receiving sensitivity can be provided.

  Here, the energy gap of the third p-type semiconductor layer 6 is smaller than that of other semiconductor layers in order to obtain an ohmic junction with the anode terminal 7. 3 is affected by the p-type semiconductor layer 6 because the thickness of this layer is usually very thin, 10 nm to 20 nm, so that the absorption of light emission from the second p-type semiconductor layer 5 which is the main light-emitting layer is negligible. is there.

  Further, by making the carrier density of the first p-type semiconductor layer 3 higher than the carrier density of the second n-type semiconductor layer 4a, the pn junction portion formed by these layers on the second n-type semiconductor layer 4a side. Since the depletion layer becomes thicker, the light receiving area can be increased, so that the light receiving sensitivity to the light applied to the semiconductor layer can be further improved.

  In addition, by making the carrier density of the third p-type semiconductor layer 6 higher than that of the second p-type semiconductor layer 5, the positive p-type semiconductor layer 5 that is the main light-emitting layer can be injected. Since the hole concentration can be increased and the ohmic resistance with the anode terminal 7 can also be reduced, high internal quantum efficiency in the second p-type semiconductor layer 5 which is the main light emitting layer, and good with the anode terminal 7 An ohmic junction can be obtained.

  Further, the energy gap of the first n-type semiconductor layer 2 is made larger than that of the first p-type semiconductor layer 3 and the second n-type semiconductor layer 4a, so that the first and second n-type semiconductor layers 2, 4a. In the phototransistor portion formed of the first p-type semiconductor layer 3, the current amplification factor is increased by increasing the injection efficiency of the emitter, so that light from the outside can be efficiently received. At this time, specifically, the energy gap of the first p-type semiconductor layer 3 is larger than the energy gap of the first and second n-type semiconductor layers 2 and 4a from the first p-type semiconductor layer 3 to the first. It is desirable that the hole be small so that injection of holes into the n-type semiconductor layer 2 is suppressed.

  Further, in this configuration, when the first p-type semiconductor layer 3 and the second n-type semiconductor layer 4a are made of GaAs, and the first n-type semiconductor layer 2 is made of InAlGaP or AlGaAs, the first p-type semiconductor is formed. Since the energy gap of the layer 3 is smaller than that of the first n-type semiconductor layer 2 and matching at the junction is improved, the first and second n-type semiconductor layers 2 and 4a and the first p-type In the phototransistor portion formed of the semiconductor layer 3, since the current amplification factor increases as the emitter injection efficiency increases, light from the outside can be efficiently received.

  In the light-emitting thyristor used in the light-emitting device of the present invention, the n-type semiconductor substrate 1 can grow a III / V group semiconductor layer or a II / VI group semiconductor layer. For example, GaAs, InP, GaP, Si, Ge Etc. When the cathode terminal 9 is formed on the first n-type semiconductor layer 2, an insulating substrate or a semi-insulating substrate can be used as the base substrate for the n-type semiconductor substrate 1. For example, GaAs, GaN, sapphire or the like may be used as a base substrate and an n-type semiconductor layer may be formed on the surface thereof.

The first n-type semiconductor layer 2 has an energy gap smaller than that of the second p-type semiconductor layer 5 which is a main light emitting layer, and has a carrier density of about 1 × 10 ¹⁸ cm ⁻³ . For example, GaAs, AlGaAs , InGaP or the like.

The first p-type semiconductor layer 3 has an energy gap smaller than that of the first n-type semiconductor layer 2, has a carrier density of about 1 × 10 ¹⁸ cm ⁻³ , and is made of, for example, AlGaAs or GaAs. In particular, when the thickness of this layer is 50 to 1000 mm, the current amplification factor of the phototransistor portion is increased, so that light from the outside can be efficiently received.

The second n-type semiconductor layer 4a has an energy gap smaller than that of the first n-type semiconductor layer 2, and the carrier density is the smallest among all layers, which is about 1 × 10 ¹⁶ cm ⁻³ to 1 × 10 ¹⁷ cm ^−3. For example, it is made of GaAs, AlGaAs or the like.

The third n-type semiconductor layer 4b has an energy gap larger than that of the second p-type semiconductor layer 5 and a carrier density of about 1 × 10 ¹⁷ to 1 × 10 ¹⁸ cm ⁻³ . For example, AlGaAs, InAlGaP Etc. In particular, when it is made of Al _y Ga _1-y As (0 <y ≦ 0.5), the electron carrier density can be increased, and more electrons can be injected into the second p-type semiconductor layer 5 which is the main light emitting layer. Therefore, the internal quantum efficiency can be increased.

The second p-type semiconductor layer 5 is a layer that becomes a main light-emitting layer and has a carrier density of about 1 × 10 ¹⁸ cm ⁻³ and is made of, for example, AlGaAs, InAlGaP, or the like. In particular, when it is made of Al _z Ga _1-z As (0 <z ≦ 0.3), it functions as a direct transition type semiconductor, so that high internal quantum efficiency can be obtained.

  Further, the second p-type semiconductor layer 5 may be formed by stacking a plurality of layers as shown in FIG. 1B, for example. In FIG. 1B, the second p-type semiconductor layer 5 is formed by sequentially stacking second p-type semiconductor layers 5a, 5b, and 5c on the third n-type semiconductor layer 4b.

  Here, by enlarging the energy gap of the second p-type semiconductor layers 5b and 5c as compared with the second p-type semiconductor layer 5a, the effect of confining electrons and holes in the second p-type semiconductor layer 5a can be obtained. Since it can be increased, the internal quantum efficiency is high and the light emitting thyristor has high light emission efficiency. The energy gap between the second p-type semiconductor layers 5b and 5c is substantially equal to that of the third n-type semiconductor layer 4b and is larger than that of the second p-type semiconductor layer 5a, so that the main light emitting layer is obtained. Since the second p-type semiconductor layers 5b and 5c can be regarded as transparent with respect to light emission from the second p-type semiconductor layer 5a, the light generated in the second p-type semiconductor layer 5a is transmitted to the second p-type semiconductor layer 5a. Absorption by the type semiconductor layers 5b and 5c is eliminated, and the light extraction efficiency to the outside can be increased.

  In addition, since the hole carrier density is increased in the order of the second p-type semiconductor layers 5a, 5b, and 5c, more holes can be injected into the second p-type semiconductor layer 5a serving as the main light emitting layer. The internal quantum efficiency can be increased.

Such second p-type semiconductor layers 5a, 5b, 5c may have carrier densities of about 1 × 10 ¹⁸ cm ⁻³ , 5 × 10 ¹⁸ cm ⁻³ , and 1 × 10 ¹⁹ cm ^{−3 in} order. For example, it is made of AlGaAs, InAlGaP or the like. In particular, if the second p-type semiconductor layer 5a is made of Al _z Ga _1-z As (0 <z ≦ 0.3), the second p-type semiconductor layer 5a functions as a direct transition type semiconductor, and the second p-type semiconductor layer 5b, In 5c, if it is made of Al _y Ga _1-y As (0 <y ≦ 0.5), the hole carrier density can be increased, and therefore the internal quantum efficiency is high.

The third p-type semiconductor layer 6 is a layer for performing ohmic contact with the anode terminal 7 and has a carrier density of 1 × 10 ¹⁹ cm ⁻³ or more. For example, GaAs, InGaP, etc. Consists of.

  The anode terminal 7 functions as an anode electrode by ohmic contact with the third p-type semiconductor layer 6 and is made of, for example, Au, AuGe, AuZn, or the like.

  The gate terminal 8 has an ohmic contact with the second n-type semiconductor layer 4a and functions as a gate electrode in the thyristor, and is made of, for example, Au, AuGe, Ni, or the like.

  The cathode terminal 9 functions as a cathode electrode by making ohmic contact with the n-type semiconductor substrate 1 or the first n-type semiconductor layer 2 and is made of, for example, Au, AuGe, Ni, or the like.

  In the light emitting thyristor thus formed, the second configuration is applied by applying, for example, a voltage having a value larger than the threshold voltage between the anode terminal 7 and the cathode terminal 9 to the above configuration. The p-type semiconductor layer 5 emits light mainly, and the photocurrent is received by receiving light in the phototransistor portion composed of the first and second n-type semiconductor layers 2, 4 a and the first p-type semiconductor layer 3. Since it flows, the threshold voltage or threshold current of light emission decreases.

  As described above, according to the light-emitting thyristor having the above-described configuration, a light-emitting thyristor having high light extraction efficiency and high light-receiving sensitivity can be obtained.

  Next, FIG. 2 is a plan view showing an example of an embodiment of a light-emitting device according to the present invention, comprising a three-terminal light-emitting switch element array 16 and a three-terminal light-emitting element array 15 in which transfer switch elements by light excitation are integrated. 3A is a cross-sectional view taken along line AA ′ in FIG. 2, and FIG. 3B is a cross-sectional view taken along line BB ′ in FIG.

  As shown in FIGS. 2 and 3, the light emitting device of the present invention can control the threshold voltage or threshold current of light emission by irradiating light from the outside, the anode terminal 7, the cathode terminal 9, and the gate terminal 8. Are arranged in a straight line so that light emitted from one three-terminal light-emitting switch element is incident on an adjacent three-terminal light-emitting switch element. A three-terminal light emitting switch element array 16 having a clock line (φ1, φ2) 13 connected to the anode terminal 7 and an anode capable of electrically controlling the threshold voltage or threshold current of light emission from the outside via the gate terminal 8 A number of three-terminal light-emitting elements each having a terminal 7, a cathode terminal, and a gate terminal 8 are arranged corresponding to the three-terminal light-emitting switch elements, and the three-terminal light-emitting elements The gate terminals 8 are electrically connected to the gate terminals 8 of the corresponding three-terminal light emitting switch elements, and the anode terminals 7 of the three-terminal light emitting elements are connected to a line (φI) 12 for supplying voltage or current for light emission. The three-terminal light-emitting element array 15 is provided, and the three-terminal light-emitting switch element and the three-terminal light-emitting element are respectively provided on the n-type semiconductor substrate 1 with a first n-type semiconductor layer 2 and a first p-type semiconductor layer. 3 and the second n-type semiconductor layer 4a are sequentially stacked, and a light-emitting portion in which the third n-type semiconductor layer 4b and the second p-type semiconductor layer 5 are stacked on the light-receiving portion. The anode terminal 7 is provided on the third p-type semiconductor layer 6 stacked on the light emitting portion, and the cathode terminal 9 is provided on the n-type semiconductor substrate 1 or the first n-type semiconductor layer 2, in this example, the n-type semiconductor substrate 1. To the second or third n-type semiconductor layer 4a, 4b In this example, the gate terminal 8 is electrically connected to the second n-type semiconductor layer 4a, and the three-terminal light-emitting switch element has a light-emitting part on the light-receiving part from an adjacent three-terminal light-emitting switch element. Are arranged so as to be biased to the side opposite to the side on which the emitted light is incident.

  In this example, an element array using a light emitting thyristor as a light emitting element has a start switch thyristor 17 composed of a similar light emitting thyristor connected to a three-terminal light emitting switch element array 16 in which switch light emitting thyristors are linearly arranged. And a gate terminal 8 of the light-emitting thyristor as a corresponding three-terminal light-emitting switch element of each of the element arrays 15 and 16, and a portion of the three-terminal light-emitting element array 15 in which light-emitting light-emitting thyristors are linearly arranged. In this example, the gate terminal 8 of the light-emitting thyristor as a three-terminal light-emitting element is electrically connected by a wiring in which the gate terminals 8 are shared. The gate terminal of the light emitting thyristor serving as the start switch thyristor 17 is connected to the start pulse line φS as a signal input unit, and the anode terminal 7 is the anode terminal of each light emitting thyristor of the three-terminal light emitting switch element array 16. 7, two clock lines (φ1, φ2) 13 are alternately connected one by one. Further, in this example, the anode terminal 7 has a configuration in which a part of the line (φI) 12 and the clock line (φ1, φ2) 13 has the function.

  The three-terminal light-emitting switch element array 16 and the three-terminal light-emitting element array 15 are arranged in parallel on the substrate, for example, the n-type semiconductor substrate 1, so that an optical printer head for an electrophotographic image recording apparatus is provided. It is used for a light emitting device as a line head.

  Here, in the three-terminal light emitting switch element, in order to dispose the light emitting part on the light receiving part so as to be biased to the side opposite to the side on which the light emitted from the adjacent three terminal light emitting switch element is incident, each of the light emitting thyristors is configured. After the semiconductor layers 2 to 6 are sequentially stacked to form the three-terminal light-emitting switch element, the third light-emitting section on the side where the start switch thyristor 17 is disposed is exposed in each of the three-terminal light-emitting switch elements. The n-type semiconductor layer 4b and a part of the second and third p-type semiconductor layers 5 and 6 are removed by etching, or the respective semiconductor layers 2, 3, and 4a forming the light receiving portion are formed in order, respectively. In the three-terminal light emitting switch element, the third n-type semiconductor layer 4b and the second and third layers are exposed using a mask so as to expose the light receiving portion on the side where the start switch thyristor 17 is disposed. The p-type semiconductor layers 5 and 6 may be formed. In the three-terminal light emitting switch element from which a part of the light emitting part has been removed by etching, when the light emitting part is arranged on the light receiving part so as to be biased to the side opposite to the side on which light emitted from the adjacent three terminal light emitting switch element is incident. A part of the upper part of the second n-type semiconductor layer 4a constituting the light receiving part may be removed together with the light emitting part. The area where the light receiving portion is exposed in the three-terminal light-emitting switch element is preferably smaller in consideration of the light emission intensity, but is preferably larger in order to increase the light-receiving sensitivity in the three-terminal light-emitting switch element. Is done. Note that the third n-type semiconductor layer 4b, which is a part of the semiconductor layer constituting the light emitting portion, may be present on the light receiving portion on the side where the start switch thyristor 17 is disposed. Because the band gap of the third n-type semiconductor layer 4 b is larger than that of the second p-type semiconductor layer 5, the third n-type semiconductor layer 4 b with respect to the light generated in the second p-type semiconductor layer 5. This is because it can be regarded as transparent and does not decrease the light receiving sensitivity of the light receiving portion.

  In this way, in the three-terminal light emitting switch element, the light emitting part is arranged on the light receiving part so as to be biased to the side opposite to the side on which the light emitted from the adjacent three terminal light emitting switch element is incident. In addition to the light receiving part exposed on the side surface, it is possible to receive light even at a part where the light emitting part on the light receiving part is not arranged, so that the light receiving sensitivity is increased, and a highly sensitive light emitting device capable of operating even with weak light is provided. it can.

  The line (φI) 12, the clock line (φ1, φ2) 13, and the start pulse line φS are made of, for example, Au, AuGe, Ni, or the like.

  Reference numeral 10 denotes a metal layer of a single layer or a laminated structure for making an ohmic contact between the third p-type semiconductor layer 6 of the light emitting thyristor used in the three-terminal light emitting switch element array 16 and the clock line 13, It functions as the anode terminal 7 of the light emitting thyristor together with the clock line 13. In this example, the anode terminal 7 of the light-emitting thyristor used in the three-terminal light-emitting element array 15 is configured such that a part of a line (φI) 12 that supplies a voltage or current for light emission has its function. However, the light emitting thyristor may be provided with a metal layer for making ohmic contact between the third p-type semiconductor layer 6 and the line 12 and function as the anode terminal 7.

  Reference numeral 11 denotes an insulating layer for ensuring electrical insulation between the clock line 13 (7) or the line 12 (7) for supplying voltage or current for light emission and the metal layer 10 or each semiconductor layer. An insulating film having translucency and flatness such as conductive polyimide is used.

  The insulating layer 11 may be formed so as to fill in between the light emitting thyristors. When the insulating layer 11 is formed between the light emitting thyristors, it is easy to form the line (φI) 12, the clock line (φ1, φ2) 13, the start pulse line φS and the gate terminal 8, and the oxidation of each semiconductor layer. Can be prevented.

  Reference numeral 18 denotes a reflective layer that reflects light emitted from the light emitting part and is provided so as to cover the adjacent light emitting part and light receiving part of the three-terminal light emitting switch elements arranged in a straight line. The reflective layer 18 is made of an insulating material having a refractive index lower than that of the material constituting the insulating layer 11 that fills the space between the adjacent light emitting portion and light receiving portion of the three-terminal light emitting switch element, Cr, Au, AuGe, Al, etc. Using a metal material having a high reflectivity, a normal thin film may be formed. Here, when a conductive material is used for the reflective layer 18, for example, an insulating layer is formed so as to cover the three-terminal light emitting switch array 16 in which the clock line 13 is formed, and the conductive layer is provided thereon. It is necessary to ensure insulation from the clock line 13 by forming the reflective layer 18 made of a material. Alternatively, the reflective layer 18 may have a multilayer structure in which a layer made of a conductive material is formed on the insulating layer. Such an insulating layer may be formed by the same method using the same material as that of the insulating layer 11, for example.

  By providing the reflection layer 18 in this manner, the light leaking upward from the light emission part of one of the three-terminal light-emitting switch elements is reflected between adjacent three-terminal light-emitting switch elements. This is preferable because it can be efficiently guided to the light receiving portion of the other three-terminal light emitting switch element. Further, as shown in FIGS. 3 (a) and 3 (b), the reflective layer 18 is provided on the surface of the three-terminal light-emitting element array 15 side and the side of the three-terminal light-emitting element array 15 in each light-emitting thyristor of the three-terminal light-emitting switch element array 16. If it is formed so as to cover each semiconductor layer on the opposite surface, light emission from the three-terminal light-emitting switch element array 16 in the direction perpendicular to the surface of the substrate, light emission in the direction of the three-terminal light-emitting element, and three-terminal light emission This is preferable because light emitted in the opposite direction of the element can be reflected and efficiently guided to the light receiving portion.

  Further, when the clock line (φ1, φ2) 13 (7) is formed of a material having a high reflectivity such as Cr, Au, AuGe and Al, for example, the clock line (φ1, φ2) 13 is formed in the reflective layer 18. Of the light emitted from the light-emitting portion of one of the three-terminal light-emitting switch elements between the adjacent three-terminal light-emitting switch elements, the light leaking upward from the clock line (φ1, φ2) 13 (7) This is preferable because it can be reflected and efficiently guided to the light receiving portion of the other three-terminal light emitting switch element. Further, one clock line 13 (7) is adjacent to the other clock line 13 (7), the metal layer 10 or each semiconductor layer, and the insulating layer 11 so as to be electrically adjacent to the three-terminal light emitting switch element. If it is formed so as to cover the light emitting part and the light receiving part, the light emitted from the light emitting part of one of the three terminal light emitting switch elements by the one clock line 13 (7) is directed upward in the three terminal light emitting switch element array. The leakage light is reflected and can be efficiently guided to the light receiving portion of the other three-terminal light emitting switch element. In order to obtain such a configuration, for example, the insulating layer 11 is provided on the metal layer 10 except for the portion where the clock lines (φ1, φ2) 13 (7) are connected. After forming (7), the other clock line 13 (7) is covered and an insulating layer is provided except for the portion where one clock line 13 (7) is connected to the metal layer 10, and then this insulation is performed. One clock line 13 (7) may be formed so as to cover almost the entire surface of the conductive layer.

  Further, as shown in FIGS. 4 and 5, the light emission from the three-terminal light-emitting switch element particularly when the three-terminal light-emitting switch element array 16 and the three-terminal light-emitting element array 15 are arranged in parallel on the substrate. Among them, a light shielding layer 14 that shields light emitted in the vertical direction, light emitted in the direction of the three-terminal light-emitting element, and light emitted in the direction opposite to the three-terminal light-emitting element may be provided on the surface of the substrate.

  4 is a plan view showing another example of the light-emitting device of the present invention using the light-emitting thyristor having the layer structure shown in FIG. 1B, and FIG. 5A is a cross-sectional view taken along line AA ′ of FIG. FIG. 4B is a sectional view taken along the line BB ′ of FIG. Components having the same functions as those in FIGS. 1 to 3 are given the same reference numerals, and redundant descriptions are omitted.

  By providing such a light shielding layer 14, light leaking from the three-terminal light-emitting switch element array 16 is emitted in the direction perpendicular to the surface of the substrate, emitted in the direction of the three-terminal light-emitting element, and emitted in the direction opposite to the three-terminal light-emitting element. Is sufficiently shielded from light by the light-shielding layer 14. Therefore, when the light-emitting device of the present invention is used as an exposure device in an electrophotographic image recording apparatus, the image is not deteriorated due to such leakage light. Image quality can be obtained. Various materials can be used for the light shielding layer 14 as long as the light emitted from the three-terminal light emitting switch element can be absorbed almost completely with a thickness of about 2 to 3 μm. What is necessary is just to coat and process and form in a predetermined pattern by photoetching. The light shielding layer 14 may be made of the same material as that of the reflective layer 18 that reflects light emitted from the three-terminal light-emitting switch element toward the three-terminal light-emitting switch element.

  Next, FIG. 6 shows an equivalent circuit diagram showing a schematic circuit configuration of a basic structure in an example of an embodiment of a light emitting device of the present invention in which transfer switch elements by light excitation are integrated using the light emitting thyristor of the present invention. FIG. 6 shows a conceptual diagram of FIG.

  In the example shown in FIGS. 6 and 7, the light-emitting thyristors T0 to Tn of the present invention constituting the three-terminal light-emitting switch element array 16 and the light-emitting thyristors L1 to Ln of the present invention constituting the three-terminal light-emitting element array 15 are The gate terminals of the corresponding light emitting thyristors T1 to Tn and the gate terminals of the light emitting thyristors L1 to Ln of each element array are electrically connected (for example, The gate terminal of the i-th (i <n) light-emitting thyristor Ti of the three-terminal light-emitting switch element array 16 and the gate terminal of the i-th light-emitting thyristor Li of the three-terminal light-emitting element array 15 are connected. A start pulse line φS is connected to the gate terminal of the switch thyristor T0 for use as a signal input section. Two clock lines (φ1, φ2) are alternately connected to the anode terminals of the light-emitting thyristors of the three-terminal light-emitting switch element array 16 in sequence, including the start switch thyristor T0.

  Based on the example configured as described above, switching signal transfer and light emission operation in the light emitting device of the present invention will be described.

  The transfer of the switching signal is started by changing the clock line φ2 connected to the anode terminal of the start switch thyristor T0 to the high level, and changing the start pulse line φS from the high level to the low level (the gate satisfying the emission condition of the light emitting thyristor T0). It starts by changing to a voltage below the voltage. As a result, the start switch thyristor T0 is turned on to emit light. The light emitted from the start switch thyristor T0 is configured so that a part thereof is most strongly incident on the next light emitting thyristor T1, and the light emission threshold voltage of the light emitting thyristor T1 is reduced by this light irradiation. .

Next, transfer of the ON condition from the light emitting thyristor T0 to the light emitting thyristor T1 will be described. The light emission by the light emission from the light emitting thyristor T0 reduces the light emission threshold voltage of the light emitting thyristor T1, and in this state, the clock line φ1 connected to the gate terminal of the light emitting thyristor T1 is changed from the low level to the high level. . At this time, since the light emitting thyristor T3 having the same clock line φ1 connected to the gate terminal is sufficiently away from the start switch thyristor T0, the threshold voltage of light emission due to the light emission of the light emission of the start switch thyristor T0. There is almost no decline. Therefore, the high level V _H (φ1) of the clock line φ1 is set to a voltage between the light emission threshold voltage V _TH (T3) of the light emitting thyristor T3 and the light emission threshold voltage V _TH (T1) of the light emitting thyristor T1. If this is set (that is, if V _H (φ1) is set as V _TH (T1) <V _H (φ1) <V _TH (T3)), only the light-emitting thyristor T1 is turned on and emits light.

After the light emitting thyristor T1 is turned on and emits light, the light emitting thyristor T0 is turned off and the light emission ends by changing the clock line φ2 from the high level to the low level. Thus, the ON state of the light-emitting thyristors constituting the three-terminal light-emitting switch element array 16 is transferred from the start switch thyristor T0 to the next light-emitting thyristor T1. At this time, by changing the start pulse line φS from the low level to the high level, the start switch thyristor T0 remains off even if the clock line φ2 is changed to the high level again. Here, the line φI for supplying the voltage or current for light emission is changed from the low level to the high level. In the first light-emitting thyristor L1 of the three-terminal light-emitting element array 15, since the light-emitting thyristor T1 of the corresponding three-terminal light-emitting switch element array 16 is in the on state, the voltage applied to its gate terminal is almost 0V. The second light-emitting thyristor L2 of the array 15 has the corresponding light-emitting thyristor T2 of the three-terminal light-emitting switch element array 16 in the off (light-excited) state, and the first and second light-emitting thyristors L1 and L2 of the three-terminal light-emitting element array 15 Assuming that the threshold voltages of light emission are V _TH (L1) and V _TH (L2), respectively, the high level V _H (φI) of the clock line φI is V _TH (L1) <V _H (φI) <V as described above. If set to be _TH (L2), only the light-emitting thyristor L1 is turned on to emit light. When the line φI that supplies the voltage or current for light emission is changed from the high level to the low level, the first light-emitting thyristor L1 of the three-terminal light-emitting element array 15 is turned off and the light emission ends.

  Next, a method for transferring a switching signal in the three-terminal light emitting switch element array 16 will be described.

For example, when the light emitting thyristor T2 is in the light emitting state, the light emitted by the light emission is applied to the adjacent light emitting thyristors T1 and T3. Here, the light emitting thyristor T1 has a light emitting portion formed on the light receiving portion on the light emitting thyristor T2 side, and the light emitting thyristor T3 has no light emitting portion disposed on the light receiving portion on the light emitting thyristor T2 side and the light receiving portion is exposed. It is in a state. For this reason, the amount of light received by the light-emitting thyristor T3 becomes larger than that of the light-emitting thyristor T1 due to light emission of light emitted from the light-emitting thyristor T2, and as a result, the light emission threshold voltage of the light-emitting thyristor T3 is greatly reduced compared to the light-emitting thyristor T1. . Here, the high level V _H (φ1) of the clock line φ1 is a voltage between the light emission threshold voltage V _TH (T3) of the light emitting thyristor T3 and the light emission threshold voltage V _TH (T1) of the light emitting thyristor T1. (That is, if V _H (φ1) is set as V _TH (T3) <V _H (φ1) <V _TH (T1)), only the light emitting thyristor T3 is turned on and emits light. . In this way, on the light receiving part of the three-terminal light-emitting switch element, the light-emitting part is arranged so as to be biased to the side where the light emitted from the adjacent three-terminal light-emitting switch element enters, that is, the side opposite to the side where the switch thyristor T0 is arranged. Thus, the transfer direction of the switching signal can be designated in one direction of the light emitting thyristors T0 to Tn. That is, even if there are two clock lines, it can be transferred only to the light-emitting thyristor T3 next to the light-emitting thyristor T2, and by repeating this, it can be sequentially transferred to the light-emitting thyristors T3, T4, T5. .

  As described above, even if the transfer direction designation diode in the conventional second light emitting device is eliminated, the number of clock lines φ1 and φ2 remains two without increasing the number of new clock lines for determining the transfer direction of the light emission state. Since the transfer direction of the light emission state in the three-terminal light emitting switch element can also be controlled in one direction, the entire structure can be simplified.

  By sequentially repeating the switching signal transfer by the three-terminal light-emitting switch element array 16 and the light-emitting operation by the corresponding three-terminal light-emitting element array 15 as described above, the start switch thyristor T0 is turned on (light emission). State) is sequentially transferred to the light emitting thyristors T1, T2, T3... As a switching signal, and the light emitting operation of the light emitting thyristors L1, L2, L3.

  The light emission from each light-emitting thyristor T1, T2, T3... Of the three-terminal light-emitting switch element array 16 is not only in the direction toward the adjacent light-emitting thyristors arranged in a straight line, but also in the direction perpendicular to the surface of the substrate ( The light emitting thyristors T1, T2, T3... To the outside with respect to the surface of the substrate and the light emitting thyristors T1, T2, T3. This also occurs in the direction toward the light emitting thyristors L1, L2, L3... Of the provided three-terminal light emitting element array 15.

  Therefore, the light leaked in the direction perpendicular to the surface of the substrate, that is, the upward direction of the three-terminal light-emitting switch array 16 between the adjacent three-terminal light-emitting switch elements is reflected by providing a reflective layer 18 as shown in FIGS. It is preferable to make it. As a result, light leaking upward from the light emitting portion of one of the three terminal light emitting switch elements is reflected between the adjacent three terminal light emitting switch elements, and the other three terminal light emission is reflected. Since the light can be efficiently guided to the light receiving portion of the switch element, the light emitting device has high light receiving sensitivity.

  As such a reflective layer 18, a material having a lower refractive index or a material having a higher reflectance than the insulating layer 11 that fills the space between the light receiving portion and the adjacent light receiving portion of the three-terminal light emitting switch element can be used. For example, a multilayer film made of polyimide and Cr may be used as the reflective layer 18, and polyimide may be formed by spin coating and Cr may be laminated by a method of forming an ordinary thin film.

  Further, the clock line 13 may be made of a material having a high reflectance so that the clock line 13 has the function of the reflective layer 18. Here, only the clock line 13 may be used as the reflective layer 18, or the reflective layer 18 may be provided so as to cover the light receiving unit and the light emitting unit adjacent to the three-terminal light emitting switch element together with the clock line 13. If only 13 is used as the reflective layer 18, a light emitting device with high light receiving sensitivity can be formed without forming a new reflective layer 18, which is preferable.

  Further, light emission in the direction perpendicular to the surface of the substrate, light emission in the direction of the three-terminal light-emitting element, and light emission in the opposite direction of the three-terminal light-emitting element may cause image noise in image recording as bias light from the light-emitting device, There may be noise that causes a malfunction with respect to light emission of the three-terminal light emitting element. Therefore, it is preferable to provide light shielding in the direction perpendicular to the surface of the substrate and light emission in the direction of the three-terminal light emitting element by providing a light shielding layer 14 as shown in FIGS. As a result, light leaking from the three-terminal light-emitting switch element array 16 can be reliably shielded by the light-shielding film 14, so light emission that does not deteriorate image quality due to such leaked light and can obtain excellent image quality It becomes a device.

  As such a light shielding layer 14, various materials can be used as long as the light emitted from the three-terminal light emitting switch element is almost completely absorbed with a thickness of about 2 to 3 μm. For example, polyimide or the like can be used. The film may be formed by spin coating and processing into a predetermined pattern by photoetching.

  4 and 5, the metal layer 10 located on the semiconductor layer of the light emitting thyristor is used as a light shielding layer for light emission perpendicular to the surface of the substrate. As a light shielding layer for light emission in the direction of the three-terminal light-emitting element, a conductive layer in which the gate terminal 8 of the light-emitting thyristor as the three-terminal light-emitting switch element and the gate terminal 8 of the light-emitting thyristor as the three-terminal light-emitting element are used in common is used. be able to.

  Further, as shown in FIG. 5, the anode terminal 7 of the light-emitting thyristor as a three-terminal light-emitting switching element is constituted by a metal layer 10 formed so as to cover almost the entire surface of the third p-type semiconductor layer 6, whereby this metal The layer 10 can be used as a light-shielding layer that shields light emitted in the direction perpendicular to the surface of the substrate, and the electric field to the semiconductor layer can be made uniform, thereby increasing the emission intensity radiated in the lateral direction of the stacked semiconductor layers. Can do.

  Further, as shown in FIG. 5A, in the three-terminal light-emitting switch element, the light shielding layer 14 (this example) is formed on the wall surface of the light-emitting section on the light-receiving section on the side where the light emitted from the adjacent three-terminal light-emitting switch element is incident. Then, by forming the metal layer 10) having the function of the light shielding layer 14 formed on the wall surface of the light emitting portion through the insulating layer 11, the three-terminal light emitting switching element arranged opposite to the transfer direction of the switching signal is provided. Since light emission can be prevented, the transfer direction of the switching signal can be more reliably controlled in one direction.

  The image forming apparatus of the present invention is an electrophotographic image forming apparatus in which the light emitting device of the present invention is used as an exposure device for a photoreceptor. The configuration example includes, for example, a photoconductor, a charging device, an exposure device, a developing device, a transfer device, and a fixing device, and the exposure device for the photoconductor is a three-terminal light emitting switch using the light emitting thyristor of the present invention. An array in which elements and three-terminal light-emitting elements are integrated is linearly arranged on a circuit board to form a light-emitting device having a three-terminal light-emitting switch element array 16 and a three-terminal light-emitting element array 15, respectively. A driver IC is mounted on the board.

  According to the image forming apparatus of the present invention having such a configuration, since the light emitting device of the present invention is used in the exposure device for the photosensitive member, the three-terminal light emitting switch element and the three terminal light emitting by the light emitting thyristor of the present invention are used. An exposure apparatus can be manufactured at low cost by using an array in which elements are integrated, and since no bias light or leakage light is generated from the exposure apparatus, an image provided with an exposure apparatus capable of forming an inexpensive and high-quality image. A forming apparatus can be provided.

  The present invention is not limited to the embodiments described above, and various changes and improvements can be made without departing from the scope of the present invention.

  For example, in the example of the above embodiment, two clock lines 13 are provided, but three or more clock lines 13 may be provided. By providing three or more clock lines 13, the direction in which the switching signal is transferred in the three-terminal light emitting switch element array 16 can be controlled more reliably.

(A) is sectional drawing which shows an example of the layer structure of the light emitting thyristor used for the light-emitting device of this invention, (b) is sectional drawing which shows the other example of the layer structure of a light emitting thyristor. Embodiment of Light-Emitting Device of the Present Invention Comprising a Three-Terminal Light-Emitting Switch Element Array 16 and a Three-Terminal Light-Emitting Element Array 15 Constructed by Using Light-Emitting Thyristors of the Present Invention It is a top view which shows an example. (A) is the sectional view on the A-A 'line of FIG. 2, (b) is the sectional view on the B-B' line of FIG. It is a top view which shows the other example of embodiment of the light-emitting device of this invention using the light emitting thyristor of the layer structure shown in FIG.1 (b) of this invention. (A) is the sectional view on the A-A 'line of FIG. 4, (b) is the sectional view on the B-B' line of FIG. It is an equivalent circuit diagram which shows the schematic circuit structure of the basic structure in an example of embodiment of the light-emitting device of this invention. FIG. 7 is a conceptual diagram of FIG. 6. It is sectional drawing which shows the basic structure of the conventional light emitting thyristor, and the diagram which shows the state of the carrier density of each layer. It is a diagram which shows typically the current-voltage characteristic of a light emitting thyristor. It is the equivalent circuit diagram which shows the schematic circuit structure of the basic structure of the conventional 1st light-emitting device, and the diagram which shows the waveform of each clock pulse light emission intensity. It is an equivalent circuit diagram which shows the schematic circuit structure of the basic structure of the conventional 2nd light-emitting device.

Explanation of symbols

DESCRIPTION OF SYMBOLS 1 ... N-type semiconductor substrate 2 ... 1st n-type semiconductor layer 3 ... 1st p-type semiconductor layer 4a .. 2nd n-type semiconductor layer 4b .. 3rd n-type semiconductor layer 5 ... Second p-type semiconductor layer 6 ... Third p-type semiconductor layer 7 ... Anode terminal 8 ... Gate terminal 9 ... Cathode terminal
10 ... Metal layer
14 ... Light shielding layer
15 ... 3 terminal light emitting element array
16 ... 3 terminal light emitting switch element array
18 ... Reflective layer T0, T1, T2, T3 to Tn ... Light-emitting thyristor (3-terminal light-emitting switch element)
L1, L2, L3 to Ln ... Light-emitting thyristor (3-terminal light-emitting element)
φ1, φ2 ・ ・ ・ Clock line φI ・ ・ ・ Line for supplying voltage or current for light emission

Claims (5)

A large number of three-terminal light-emitting switch elements having an anode terminal, a cathode terminal, and a gate terminal, each of which can control a light-emission threshold voltage or a threshold current by irradiating light from the outside. A three-terminal light-emitting switch element array that is arranged in a straight line so that light emitted from the three-terminal light-emitting elements is incident on the adjacent three-terminal switch elements, and a clock line is connected to each anode terminal of the three-terminal light-emitting switch elements;
A number of three-terminal light-emitting elements having an anode terminal, a cathode terminal, and the gate terminal, the threshold voltage or threshold current of light emission being electrically controllable from the outside via the gate terminal, the three-terminal light-emitting switch element The gate terminals of the three-terminal light-emitting elements are electrically connected to the gate terminals of the corresponding three-terminal light-emitting switch elements, and the anode terminals of the three-terminal light-emitting elements emit light. A three-terminal light emitting element array connected to a line for supplying voltage or current for
The three-terminal light-emitting switch element and the three-terminal light-emitting element are each formed by sequentially stacking a first n-type semiconductor layer, a first p-type semiconductor layer, and a second n-type semiconductor layer on an n-type semiconductor substrate. And a light emitting portion in which a third n-type semiconductor layer and a second p-type semiconductor layer are stacked on the light-receiving portion, and the anode terminal is connected to the second p-type semiconductor layer. A light emitting thyristor in which the cathode terminal is electrically connected to the n-type semiconductor substrate or the first n-type semiconductor layer, and the gate terminal is electrically connected to the second or third n-type semiconductor layer.
The three-terminal light-emitting switch element is characterized in that the light-emitting part is arranged on the light-receiving part so as to be biased to the side opposite to the side on which light emitted from the adjacent three-terminal light-emitting switch element is incident. . The reflective layer which reflects the said light emission is provided so that the said light emission part and the said light-receiving part which the said 3 terminal light emission switch element arranged in a straight line may adjoin may be provided. Light emitting device. The light emitting device according to claim 2, wherein the clock line also serves as the reflective layer. The three-terminal light-emitting switch element array and the three-terminal light-emitting element array are arranged in parallel on the substrate, and light emitted from the three-terminal light-emitting switch element in a direction perpendicular to the surface of the substrate The light-emitting device according to any one of claims 1 to 3, further comprising a light-shielding layer that shields light emitted in the direction of the three-terminal light-emitting element and light emitted in a direction opposite to the three-terminal light-emitting element. 5. An image recording apparatus, wherein the light emitting device according to claim 1 is used in an exposure device for a photosensitive member.

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