CN103034014A - THz (Terahertz) wave modulator - Google Patents

Abstract

The invention discloses a terahertz wave modulator, which comprises a terahertz wave permeable semiconductor substrate (1), a metal oxide semiconductor field effect transistor array (2) distributed on the semiconductor substrate (1) according to a certain period ), the metamaterial resonant unit array (3), the first metal plate (4) and the second metal plate (5) prepared on the metal oxide semiconductor field effect transistor array (2); the first metal plate (4) and The source and the drain of the metal oxide semiconductor field effect transistor are connected; the second metal plate (5) is connected with the gate of the metal oxide semiconductor field effect transistor. The working voltage of the metal oxide semiconductor field effect transistor in the present invention is very low, so that the terahertz wave modulator prepared with it can work at low voltage. The switching time of the metal oxide semiconductor field effect transistor is extremely short, on the order of 10-100 ns, so that the modulation rate of the terahertz wave modulator prepared with it can be greater than 10 MHz.

Description

A terahertz wave modulator

technical field

The invention relates to a modulator, in particular to a terahertz wave modulator, and belongs to the fields of terahertz communication, detection and imaging.

Background technique

Terahertz (THz) waves refer to electromagnetic waves from 0.1THz to 10THz, with a wavelength in the range of 0.03mm-3mm, between microwave and infrared. Compared with electromagnetic waves in other bands, terahertz waves have the characteristics of small photon energy and strong penetrating power, which has brought profound impacts on the fields of communication, military, medicine, security inspection and so on. Among them, a high-speed terahertz wave modulator with a modulation rate greater than 10 MHz is one of the essential devices in a terahertz communication system, but the current modulation rate of a terahertz wave modulator is mainly limited by the performance of the substrate material and the device structure.

Among the terahertz wave modulators reported in recent years, there is a method of modulating terahertz waves by using semiconductor bulk materials. Based on ultra-high resistivity silicon wafers, Li Jiusheng from China Jiliang Institute used 808nm laser irradiation to generate photogenerated carriers, thereby changing the refractive index of silicon wafers to modulate terahertz waves. Due to the long recombination lifetime of carriers in ultra-high resistivity silicon wafers, the modulation rate is only 0.2Kbps. Gallium arsenide has a short lifetime of carriers and can be used as a substrate for the preparation of high-speed terahertz modulators. L. Fekete et al. from the Czech Republic adopted a method of embedding a defect layer of gallium arsenide in an alternately stacked periodic structure of silicon oxide and magnesium oxide to form a one-dimensional photonic crystal. The change of the concentration of the carrier modulates the transmission characteristics of the photonic crystal, so as to realize the purpose of high-speed modulation of the terahertz wave. However, due to the short recombination life of carriers in GaAs, the response time is about 130 ps, so although the modulation rate of terahertz waves can reach GHz in theory, in order to obtain higher photogenerated carriers Concentration and large modulation depth, the luminous flux of the 810nm modulated laser needs to reach a very high level of 0.8μJ/cm ² , and the corresponding continuous wave output laser power needs to reach more than 10 ⁵ W, which makes this modulator in practice application is severely limited.

Referring to Figure 1, some researchers have recently proposed a high-speed terahertz wave modulator based on high electron mobility transistors and metamaterial structures, but the layer structure of this kind of high electron mobility transistors is more complex than that of metal oxide semiconductor field effect transistors. The preparation process is long, the cost is high, and its parasitic capacitance is large, which limits the modulation rate of the modulator.

Contents of the invention

In view of the deficiencies in the prior art, the purpose of the present invention is to provide a terahertz wave modulator with low manufacturing cost, which can work at low voltage and whose modulation rate is greater than 10 MHz.

In order to achieve the above object, the present invention is achieved through the following technical solutions:

The terahertz modulator provided by the present invention includes a terahertz wave-permeable semiconductor substrate, a metal oxide semiconductor field effect transistor array distributed in a certain period on the semiconductor substrate, and a metal oxide semiconductor field effect transistor array prepared on the metal oxide semiconductor field effect transistor array. The metamaterial resonant unit array, the first metal plate and the second metal plate; the first metal plate is connected to the source and drain of the metal oxide semiconductor field effect transistor; the second metal plate is connected to the metal oxide semiconductor field effect transistor connected to the grid.

The above-mentioned semiconductor substrate adopts a P-type silicon substrate.

The switching time of the metal oxide semiconductor field effect transistor is 10-100 ns.

The preparation material of the metamaterial resonant unit in the above metamaterial resonant unit array is gold.

The thickness of the metamaterial resonance unit is 200nm-2000nm.

The beneficial effects of the present invention are as follows:

Because the working voltage of metal oxide semiconductor field effect transistor is very low, the terahertz wave modulator prepared by it can work at low voltage, and the structure of metal oxide semiconductor field effect transistor is simple, the preparation cost is low, the process is mature, and it is convenient Miniaturization and integration of devices; due to the extremely short switching time of metal oxide semiconductor field effect transistors (10-100ns), it can be made into a high-speed terahertz wave modulator with a modulation rate greater than 10MHz.

Description of drawings

Figure 1 is a terahertz wave modulator based on high electron mobility transistors and metamaterials prepared in the prior art (where the numbers mean: semiconductor substrate 11, high electron mobility transistor array 22, metamaterial resonant unit array 33, The first metal plate 44 connected to the source and drain of the high electron mobility transistor, and the second metal plate 55 connected to the gate of the high electron mobility transistor);

Fig. 2 is a schematic structural diagram of a terahertz wave modulator of the present invention;

Fig. 3 is a schematic diagram of a single metamaterial resonant unit on the surface of the terahertz wave modulator of the present invention.

Detailed ways

In order to make the technical means, creative features, goals and effects achieved by the present invention easy to understand, the present invention will be further described below in conjunction with specific embodiments.

2 and 3, the terahertz modulator of the present invention includes a terahertz wave-permeable semiconductor substrate 1, a metal oxide semiconductor field effect transistor array 2 distributed periodically on the semiconductor substrate 1, The metamaterial resonant unit array 3 , the first metal plate 4 and the second metal plate 5 prepared on the oxide semiconductor field effect transistor array 2 . The metal oxide semiconductor field effect transistor array 2 and the metamaterial resonant unit array 3 are connected by metal wires.

Wherein, the first metal plate 4 is connected to the source and drain of the MOSFET; the second metal plate 5 is connected to the gate of the MOSFET.

The semiconductor substrate 1 has a high transmittance to terahertz waves, and a P-type silicon substrate or other semiconductor materials transparent to terahertz waves can be used.

The switching time of the MOSFETs in the MOSFET array 2 is 10-100 ns.

The preparation material of the metamaterial resonance unit in the metamaterial resonance unit array 3 is gold, and its thickness is 200nm˜2000nm.

in working:

When the voltage between the gate, the source and the drain, that is, between the second metal plate 5 and the first metal plate 4 is lower than the threshold voltage of the MOSFET, no channel is formed in the MOSFET. At this time, when the terahertz wave irradiates the metamaterial resonant unit array 3, due to the strong resonance effect of the metamaterial resonant unit, the transmittance of the terahertz wave is very low, which is equivalent to the modulator being in the “off” state;

When the voltage between the gate, the source and the drain, that is, between the second metal plate 5 and the first metal plate 4 is greater than the threshold voltage of the metal oxide semiconductor field effect transistor, a channel can be formed in the metal oxide semiconductor field effect transistor, Electrons can enter the channel from the source, and the resonance effect of the metamaterial resonant unit on the surface of the MOSFET is destroyed. As a result, the transmittance of the terahertz wave is greatly improved, which is equivalent to the modulator being in the "on" state. Since the switching time of MOSFETs is extremely short (10-100 ns), high-speed modulation of the terahertz wave incident on the modulator can be achieved by applying a high-speed modulated voltage signal to the gate.

The working voltage of the metal oxide semiconductor field effect transistor in the present invention is very low, so that the terahertz wave modulator prepared with it can work at low voltage. The switching time of the metal oxide semiconductor field effect transistor is extremely short, on the order of 10-100 ns, so that the modulation rate of the terahertz wave modulator prepared with it can be greater than 10 MHz.

The present invention can also adopt other transistors with high-speed electron mobility and fast response time, such as AlGaN/GaN High Electron Mobility Transistor (AlGaN/GaN HE MT), and metamaterial resonances of different sizes and shapes can also be used unit.

The preparation method of the terahertz wave modulator of the present invention is as follows:

First, grow the epitaxial structure of the metal oxide semiconductor field effect transistor on its semiconductor substrate 1; then use photolithography, etching, evaporation and other processes to prepare the source, drain and gate, and make the metal oxide semiconductor field Effect tube array 2; then metamaterial resonant unit array 3 is evaporated on the surface of the metal oxide semiconductor field effect tube array; finally the first metal plate 4 and the second metal plate 5 are prepared and connected to the metal oxide semiconductor field effect tube array 2 and Metal wires of the metamaterial resonant unit array 3 .

The basic principles, main features and advantages of the present invention have been shown and described above. Those skilled in the industry should understand that the present invention is not limited by the above-mentioned embodiments. What are described in the above-mentioned embodiments and the description only illustrate the principle of the present invention. Without departing from the spirit and scope of the present invention, the present invention will also have Variations and improvements are possible, which fall within the scope of the claimed invention. The protection scope of the present invention is defined by the appended claims and their equivalents.

Claims (5)

1. A terahertz wave modulator, characterized in that it includes a terahertz wave-permeable semiconductor substrate (1), a metal oxide semiconductor field effect transistor array distributed on the semiconductor substrate (1) at a certain period (2), a metamaterial resonant unit array (3), a first metal plate (4) and a second metal plate (5) prepared on the metal oxide semiconductor field effect transistor array (2); The first metal plate (4) is connected to the source and drain of the metal oxide semiconductor field effect transistor; The second metal plate (5) is connected to the gate of the metal oxide semiconductor field effect transistor. 2. The terahertz wave modulator according to claim 1, characterized in that, the semiconductor substrate (1) is a P-type silicon substrate. 3 . The terahertz wave modulator according to claim 1 , wherein the switching time of the MOSFET is 10-100 ns. 4 . 4. The terahertz wave modulator according to claim 1, characterized in that the metamaterial resonant unit in the metamaterial resonant unit array (3) is made of gold. 5 . The terahertz wave modulator according to claim 4 , wherein the thickness of the metamaterial resonant unit is 200nm˜2000nm.

Images