JPH0752591B2 - 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 attracted attention (for example, J. Appl. Phy. 59 (2) 1986, pp.
596-600). 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
On As substrate 1, n-Al with n-type and impurity concentration of 5 × 10 ¹⁷ cm ^-3
_0.4 Ga _0.6 As layer 2 1 μm, p-type impurity concentration 1 × 10 ¹⁹ cm ^-3
P-GaAs layer 3 of 50 Å, n-type with an impurity concentration of 1 × 10 ¹⁷ cm ^-3 n-
The GaAs light-emitting layer 4 is 1 μm, p-type and has an impurity concentration of 5 × 10 ¹⁸ cm ^-3 .
-Al _0.4 Ga _0.6 As layer 5 1 μm, p-type impurity concentration 1 × 10 ¹⁹ cm
^-3 p-GaAs layer 6 of 0.1 μm is continuously grown by the MBE method. Using the obtained wafer, a p-type electrode 7 and an n-type electrode 8 are formed in a ring shape by AuZn alloy and AuGeNi, respectively, to obtain the pnpn junction element shown in FIG.

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.

In such a semiconductor optical memory, optical information can be transferred in the direction perpendicular to the light emitting layer 4. Fifth
Explaining in the figure, a write pulse is applied at the timing when the optical information 9 enters the optical memory element 14. As a result, the optical memory device 14 is turned on and stores optical information. Here, since the optical information is inputted / outputted to / from the light emitting layer 4 only in the vertical direction, it can be easily transferred to the optical memory element 15 vertically stacked on the optical memory element 14.

[Problems to be solved by the invention]

However, for transfer to other elements (optical memory elements 16 and 17), a special device (mirror, optical waveguide, optical switch, etc.) that changes the optical path in accordance with the timing of optical information transfer is required. Considering the use as an optical memory, it is important to have a large capacity.
As the number of optical memory devices such as 00x1000 matrix increases, not only the device becomes complicated and expensive, but also the driving method of the optical memory becomes complicated. There was a problem that it could not be transferred.

It is an object of the present invention to provide a driving method that can transfer information to an arbitrary memory element in a semiconductor memory arranged on a surface and does not require a complicated optical path changing device.

[Means for solving problems]

The present invention provides 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 sandwiching both sides of the light emitting layer. In a method for driving a semiconductor optical memory, wherein at least the elements other than the cathode layer or the anode layer are separated and a plurality of the elements are formed on the same substrate, and each light emitting layer and light receiving layer are formed on substantially the same plane, A method for driving a semiconductor optical memory, characterized in that a write pulse is applied to an adjacent optical memory element in synchronization with a read pulse of an optical memory element having optical information.

[Action]

According to the above means, the pn forming the semiconductor memory is
When one of the pn optical memory devices emits light in the ON state, light is generated in two directions, a vertical direction and a horizontal direction, in the light emitting layer of the device. Is injected into the light-receiving layer of the adjacent optical memory device and the write pulse is applied to the adjacent optical memory device at the timing to easily store the optical information in the horizontal direction on the surface of the semiconductor optical memory and to any device. Can be transferred.

〔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. Optical memory device 20,21
Has the same structure as that shown in FIGS. The same components as those of the laminated structure shown in FIGS. 4 and 5 are designated by the same reference numerals and the description thereof will be omitted. FIG. 2 is a plan view of the semiconductor optical memory shown in FIG. Each optical memory device 20
Nos. 23 to 23 are arranged at positions of 1st row, 2nd row, A column, and B column, respectively. Below A-1 element 20, A-2 element 21, B-1 element 22, B-2 element
Each element is distinguished as 23. FIG. 3 is a diagram showing applied voltages for driving each optical memory element of the semiconductor optical memory shown in FIG.

The switching voltage of each optical memory element is V _S and the holding voltage is V _h . Optical information is stored in the A-1 element 20 in FIG. In FIG. 3 (a), the optical information 9 indicates time.
It is incident on the A-1 element 20 at the timing of t ₁ . Write pulse (1) (V _h <V
₁ <V _S ) 30 is applied. As a result, the A-1 element 20 has optical information. Bias until time t ₂ (V _h <V ₂ <V ₁ <
The stored optical information is retained by applying V _S ) 31, and the optical information 10,1 is read by the read pulse (1) 32 at time t _2.
1 is read. As shown in FIG. 3 (b), the write pulse (2) 34 is applied to the A-2 element 21 at the time t ₂ according to the timing. A-2 by the optical information 11 shown in FIG. 1 and the write pulse (2) 34 shown in FIG.
Optical information is stored in the element 21. In Fig. 3 (b), A-
The optical information by applying a bias 35 to the time t ₃ to the second element 21 is held, the first view by the read pulse (3) 36 to time t _3, the optical information 18 and 19 are read out in the second view. Further, after the reading, the optical information of the A-2 element 21 is erased by the reset pulse (2) (V ₃ <0) 41 shown in FIG. 3 (b). At time t ₃ as shown in FIG. 3 (d) B-
A write pulse (3) 37 is applied to the two elements 23. Optical information is stored in the B-2 element 23 by the optical information 19 shown in FIG. 2 and the write pulse (3) 37 shown in FIG. Third
As shown in FIGS. (A) and (d), A-1 element 20 and B-2 element 23
The stored optical information is retained by applying the biases 43 and 38 until time t ₄ at time t _4, and the read pulse (2) 33 and the read pulse (4) 39 are transferred to the A-1 element 20, B-2 at time t _4. The optical information is applied to the element 23, and the optical information is transmitted to the element A 20
And B-2 element 23 can be simultaneously taken out. After reading the optical information as shown in FIGS. 3 (a) and 3 (d), the reset pulse (1) 40 and the reset pulse (3) 42 are used to output light from the A-1 element 20 and the B-2 element 23. Information storage is erased. The present invention can also be used in a spatial modulator for optical switching.

In the conventional semiconductor memory driving method, optical information could not be actually transferred to an element other than an optical memory element having optical information and a vertically stacked element. For example, optical information can be easily transferred to any optical memory device in the semiconductor optical memory.

〔The invention's effect〕

As described in detail above, according to the present invention, it is possible to provide a method for driving a semiconductor optical memory, which can transfer optical information to an arbitrary memory device and can be applied to an optical computer, optical switching, an optical / electrical integrated circuit, and the like. Have.

[Brief description of drawings]

FIG. 1 is a schematic sectional view of a semiconductor optical memory for explaining the operation of the present invention, FIG. 2 is a plan view of FIG. 1, and FIGS. 3 (a) to 3 (d) are semiconductors shown in FIG. Diagram showing applied voltage for driving each optical memory element of the optical memory,
FIG. 4 is a schematic sectional view of a semiconductor optical memory for explaining the prior art, and FIG. 5 is a schematic view when the device of FIG. 4 is used in a horizontal and vertical direction. 1 ... n-GaAs substrate, 2 ... n-Al _0.4 Ga _0.6 As layer 3,6 ... p-GaAs layer, 4 ... n-GaAs layer 5 ... p-Al _0.4 Ga _0.6 As layer, 7 ... … P-type electrode 8 …… n-type electrode, 9,10,11,12,13,18,19 …… Optical information 14,15,16,17 …… Optical memory device, 20 …… A-1 device 21… … A-2 element, 22 …… B-1 element 23 …… B-2 element, 30 …… Write pulse (1) 31,35,38,43 …… Bias, 32 …… Read pulse (1) 33… … Read pulse (2), 34 …… Write pulse (2) 36 …… Read pulse (3), 37 …… Write pulse (3) 39 …… Read pulse (4), 40 …… Reset pulse (1) 41 ...... Reset pulse (2), 42 ...... Reset pulse (3)

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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. A method for driving a semiconductor optical memory in which a plurality of optical memory elements are formed on at least a cathode layer or a layer other than an anode layer on the same substrate, and each light emitting layer and light receiving layer are formed on substantially the same plane. 2. A method for driving a semiconductor optical memory according to, wherein a write pulse is applied to an adjacent optical memory element in synchronization with a read pulse of the optical memory element having optical information.