JPS63147382A - Resonance tunnel type negative resistance element - Google Patents

Abstract

PURPOSE:To obtain a negative resistance element capable of an adequate voltage margin by a method wherein a quantum well is of a multiple quantum well structure. CONSTITUTION:On a semiconductor substrate 11 of the first conductivity type, a first semiconductor layer 12 of the first conductivity type, quantum well 13 consisting of a second semiconductor layer to serve as a barrier layer and laminate of third semiconductor layers, and fourth semiconductor layer 14 of the second conductivity type are built into a mesa, in that order. The quantum well 13 in a resonance tunnel type negative resistance element thus constructed is of a multiple quantum well structure. For example, on an n-type InP substrate 11, provided with an ohmic electrode 17 on its rear side, and a quantum well 13, which is a laminate of an undoped InAlAs and InGaAs respectively serving as a barrier layer and well layer, are formed, with an n-type InAlAs layer 12 between. On the quantum well 13 of a multiple quantum well structure, further, a p-type InGaAs layer 15 for ohmic contact and contact electrode 10 are built, through the intermediary of a p-type InAlAs layer 14. All the layers are subjected to a mesa-etching process.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a resonant tunnel negative resistance element having a large negative resistance voltage range.

[Prior Art] Conventionally, as a resonant tunnel type negative resistance element using a quantum well structure, one having a structure as shown in FIG. 4 has been used. In the figure, 1 is an n-type GaAs substrate with an ohmic electrode 6 formed on the back side.

On the main surface of the G&Al substrate 1, there is a single quantum well structure consisting of a laminated structure of an n-type GaAs layer 2, an undoped GaAtA layer 3 serving as a barrier, and an and-7' GaAs layer serving as a well layer, and an n-type GaAs layer. 5 is formed by epitaxial growth. An ohmic electrode 7 is formed on the n-type GaAs layer 5. After the formation of the ohmic electrode 7, the single quantum well structure portion and the n-type GaAs layer 5 portion are subjected to a circular mesa etch process. Considering this three-dimensional structure, negative resistance elements do not require waveguiding for optical input and output compared to other devices using quantum well structures such as Rade optical modulators, so they can be applied in the form of mesa shapes. The difference is that it uses a circular shape with excellent uniformity of the electric field. Such a negative resistance element has a problem in that conventionally, only those with a single quantum well as shown in FIG. 4 have been considered. This problem will be explained below.

[Problems to be Solved by the Invention] The band structure of the conductor of the conventional resonant tunneling negative resistance element configured as shown in FIG. 4 is the same as shown in FIG. (4) in the same figure shows the band structure when the bias voltage OV is applied, and (B) in the same figure shows the band structure when the bias voltage is applied. Further, the current-voltage characteristics of this element are as shown in FIG. The current in Figure 5 (B) reaches a maximum near the voltage at which the level in the single quantum well resonates with the bottom of the conduction band of the n-type GaAs layer outside the well, and when the voltage is further applied, negative resistance appears. , then the contribution of hot carriers increases and the current increases again. A practical problem with this characteristic is that the voltage difference V between the two techniques in the characteristic shown in FIG. 6 is usually very small, 10 QmV or less. This is because the quantum well is single, so the negative resistance is 1
Only one quantum well can be obtained, and the voltage difference is approximately determined by the voltage applied to the single quantum well. Therefore, the small voltage difference vfOn is considered to be a drawback essentially resulting from the structure of FIG. 4. The fact that this voltage difference vo is small means that when forming a logic element using this negative resistance element, the voltage margin between HIG)I and LOW in logic becomes small,
It is expected that the variation in characteristics of elements when integrated will exceed the margin, making circuit design extremely difficult.

The present invention has been made in view of these points, and it is an object of the present invention to provide a resonant tunnel type negative resistance element having a characteristic that a sufficient voltage margin can be secured.

[Means for Solving the Problems] The present invention provides a first semiconductor layer having a first conductivity, a second semiconductor layer serving as a barrier layer, and a third semiconductor layer serving as a well layer, on a semiconductor substrate of a first conductivity type. A quantum well structure layer formed of a stacked structure of semiconductor layers, and a fourth quantum well structure layer of a second conductivity type on the quantum well structure layer.
This resonant tunneling negative resistance element has a semiconductor layer in a mesa shape, and is characterized in that a quantum well portion has a multi-quantum well structure.

[Function] According to the resonant tunneling type negative resistance element according to the present invention, the ANDOG multi-quantum well structure is adopted, so that when a voltage is applied, the voltage difference between the two techniques in the current-voltage characteristics is increased. be able to.

Therefore, element characteristics with sufficient voltage margin can be easily obtained.

[Example] An example of the present invention will be described below with reference to the drawings. FIG. 1 is a perspective view showing a schematic configuration of an embodiment of the present invention. In the figure, 11 is an n-type InP substrate with an ohmic electrode 17 provided on the back side.

The ohmic electrode 17 is made of ALLG eN i.

On the InP substrate 11, an n-type InAIA layer 12, all layers 12, and a multi-quantum well structure layer 13 are laminated. The multiple quantum well structure layer 13 is formed using and-f InAtAs and InGaAs for a barrier layer and a well layer, respectively. On the multiple quantum well structure layer 13, a p-type InGaAs layer 15 for ohmic contact and a contact electrode 16 made of AuZnNi are sequentially laminated via a p-type InALklS layer 14t. Note that each layer 1 including the multi-quantum well structure layer 13 under the contact electrode 16
5, 14, and 12 are subjected to mesa etch processing.

The current-voltage characteristics of the resonant tunnel type negative resistance element configured in this way are as shown in FIG. Thus, this element operates based on a band structure as shown in FIG. That is, the applied voltage va is the flat band voltage V,
If it is very low, a band structure as shown in FIG. 3 (4) will be formed and current will hardly flow. As the voltage increases and approaches the flat band voltage V, resonant tunneling occurs and the current increases rapidly (see Figure 3).
When the ratband voltage V is exceeded, an extra voltage is applied to one well of the multiple quantum well, the resonant tunneling condition is broken, the flow rapidly decreases, and negative resistance appears (Fig. 3).
0 reference input When a further voltage is applied, the resonant tunneling condition is satisfied again and the current increases (see Figure 3 (0)).When a further voltage is applied, an extra voltage is applied to another well, causing non-resonant tunneling. The state is broken and the current decreases.In this way, one well enters the resonant tunneling state, and one negative resistance characteristic appears in the characteristic.Therefore, the negative resistance characteristic is small by the number corresponding to the number of wells. When we apply a voltage that appears and all quantum wells cross the resonant tunneling state between different quantum levels,
Due to conduction by hot electrons, the stain current increases monotonically and greatly again.The above effect is clearly seen in the current-voltage characteristics obtained in FIG. This characteristic was first discovered through research by the inventors.

Now, the voltage margin vm in an element with such a structure
' is based on the operating principle described above) As the high electric field region expands and one new quantum well is added to the high electric field region, the voltage increase ΔvI]1 required to exhibit negative resistance characteristics is , it can be seen that when the number of quantum wells is n, it can be approximately estimated by Vn1' and ΔVmXn. Namely.

In this device, a multiple quantum well structure is adopted, and by appropriately selecting the number n of wells, it is possible to set the voltage margin V' to a desired value. Therefore, it is possible to obtain a sufficient value as the voltage Marson v. For example, V at a well number of 40. 'sa6v
A sufficient value has been obtained. As is clear from the above results, the problem of voltage mernon V/ can be solved compared to the conventional one shown in FIG.

In addition, in the example, X nGaAg /I of P1n structure
Although we have explained the case of nAlAs, GaAs/
Other materials such as GaAtAm may also be used, and
It may also have a nin structure. In addition, InA in FIG.
tAsnGaAs layer 12I nA Mug glue layer 14 InG
Of course, it may be replaced with an aAs layer.

[Effects of the Invention] As explained above, according to the resonant tunneling negative resistance element according to the present invention, the negative resistance can be improved so that a large voltage margin can be obtained. element can be realized.

Further, since a large voltage margin can be secured in logic circuit design, it has remarkable effects such as being able to tolerate some variation in the characteristics of elements during integration.

[Brief explanation of the drawing]

FIG. 1 is an explanatory diagram showing a schematic configuration of an embodiment of the present invention,
FIGS. 2 and 6 are explanatory diagrams showing current-voltage characteristics, FIGS. 3 and 5 are explanatory diagrams showing band structures, and FIG. 4 is a schematic diagram of a conventional resonant tunnel type negative resistance element. FIG. 2 is an explanatory diagram showing the configuration. 11...InP substrate, 12-InAAAs layer, 1
3...Multi-quantum well structure layer, 14...p-type InA
tA+s layer, 15... p-type 1nGaAa layer, 16...
- Contact electrode, 17... Ohmic electrode. Applicant's representative Patent attorney Takehiko Suzue Figure 1 Figure 2 (B) e - (C) Figure 3 Figure 4

Claims (3)

[Claims] (1) A first semiconductor substrate of a first conductivity type is placed on a semiconductor substrate of a first conductivity type.
A quantum well structure layer formed of a laminated structure of a semiconductor layer, a second semiconductor layer serving as a barrier layer, and a third semiconductor layer serving as a well layer, and a fourth semiconductor of a second conductivity type on the quantum well structure layer. 1. A resonant tunneling negative resistance element having mesa-shaped layers, characterized in that a quantum well portion has a multi-quantum well structure. (2) The resonant tunnel type negative resistance element according to claim 1, wherein the first conductivity type and the second conductivity type are the same. (3) The resonant tunnel type negative resistance element according to claim 1, wherein the first conductor layer and the fourth conductor layer are formed of the same material.