JPH02159736A - High-frequency amplifier element - Google Patents

Abstract

PURPOSE:To prevent a FET from being damaged by a surge voltage or an erroneous operation by a method wherein a capacity is provided between a gate electrode and an input electrode of a field effect transistor while an inductor is provided between the gate electrode and a source electrode. CONSTITUTION:The Schottky junction part of the end of a gate electrode 3 with 2 DEG layers of regions 8 is held by source electrodes 2 and a drain electrode 4 so that a high electron mobility field effect transistor may be formed on the parts of regions 8 on a GaAs substrate 1. A capacitor 6 arranged between an input electrode 5 and the gate electrode 3 is formed of an upper layer metal as an extension of the gate electrode 3 and a lower layer metal as an extension of the input electrode 5 as well as a thin insulating film arranged between these metals. An inductor 7 is composed of a spiral arranged between the extension of the gate electrode 3 and the extension of the source electrode 2. Through these procedures, a FET is hardly damaged by a surge voltage or an erroneous operation.

Description

DETAILED DESCRIPTION OF THE INVENTION <Industrial Application> The present invention relates to a highly reliable high frequency amplification element used for satellite broadcast reception and the like.

<Prior art> GaAs Schottky gate field effect transistor (G
aAs MESFET) and GaAs/GaAlAs heterojunction high-mobility transistor (HEMT) m-v compound semiconductor field effect transistor CFET
) has low noise and high gain in the high frequency band, so it has recently been widely used as the first stage amplification element of high frequency receivers for receiving satellite broadcasting.

In order to improve the noise performance and gain performance of GaAs MESFETs and HEMTs, efforts are being made to shorten the gate length and gate width, and currently the gate length is 0.2.
In a HEMT with a firn gate width of 100 μm,
High performance with a noise figure of 0.6 dB and a gain of 12 dB has been achieved at a frequency of L2 GHz.

Furthermore, in the past, the optimal value of the gate bias voltage during FET amplification operation differed depending on the device, but recently, due to improvements in the design and fabrication technology of the FET active layer, even when the gate bias is OV, High-performance amplification characteristics can now be obtained.

On the other hand, another method for improving the noise performance of a high-frequency receiver is to reduce the loss that occurs between the antenna, which is the entrance of the high-frequency signal, and the first-stage amplification element (FET). In order to reduce the loss, it is effective to arrange the amplifying element (FET) as close to the antenna as possible and to make the length of the transmission line between the antenna and the amplifying element extremely short.

<Problem to be Solved by the Invention> By the way, another problem arises in the FET whose noise performance and gain performance are maximized in this way. In other words, in this type of FET, the gate length is extremely shortened,
The gate width is also shortened, and it is also extremely susceptible to damage if a voltage higher than the rated voltage is applied to the gate electrode (input electrode) due to erroneous operation or the like.

This type of FET can be mounted in a package,
Alternatively, it can be assembled into a high frequency circuit board as a pair of chips.
However, surge voltage is likely to occur during this assembly process and may damage the FET. Furthermore, before incorporating the FET into a cylindrical frequency circuit board, the high frequency characteristics or DC characteristics are measured, but even during this measurement, due to incorrect operation etc.
A voltage higher than the rated voltage may be applied to the gate electrode of the ET, making it extremely susceptible to damage.

Therefore, if it is possible to prevent damage to the FET having the above-mentioned configuration, which is extremely favorable in terms of noise characteristics and gain characteristics, by a simple method, it will provide a practically extremely effective high-frequency amplification element.

The present invention was devised in view of the above points, and is resistant to damage caused by surge voltage instantaneously applied to the input electrode, and extremely resistant to damage caused by erroneous operation during characteristic measurement. The object of the present invention is to provide a high-frequency amplification element with excellent low noise and high gain properties.

<Means for Solving the Problems> In order to achieve the above object, a high frequency amplification element according to the present invention includes a field effect transistor in which a source electrode, a gate electrode, and a drain electrode are provided on a semiconductor layer, and an external input signal. The above field effect transistor, comprising an input electrode for introduction, a capacitor provided between the above gate electrode and the input electrode, and an inductor provided between the above gate electrode and the source electrode, The input terminal, the capacitor, and the inductor are configured to be monolithic or housed in one housing, and when implementing the present invention, the absolute value of the impedance of the capacitor described above is set to amplify the high frequency amplification element of the present invention. It is preferable to set the resistance to 1000Ω or more in the operating frequency band.

<Function> The above capacitor prevents surge voltages generated at the input electrodes for some reason or voltages exceeding the rated voltage due to erroneous operation from being transmitted to the gate electrodes, and at the same time, it effectively controls the high-frequency signal voltage input to the input electrodes. In addition, since the inductor always keeps the gate electrode and the source electrode at the same potential, the field effect transistor described above is not affected by abnormal voltage, and a high frequency amplification element that is extremely difficult to damage can be obtained. .

<Examples> The present invention will be explained in detail below using illustrated examples.

FIG. 1 is a configuration diagram showing one embodiment of the high frequency amplification element of the present invention, in which 1 is a GaAs substrate, 2 is a source electrode, 3 is a gate electrode, 4 is a drain electrode, and 5 is an externally A capacitor 6 is disposed between the input electrode 5 and the gate electrode 3, and a capacitor 7 is disposed between the gate electrode 3 and the source electrode 2. It is an inductor.

To be more specific, the region 8 on the GaAs substrate 1
In the part, a non-doped GaAs epitaxial layer,
A Si-doped GaAlAs epitaxial layer is formed, and a two-dimensional electronic layer (ZDEG layer) is formed.

The source electrode 2 and the drain electrode 4 are in good ohmic contact with this ZDEG layer. The tip portion of the gate electrode 3 and the 2DEG layer in the region 8 are electrically coupled through a Schottky junction. This Schottky junction is arranged so as to be sandwiched between the source electrode 2 and the drain electrode 4, so a high electron mobility field effect transistor (HEMT) is formed in the region 8 on the GaAs substrate 1. This means that it has been done. In the HEMT of this example, in order to improve the noise performance and gain performance in the high frequency band to the maximum, the total source-drain distance was set to 2 μm, and the gate length was set to 0.2 μm.
, the gate width was 100 μm.

The saturated drain current (IDSS) of this HEMT is 5mA
Furthermore, when this HEMT is operated at high frequency, sufficiently good amplification characteristics and noise characteristics can be obtained even if the gate bias voltage is OV (that is, the source and gate are at the same potential). The channel layer is designed like this.

A capacitor 6 disposed between the input electrode 5 and the gate electrode 3 has an upper metal layer extending from the gate electrode 3, a lower metal layer using the extended portion of the input electrode 5, and a thin insulating film (for example, SiNx) between them. membrane). The capacitance value of this capacitor is a small impedance that can be ignored in the frequency band to be amplified by this amplification element, but it has a high probability of being at low frequencies (IM, Hz or less) such as surge voltage. The impedance is selected to have an extremely high impedance against noise.

In order to carry out amplification operation in the 12 GHz band in the amplification element of the example, the absolute value of the impedance of this capacitor was selected to be 5 pF so that it would be sufficiently small in the 12 GHz band.

The absolute value of the impedance of a 5pF capacitor at 12GHz is calculated to be approximately 2.6Ω, so it can be ignored for the most part, but for example, for an IMHz surge voltage, 32Ω
acts as a high impedance of Ω.

The inductor 7 is an extension of the gate electrode 3 and the source electrode 2.
It consists of a spiral placed between the extension part of the The inductance value of this inductor 7 is
The impedance is selected to be sufficiently large in the frequency band to be amplified by this amplifying element. In the example, the inductance of the spiral inductor was set to i20OnH so as to have a sufficiently high impedance for signals in the 12 GHz band. The absolute value of the impedance of a 200 nH inductor is about 15 Ω in the 12 GHz band, so it can be considered almost infinite.

Now, the high-frequency amplification element of this embodiment configured as described above has high gain performance like a normal FE'T or HEMT.
It will be explained below that it has excellent low noise characteristics and is extremely resistant to damage due to surge voltage or incorrect operation.

In order to operate this amplification element, the input electrode 5, source electrode 2, and drain electrode 4 are connected to an external circuit by bonding wires or the like. Further, the measuring device and each electrode may be connected by probe needles for the purpose of element selection or the like.

First, the source electrode 2 is grounded, and the drain electrode 4 is connected to +3V.
Apply a DC voltage of approximately Next, when a high frequency signal is introduced into the input electrode 5, the signal is transmitted from the input electrode 5 to the gate electrode 3 with almost no loss, since the impedance of the capacitor 6 is so low that it can be ignored with respect to the high frequency signal. The gate electrode 3 is connected to the same potential as the half-circle electrode 2 by an inductor 7. That is, the state of gate bias OV in a normal FET is always realized. Since the inductor 7 has a sufficiently high impedance in the frequency band to be amplified by the present amplification element, the high frequency signal introduced into the gate electrode 3 is hardly affected by the inductor 7 and is transferred to the transistor active layer (region 8). be guided. Therefore, the input signal of this amplification element is a normal FET.
It is amplified by the same amplification effect and output from the drain electrode 4, and moreover, the FET (
Here, since the HEMT) has high performance, the performance of this amplification element is also excellent.

In addition, in the amplifying element of this embodiment configured as described above, even if a voltage higher than the rated voltage is introduced into the input electrode 5 due to a surge voltage or an erroneous operation, the capacitor 6 will not have a high impedance, and the surge will occur. Since the inductor 7 always keeps the gate electrode 3 and the source electrode 2 at the same potential at low frequencies, the transistor active layer (region 8) is almost free from surge voltage etc. This amplification element is extremely difficult to damage without being exposed to the effects of

FIG. 2 is a configuration diagram showing another embodiment.

The difference between this embodiment in FIG. 2 and the first embodiment is that the input electrode 5, capacitor 6, and inductor 7 are not monolithically formed with a field effect transistor.

In FIG. 2, 1 is a GaAs semiconductor substrate, and an FET chip with a source electrode 2, a gate electrode 3, and a drain electrode 4 formed on the GaAs substrate 1 is housed inside a high-frequency package (casing) 9. There is. An input electrode 5 provided within a package 9 is connected to a gate electrode 3 on the FET chip via a chip capacitor 6 by wire bonding. Further, the electrode on the gate electrode 3 side of the chip capacitor 6 is bonded to a ground electrode 10 in the package 9 via the chip inductor 7. The source electrode 2 of the FET is directly bonded to a ground electrode 10.11 in the package 9. The drain electrode 4 is directly bonded to the output electrode 12 inside the package 9. For the same reason as in the first embodiment, a high frequency amplification element with such a configuration also uses a normal FE.
It is possible to obtain a high frequency amplification element that is completely comparable to T and has excellent high gain and low noise properties, and is extremely hard to break.

In addition, in the frequency band in which this high-frequency amplification element operates, such as the one used in this embodiment, the absolute value of the impedance of the capacitor 6 can be considered to be an almost negligible value, and the absolute value of the impedance of the inductor 7 can be considered to be almost infinite. However, if the values of the capacitor 6 and inductor 7 are limited due to restrictions such as element dimensions, the absolute value of the impedance of the capacitor 6 must not exceed 10Ω, and the impedance of the inductor 7 A similar effect can be expected if the absolute value of is not less than 1000Ω. In addition, since the capacitor 6 acts as a bypass filter, if noise such as surge voltage occurs frequently at a frequency relatively close to the frequency band in which this amplification element is operated, the absolute value of the impedance of the capacitor 6 should be Must be set to a finite value.

<Effects of the Invention> As described above, according to the present invention, it is possible to overcome, with a simple configuration, the weakness of FETs, which are excellent in high gain and low noise at high frequencies, that they are extremely susceptible to damage due to surge voltage or erroneous operation. This makes it possible to obtain a high-performance and highly reliable high-frequency amplification element.

[Brief explanation of the drawing]

FIG. 1 is a block diagram showing one embodiment of the high frequency amplification element of the present invention, and FIG. 2 is a block diagram showing another embodiment of the present invention. 1...GaAs substrate 2...Source electrode 3...
Gate electrode 4...Drain electrode 5...Manual electrode, 6...Capacitor 7...Inductor
8... Transistor active area 9... Housing Figure 1

Claims (1)

[Claims] 1. A field effect transistor having a source electrode, a gate electrode, and a drain electrode provided on a semiconductor layer, an input electrode for introducing a signal from the outside, and between the gate electrode and the input electrode. and an inductor provided between the gate electrode and the source electrode, and the field effect transistor, the input electrode, the capacitor, and the inductor are configured to be monolithic or housed in one housing. A high frequency amplification element characterized by: