JPH0752590B2 - Driving method for semiconductor optical memory - Google Patents

Description

The present invention relates to a method for driving a semiconductor optical memory required for image processing, optical logic operation and the like.

[Conventional technology]

In the fields of optical computers, optical switching, and optical / electrical integrated circuits, pnpn junction devices used as optical memory devices have been attracting attention (for example, J. Appl. Phy. 59 (2) 1986,
pp596-600). FIG. 4 shows a sectional view of an element having a conventionally known structure. In the figure, this pnpn junction element is an n-type Ga
N-Al with n-type impurity concentration of 5 × 10 ¹⁷ cm ^-3 on As substrate 1
_0.4 Ga _0.6 As layer 2 1 μm, p-type impurity concentration 1 × 10 ¹⁹ cm ^-3
The p-GaAs layer 3 of 50 Å, the n-type has an impurity concentration of 1 × 10 ¹⁷ cm ^-3 of the n-GaAs (light-emitting layer) 4 μm, and the p-type has an impurity concentration of 5 × 10 7.
MBE of an ¹⁸ cm ⁻³ p-Al _0.4 Ga _0.6 As layer 5 of 1 μm and a p-type impurity concentration of 1 × 10 ¹⁹ cm ⁻³ p-GaAs layer 6 of 0.1 μm.
It grows continuously by the method. Using the obtained wafer, AuZn
When the p-type electrode 7 and the n-type electrode 8 are formed in the ring shape and the AuGeNi alloy, respectively, the pnpn junction element shown in FIG. 4 is obtained.

A semiconductor structure having such a pnpn junction has a switching function. It is known that this switching voltage shifts to the low voltage side when weak light is incident. The bias voltage is set to a voltage slightly lower than the switching voltage, and when weak light enters, it is possible to switch from the off state to the on state. When switched to the on state, all pn junctions are forward biased and emit light. At this time, a strong light output intensity can be obtained by selecting the magnitude of the load resistance. Further, since the forward bias state is maintained even after the incident light is cut off, it can be used as a kind of optical memory. In this conventional example, both light emission and light reception are performed in the n-GaAs layer 4.

A semiconductor optical memory is formed by integrating the above optical memory devices on the same substrate.

In such a semiconductor optical memory, a weighted storage function having different sensitivity depending on location is important for application. In order to realize such a weighted storage function, it is necessary to change the voltage level of the applied drive pulse. The current-voltage characteristics of the optical memory device are shown in FIG. In FIG. 5, in the state 10 where light is not incident on the optical memory element, the switching of the optical memory element occurs when the applied voltage is equal to or higher than the switching voltage V _s . In the state 11 when "incident light amount 1" is incident on this optical memory element, switching occurs at a voltage V ₁ lower than V _s , and in the condition 12 where "incident light amount 2" having a larger light amount than "incident light amount 1" is incident. Switching occurs at a voltage V ₂ which is lower than the voltage V ₁ . Therefore, it is possible to realize an optical memory element in which writing is weighted and an element that is easy to store and an element that is hard to store are formed on the same substrate with the same structure. That is, by applying a voltage V _{3 such} that V ₂ <V ₃ <V ₁ to the optical memory element, it can be turned on by the light of “incident light intensity 2”, but the optical memory element is turned on by the light of “incident light intensity 1”. I can't remember it. Also
By applying a voltage V _{4 such} that V ₁ <V ₄ <V _s to the optical memory element, the ON state can be obtained with either the “incident light amount 1” or the “incident light amount 2”. Therefore, the applied voltage of V _{3 and} the applied voltage of V ₄ shown in FIG. 5 are added to the optical memory device formed with the structure of FIG. 4 on the same substrate, and the light of “incident light amount 1” is incident. As a result, only the element with the applied voltage of V ₄ can be turned on. In this way, the photosensitivity of the optical memory element is changed, and it is possible to weight the writing of optical data.

[Problems to be solved by the invention]

However, in order to realize weighted storage using such a driving method, there has been a problem that the power supply configuration becomes complicated. That is, a plurality of optical memory elements cannot be driven by a common power source because the voltages are individually changed, and power sources are required for the number of optical memory elements. Further, it is necessary to determine and control each power supply voltage. Furthermore, in order to make the current (output light intensity) that flows in the ON state at a bias voltage different from the voltages V ₃ and V ₄ constant (I ₁ ), as shown in FIG. It was also necessary to switch the “load line 2” 14. Therefore, in such a driving method, for example, 100 × 100 matrix, 1000
Assuming a large-capacity optical memory such as a × 1000 matrix, it would be complicated to add the weighting function described above, and it was almost impossible to realize it.

An object of the present invention is to realize a function of weighting the writing of the memory of the semiconductor optical memory without requiring a complicated power source.

[Means for solving problems]

The present invention relates to an optical memory having a light emitting layer having a first forbidden band width inside a pnpn junction device, and a semiconductor layer having a forbidden band width wider than the first forbidden band width sandwiching both sides of the light emitting layer. In a method for driving a semiconductor optical memory, wherein a plurality of elements are separated on at least a cathode layer or an anode layer and formed on the same substrate, and each light emitting layer and light receiving layer are formed on substantially the same substrate. A method for driving a semiconductor optical memory, characterized in that the optical information and the stored data of an adjacent optical memory element are simultaneously entered in time with a write pulse of the optical memory element for writing the optical information.

[Action]

According to the above means, the pn forming the semiconductor memory is
When the pn optical memory is turned on and emits light, light generated in the vertical and horizontal directions with respect to the light emitting layer of the device is used to store the stored data of the adjacent optical memory device at the timing when the optical information is incident. The simultaneous incidence allows the weighting of writing depending on the presence or absence of stored data.

〔Example〕

Hereinafter, embodiments of the present invention will be described in detail with reference to the drawings. FIG. 1 is a schematic sectional view of a semiconductor optical memory for explaining the operation of the present invention. The optical memory device 21 has the same structure as that shown in FIG. 4, and has an attached memory device 22 in parallel on the substrate 1 adjacent thereto. Fourth
The same components as those of the laminated structure shown in the figure are designated by the same reference numerals and the description thereof will be omitted. This attached memory element 22 has the same layer structure as the optical memory element 21, and is an n-GaAs that emits and receives light.
The (light emitting layer) 4 is on the same plane, and a light entrance / exit window in a direction perpendicular to the light emitting layer 4 is not provided, and the element size is smaller than the optical memory element 21.

FIG. 2 shows a plan view and a drive circuit schematic diagram of a semiconductor optical memory in which the elements of FIG. 1 are formed in a 2 × 2 matrix. As shown in FIG. 2, power supplies 19 and 20 and load resistors 17 and 18 are connected in series to each optical memory device and the accessory device. As shown in FIG. 1, the optical information 9 is incident on the optical memory element 21, and this is turned on, and the optical information output 15 in the horizontal direction at that time allows the optical information to be transferred and stored in the attached memory element 22. it can. Using this, weighted writing was performed.

FIG. 3A shows the applied voltage (a) to the optical memory device and the applied voltage (b) to the attached memory device. FIG. 3B shows A element 23, B element 25, C element 2 shown in FIG.
7 shows the relationship between the incident light amount of the optical information on the D element 29 and the incident timing. FIG. 3C shows the output of optical information from the optical memory element at each timing. The applied voltage shown in (a) of FIG. 3 (a) was supplied from the power supply 20, and the applied voltage shown in (b) of FIG. 3 (b) was supplied from the power supply 19. Voltage V ₃
Is the voltage shown in FIG. 5, the voltage V ₅ is a voltage slightly higher than the holding voltage V _h (V _h <V ₅ <V ₂ ), and the voltage V ₆ is a negative voltage.

In FIG. 3C, initial data is written in the A element 23 and the D element 29, and weighted higher than other elements. Therefore, as shown in (a) of FIG. 3 (a) and (a) of FIG. 3 (b), at t ₁ , the “incident light amount 2” shown in FIG. Light information for writing 33 having a light quantity is incident. A set pulse 31 for both writing and reading is applied to the optical memory element at the timing t ₁ and the A element 23 and the D element 29 are turned on ((a) in FIG. 3C). At that time, as shown in (b) of FIG. 3 (a), a set pulse is also applied to the attached memory element at the timing t _1.
34 is applied, and according to the optical information 15 in the horizontal direction of the optical memory device 21 shown in FIG. 1, the A auxiliary device 24 shown in FIG.
Optical information can be stored in the D attachment element 30. After that, by the reset pulse 32 shown in (a) of FIG.
3. The memory of the D element 29 is erased. Therefore, the writing optical information 33 shown in FIG. 3B remains only in the A attached element 24 and the D attached element 30 in FIG. The memory is held by the bias 35 shown in FIG.

Then the optical information 36 A device having a light intensity of FIG. 3 shown in FIG. 5 at a timing t ₂ as shown in (b) "the amount of incident light 1"
23, incident on the B element 25. At that time, as shown in FIG. 5, since the voltage V ₃ is applied to the optical memory element, it cannot be turned on by the light having the “incident light intensity 1”.
The B element 25 shown in the figure remains in the OFF state. However, the A element 23 shown in FIG.
ON to enter as horizontal optical information 15 shown in the figure
It can be in a state ((b) of FIG. 3 (c)). Then, as shown in (a) of FIG.
The memory of the A element 23 is erased by 32. Similarly, and C elements 27 t ₃ the B element 25 as shown in FIG. 3 (b), t ₄
In C element 27 and D element 29, in t ₅ , D element 29 and A element
Optical information having a light amount of “incident light amount 1” is incident on 23 and 23.
The A element 23 and the D element 29 can be in the ON state, and the others remain in the OFF state ((c) of FIG. 3 (c),
(D), (e)). As a result, as shown in FIG. 3C, only the A element 23 and the D element 29 in which the initial data is written are turned on by the same optical information, and the others are kept in the off state.

By the above, 8 pnpn optical memory devices (optical memory device 4
It was possible to give a learning function to each of the two, and four attached memory elements) by using two power supplies. The load resistor 17 shown in FIG. 2 is provided to change the intensity of the optical information output, and the load resistor 18 is provided to change the contribution of the initial memory by changing the resistance value.

In this embodiment, two pnpn optical memory elements (one optical memory element and one attached memory element) are used as one optical memory element, but the number is not particularly limited. Further, driving with eight optical memory elements is shown, but this is not particularly limited to the number.

〔The invention's effect〕

As described above, according to the present invention, regarding the driving of the semiconductor optical memory required for image processing, optical logic operation, etc., the optical information and the adjacent optical memory element are synchronized with the write pulse of the optical memory element for writing the optical information. By simultaneously inputting the stored data and the stored data, the function of weighting the writing of the storage of the semiconductor optical memory can be realized without requiring a complicated power source.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a semiconductor optical memory for explaining the effect of the present invention, FIG. 2 is a plan view schematically showing a drive circuit of the semiconductor optical memory of this embodiment, and FIG. (A) and (b) are diagrams showing applied voltages to the optical memory element and the attached memory element, and (a) to (d) of FIG. 3B are incident light amounts and incidences of optical information to the optical memory element. FIG. 3 is a diagram showing a timing relationship, FIGS. 3 (a) to 3 (e) are diagrams showing the output of optical information from the optical memory element at each timing, and FIG. 4 is a semiconductor optical diagram for explaining the prior art. FIG. 5 is a schematic sectional view of the memory, and FIG. 5 is a diagram showing current-voltage characteristics of the optical memory element. 1 …… n-GaAs substrate, 2 …… n-Al _0.4 Ga _0.6 As layer 3,6 …… p-GaAs layer, 4 …… n-GaAs (light emitting layer) 5 …… p-Al _0.4 Ga _0.6 As layer , 7 …… p-type electrode 8 …… n-type electrode, 9,15,16,36 …… optical information 13,14 …… load line, 17,18 …… load resistance 19,20 …… power supply, 21 …… Optical memory device 22 …… Attached memory device, 23 …… A device 24 …… A device, 25 …… B device 26 …… B device, 27 …… C device 28 …… C device, 29 …… D Element 30 …… D accessory element, 31,34 …… Set pulse 32 …… Reset pulse, 33 …… Light information for writing 35 …… Bias

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Claims (1)

[Claims] 1. A pnpn junction element having a light emitting layer having a first forbidden band width, wherein both sides of the light emitting layer are sandwiched by semiconductor layers having a forbidden band width wider than the first forbidden band width. Driving of an optical memory device in which a plurality of optical memory devices are formed on the same substrate by separating at least a portion other than a cathode layer or an anode layer, and each light emitting layer and light receiving layer are formed on almost the same substrate. In the method, a method for driving a semiconductor optical memory is characterized in that the optical information and the stored data of an adjacent optical memory element are simultaneously made incident in time with a write pulse of the optical memory element for writing the optical information.