JPS586314B2 - Densousenroshinpukuhenchiyousoshi - Google Patents

Description

Detailed Description of the Invention The present invention provides a transmission line amplitude modulation element that amplitude modulates microwaves and millimeter waves using light or electron beam signals by utilizing the properties of transmission lines that utilize the effect of blocking electrodes provided on semiconductors. It is related to.

Conventionally, in order to modulate microwaves and millimeter waves using optical or electron beam signals, a hole is made in the center of a rectangular waveguide 1 as shown in FIG. ) 2 is inserted, and a hole is also used in the side surface of the rectangular waveguide 1 for irradiating the semiconductor 2 with light or an electron beam.

Both ends of the semiconductor 2 are made of ohmic electrodes, and a DC voltage is applied between terminals 4 and 5.

The light or electron beam P entering through the hole 3 is irradiated onto the semiconductor 2, and as a result, an excessive number of pairs of electrons and holes proportional to their intensity are injected into the inside of the semiconductor 2. As a result, the resistance between the terminals of the semiconductor 2 is will decrease.

Therefore, the amount of microwaves that can pass through the semiconductor 2 decreases as the intensity of the externally applied light or electron beam increases.

In this way, the semiconductor and microwave will change according to changes in the strength of the external signal.

The response time of a modulator based on such a principle to an external signal depends on the lifetime of the carrier, so the minimum response time when using Si or the like is about several tens of microseconds.

In addition, since a rectangular waveguide is used, the dimensions are large.
When attempting to modulate with an electron beam, there was a drawback in that the waveguide for that part also had to be housed in a vacuum container.

The present invention was made in view of these points, and includes a resistive semiconductor layer having a blocking electrode formed on a conductive layer, and a bias voltage applied to create a depletion layer in the resistive semiconductor. This is a transmission line amplitude modulation element that modulates the amplitude of microwaves or millimeter waves by irradiating the transmission line piece with a light or electron beam signal.

Hereinafter, the present invention will be explained with reference to the accompanying drawings, in which the resistive semiconductor layer has an intermediate impurity concentration n0 (no.
1013 cm-3), and the conductor layer is an n-type semiconductor (male-type semiconductor) made by adding a large amount of shallow energy level impurities.

FIG. 2 shows an embodiment of an element that modulates the amplitude of microwaves or millimeter waves using optical or electron beam signals according to the present invention.

In the figure, 6 is an n+ type semiconductor layer, 7 is an n type semiconductor layer,
8 is a blocking electrode of a transmission line for microwave input, 9
is the blocking electrode of the bias transmission line, 10 is the blocking electrode of the amplitude modulated wave output transmission line, 11 and 1
2 is a bias terminal, 13 is a blocking electrode of the amplitude modulation section, and 17 and 18 are dielectric materials, which have the function of disabling direct current between the electrodes.

In addition, the thickness h of the n-type semiconductor layer 7 is selected so that it is completely filled with a depletion layer when a bias voltage is applied, and generally h = 2 to 200 μm, although it depends on the magnitude of the bias voltage.
There are several possible degrees.

A reverse bias voltage is applied to the terminals 11 and 12 of the blocking electrodes 8 and 10 (the bias terminals 11 and 12 may be formed of transmission lines), and the n-type semiconductor layer 7 in these parts is
When filled with a depletion layer, the depletion layer acts as a dielectric for microwaves, so the blocking electrode 8 and the n+ type semiconductor layer 6 and the blocking electrode 10 and the n+ type semiconductor layer 6 form a transmission line. become.

The width W of this transmission line is determined by determining the characteristic impedance value and thickness h for microwaves propagating through this line.

ε1 is the dielectric constant, ε1=13 for GaAs and ε=12 for Si, so if Zo is 50Ω, h
/w■0.5.

Therefore, if the thickness h is 2 μm, the width W is 4 μm.

In addition, the portion 14 of the bias transmission line having the electrode 9 is thin, and this forms an inductor that prevents the microwave propagating through the main line from leaking to the bias power source through the bias transmission line. This is to make it happen.

The blocking electrode 13 of the amplitude modulation section is connected to the transmission line having the electrode 8, the transmission line having the electrode 10, and the capacitor 1.
5 and 16.

In addition, the blocking electrode 13 of the amplitude modulation section is sufficiently thin compared to other blocking electrodes, and its thickness is not clearly shown in the drawings, but it is generally several tens to several hundreds of Å.
It is made to be semitransparent to light or electron beams to some extent.

A reverse bias voltage is applied to the electrodes 8, 9, and 10, the n-type semiconductor layer 7 is completely filled with a depletion layer, and a microwave voltage is applied to the transmission line having the electrode 8.

If the electrode 13 is not irradiated with light or electron beam, the microwave propagating through the electrode 8 can directly pass through the amplitude modulation section and reach the output transmission line having the electrode 10.

The injection process for light and electron beams is somewhat different.

First, modulation by an electron beam will be explained. Figure 3 is the second
It is a cross-sectional view of the amplitude modulation part in a figure.

A reverse bias voltage to the extent that the electric field inside the depletion layer can be considered to be almost uniform is applied to the electrode 13 of the modulation section in advance.

The electron beam is directed to the electrode 1 as shown by the dashed line with an arrow in the figure.
3, electron-hole pairs (carriers) are created on the surface of the n-type semiconductor layer 7 (FIG. 3a).

Since a negative voltage is applied to the n-type semiconductor layer 7, the holes are immediately absorbed by the electrode 13, but electrons proceed toward the n+-type semiconductor layer 6.

Assuming that an electron beam of a constant intensity is irradiated, the number of electrons excited one after another by subsequent electron beams will also be n.
Since it progresses toward the +-type semiconductor layer 6, it reaches the state shown in FIG. 3C through the process shown in FIG. 3B.

The saturated electron velocity is 107c for n-type GaAs, Si, etc.
m/sec, so in a device with a thickness h of 3 μm, the injected electrons will last about 30 p seconds, and as mentioned above, if the thickness h is 2 μm
Of course, if it is m, it will reach the n+ type semiconductor layer 6 proportionally in about 20 p seconds.

Assuming that the electron beam flow changes sufficiently slowly compared to the time it takes for the electron beam to travel through the depletion layer, that is, the electron travel time, then the injected electrons initially reach the n+ type semiconductor layer 6.
After reaching , the electron density inside the depletion layer is considered to be uniform, and it can be considered that the electron density inside the depletion layer changes uniformly in response to changes in the intensity of the electron beam.

In FIG. 2, a microwave frequency carrier wave applied to a transmission line having electrodes 8 is coupled with an electron flow in an amplitude modulation section and is attenuated.

Therefore, a microwave modulated by the beam is obtained on the transmission line having the electrode 10.

When electron-hole pairs (carriers) are injected into an n-type semiconductor layer by an optical signal, the manner in which they are injected differs depending on the wavelength of the light.

Generally, a large amount of carriers are injected into a portion close to the blocking electrode, and the injection rate decreases as it moves away from the n-type semiconductor layer.

Therefore, even after reaching a steady state, the distribution of electrons and holes within the depletion layer is not uniform.

However, these carriers still have a strong effect on microwaves, so microwaves can be modulated using exactly the same principle as in the case of electron beams.

Incidentally, the degree of modulation of the amplitude modulation element according to the present invention is influenced by the transmission intelligibility of the transmission line of the amplitude modulation section.

If the amount of electrons injected by the electron beam or light is δn, and the amount of attenuation per unit length is α, then the relationship between α and δn is given by the following equation.

FIG. 4 shows the results of determining the relationship between the amount of injected electrons and the amount of attenuation based on equation (1).

For example, if the length of the amplitude modulation section is 1000 μm, δ
The 100 GHz microwave output modulated by n = 1014 cm-3 is approximately 1/3 of the carrier wave input, and δn =
At 1015 cm-3, it is approximately 2/300.

The response characteristics of an electron beam or an optical signal are influenced not only by the traveling time of the injected electrons and the layer thickness h mentioned above, but also by the lengthwise passage time of the microwave through the modulation section. If the length l of the amplitude modulation part is kept to about 1000 μm, the transit time will be about 10 p seconds, so the transit time of the injected electrons in the thickness direction is longer than the previous example, h = 2,3 μm. Then become dominant.

Rather, the excellent response characteristics can be prevented from being limited by length.

In accordance with the above explanation, examples of numerical values that satisfy each condition will be described based on manufacturing examples.

Considering a microwave carrier wave of 100 GHz, an impurity concentration n is formed by an epitaxial method on the n+ silicon layer 6, which has a sufficiently large impurity concentration of 1019.

The device shown in FIG. 2 was manufactured using a Si single crystal on which an n-layer 7 of =10<14>cm<-3> was grown by a normal microfabrication technique.

As described above, line thickness h = 2 μm, line width ω = 4
μm, and amplitude modulation length l = 1000 μm.

In addition, the length li of the inductor forming portion 14 is selected to be 1/4 wavelength, so in this case it is 250 μm, and the width wb of the bias electrode line portion 9 is selected to be 20 μm, which is five times the main line width w = 4 μm. This prevents microwave leakage.

Incidentally, the dielectrics 17 and 18 are formed by growing thin films of SiO2 to a thickness t=0.2 μm using a normal sputtering technique.

In the description of the above embodiments, a nm semiconductor layer has been used as the conductor layer, but an ohmic electrode may also be used, and the resistive semiconductor layer is not limited to n-type, but may also be p-type.
When using a type semiconductor, this is possible by reversing the polarity of the bias voltage.

As described in detail above, the present invention includes a resistive semiconductor layer having a blocking electrode formed on a conductive layer or a metal layer, and a bias voltage applied to create a depletion layer in the resistive semiconductor. An element that amplitude modulates a carrier wave such as a microwave or millimeter wave by applying an optical or electron beam signal using a transmission line piece consisting of a It has such features.

(1) The modulation frequency of conventional devices that modulate microwaves, etc. with light or electron beam signals is determined by the lifetime of minority carriers, and is at most several 100 KHz.
The device of the present invention can amplitude-modulate microwaves, millimeter waves, etc. with light or electron beam signals varying from low frequencies to microwaves.

(2) The device of the present invention occupies a semiconductor area of less than 10 −4 cm 2 and can be extremely small compared to conventional devices of this type.

(3) As mentioned above, the response speed can be extremely increased from the conventional μ second order to the p second order.

As described above, since the present invention has excellent features, it can be used for transmitting television image signals, for transmitting television image signals, for transmitting multiplexed signal optical communications, and as a double modulator (optical/electrical quantity converter) in place of conventional devices of this type. ), it can be applied to some devices such as measurement control.

[Brief explanation of drawings]

Fig. 1 is an explanatory diagram of a conventional amplitude modulation device, Fig. 2 is an embodiment of an amplitude modulation element according to the present invention, Fig. 3 is a diagram of the operating principle of the element of the present invention, and Fig. 4 is an electron injection amount versus attenuation amount. This is a relationship curve diagram. 1... Rectangular waveguide, 2... Semiconductor, 3... Hole, 4, 5,
11, 12...terminal, 6...n+ type semiconductor 1, 7...n
type semiconductor layer, 7'... Depletion layer, 8, 9, 10, 13...
Blocking electrode, 15, 16... Capacitor, 17,
18... Dielectric, 19, 20, 21, 22, 23... Amplitude modulation section, 24... Transmission line.

Claims (1)

[Scope of Claims] 1. A conductor layer, a resistive semiconductor formed on the conductor layer, and at least one blocking electrode semitransparent to an electron beam provided on the resistive semiconductor, and the blocking electrode A transmission line piece consisting of a bias voltage applying means for creating a depletion layer which becomes an electromagnetic wave propagation medium in the resistive semiconductor due to the effect of It has a modulated wave output mechanism, and amplitude modulates the carrier wave from the carrier wave input end by irradiating the blocking electrode portion with an electron beam, and extracts the modulated wave from the modulated wave output end. Transmission line amplitude modulation element. 2. A conductive layer, a resistive semiconductor formed on the conductive layer, and a blocking electrode that is semi-transparent to at least one light beam on the resistive semiconductor, and the effect of the blocking electrode makes the resistive A transmission line piece comprising a bias voltage applying means for creating a depletion layer serving as an electromagnetic wave propagation medium in a semiconductor, at least one carrier wave input mechanism made of the transmission line piece, and at least one modulated wave output mechanism. Transmission line amplitude modulation, characterized in that the carrier wave from the carrier wave input end is amplitude modulated by irradiating the blocking electrode portion with a light beam, and the modulated wave is extracted from the modulated wave output end. element.