JP2019057724A - Semiconductor element, semiconductor device and manufacturing method - Google Patents

Abstract

To provide a semiconductor element which allows adjustment of a barrier height φ, and allows a zero bias operation and antenna impedance matching for improvement of detection sensitivity of a high-frequency band RF electric signal; and provide a manufacturing method of the semiconductor element and a semiconductor device equipped with the semiconductor element.SOLUTION: In a semiconductor element according to a present embodiment, a concentration of InGaAs (n-type InGaAs layer 2) is intentionally increased beyond a range where "a change in a barrier height by bias" as mentioned above is prevented to a range to be deeply degenerate thereby to increase an electron Fermi level (E) from a band end of the InGaAs (n-type InGaAs layer 2) toward a band end of an InP (InP depletion layer 3).SELECTED DRAWING: Figure 2

Description

  The present invention relates to a semiconductor element formed by stacking a plurality of semiconductor layers, a manufacturing method thereof, and a semiconductor device including the same.

  In various wireless systems in the millimeter wave to THz frequency band, a nonlinear device is used as a means for detecting a signal included in the RF carrier. A Schottky Barrier Diode (SBD) is one of typical devices, and functions as a mixing device using envelope detection and variable capacitance operation. The background of envelope detection is described here.

Ｖ_Ｔは熱電圧（ｔｈｅｒｍａｌ ｖｏｌｔａｇｅ ＝ ｋＴ／ｑ： ｋはボルツマン常数、Ｔは絶対温度、ｑは電子電荷）であり、室温で２５ｍＶの値となる。
このＩ−Ｖ特性の非線形性を利用することにより、ＲＦ電気信号入力でＳＢＤ端子に誘起される電圧Ｖ_ＲＦにより検波出力（＝平均電流）を発生させることができる。 Current-voltage (I-V) characteristics of the SBD, the saturation current (Saturation Current) as _{I S,} can be expressed by Equation 1.

V _T is a thermal voltage (thermal voltage = kT / q: k is a Boltzmann constant, T is an absolute temperature, and q is an electronic charge), and has a value of 25 mV at room temperature.
By utilizing the nonlinearity of this IV characteristic, a detection output (= average current) can be generated by the voltage V _RF induced at the SBD terminal by the RF electric signal input.

となる。２乗検波の一般論から、シリーズ抵抗Ｒ_Ｓと接合容量Ｃ_ｊを無視し、入力ラインとＲ_Ｄのインピーダンス整合が成立、すなわち、電力の結合が１００％とした場合、入力電力Ｐ_ＲＦに対する検波電流感度は、Ｒ_Ｄが変化しても、ゼロ電圧動作時では１／Ｖ_Ｔ （Ａ／Ｗ）であり、Ｉ_Ｓに無依存の一定値を保つ。
電圧感度（＝オープン出力条件）に関しては、インピーダンス整合状態では、１／Ｉ_Ｓ（Ｖ／Ｗ）であり、Ｉ_Ｓが小さいほど電圧感度は高く、低速の変調信号の場合はこの検波電圧を測定することが多い。通常、ＳＢＤの感度性能として、電圧感度（Ｖ／Ｗ）が用いられる理由である。 FIG. 11 is an equivalent circuit of a diode. FIG. 12 is a diagram schematically showing current-voltage (IV) characteristics of the diode and detection IV characteristics with respect to a high-frequency input. The curve of the detection IV characteristic is an IV characteristic obtained by shifting the IV characteristic when no high frequency signal is input to the negative voltage side, and the operating point P is determined according to the load resistance of the detection output circuit.
When a small signal is input, the real part (= differential resistance value) of the impedance of the SBD is a voltage derivative of the IV characteristic when no high frequency signal is input.

It becomes. From the general theory of square detection, when the series resistance R _S and the junction capacitance C _j are ignored and the impedance matching between the input line and R _D is established, that is, when the power coupling is 100%, the detection for the input power P _{RF is performed} . current sensitivity, even if _{R D} is changed, the time of zero voltage operation is _{1 / V T (a / W} ), maintain a constant value of not depend on _{I S.}
Regarding the voltage sensitivity (= open output condition), in the impedance matching state, it is 1 / I _S (V / W). The smaller the I _S is, the higher the voltage sensitivity is. Often to do. This is why voltage sensitivity (V / W) is usually used as the sensitivity performance of SBD.

On the other hand, when the signal is modulated at high speed, the output current is amplified by using a feedback amplifier having a relatively small input resistance. Therefore, the detection current sensitivity is rather important. As a typical detection operation, let us consider a case where an RF signal is directly input to a zero-voltage operation SBD from a coaxial line or a waveguide line. The characteristic impedance Z0input of these input lines is much smaller than the diode differential resistance (R _D ) as long as the conventional SBD is used (Z0 input << R _D ). That is, the matching condition is not satisfied, and the RF signal to the SBD is almost reflected and the power coupling is insufficient. The detection current sensitivity at the time of impedance mismatching is 2 (Z0input / R _D ) V _T ⁻¹ = 2 (Z0 input × I _S ) V _T ⁻² from the value (1 / V _T ) at the time of impedance matching.
To drop. In such a case, it is necessary to raise I _S , in other words, to raise the output current I _{SBD of the} equation (1) to an appropriate value. This is equivalent to lowering _RD from the relationship of equation (2). For such reason, when the conventional I _S uses like small GaAs-SBD is detection circuit condition given bias ((2) conditions to increase the V has a small R _D in formula) Will be configured. It is possible to improve the matching state by inserting an impedance conversion circuit between the input line and the SBD, but this limits the operating bandwidth, and at the expense of the broadband characteristics of the detection device. End up.

Furthermore, when detecting a weak signal, it is desirable to operate with zero bias in order to suppress the influence of power supply noise. Another advantage is that a bias circuit is not required. In order to obtain a good sensitivity at zero bias state, it is necessary to increase appropriately I _S (1) below. In other words, since V = 0 in Equation 2, R _D = V _T / I _S , and R _D is in a lowered state. However, as long as the SBD is fabricated with the most typical compound semiconductor GaAs, I _S is smaller than the optimum value and R _D is much larger than the effective impedance of the input line.

Particularly important is the case of configuring a broadband receiver that operates in the THz band from several hundred GHz to several THz. The THz receiver is often directly connected to a pure resistance antenna having a constant antenna impedance (Zo), which makes it difficult to incorporate a matching circuit. For example, the net impedance of the resistor antenna about 75Ω low formed on the semiconductor substrate, the impedance matching is difficult to hold, the detection current output at that condition has a tendency to depend on I _S. In the case of such a circuit configuration that is difficult to achieve impedance matching, it is desirable to lower _RD to a value close to Zo in order to ensure coupling efficiency.

ここで、Ａ^＊はリチャードソン常数、ｋはボルツマン常数、Ｔは温度（Ｋ）である。 Here, in order to reduce _RD , it is necessary to increase _IS as is apparent from the equation (2). I _S is a function of the junction area (S _j ) of the SBD and the barrier height (φ _Bn ) of the SBD, as shown in Equation 3.

Here, A ^* is a Richardson constant, k is a Boltzmann constant, and T is a temperature (K).

However, when a wideband receiver is configured, since it is necessary to reduce the junction area _Sj and the junction capacitance (Cj) of the device to ensure the frequency characteristics, φ _Bn is constant (same semiconductor material). inevitably it tends to be difficult to increase the I _S, if any. After all, will be more I _S operation bandwidth required for the receiver rise decreases, far away from the correct state for zero bias operation, there is a problem that characteristics of the zero bias operation is deteriorated.

In order to increase the I _S may be a means to reduce the barrier height phi _Bn of SBD by changing the semiconductor material. For example, there is InGaAsP lattice-matched to InP as a semiconductor material having a barrier height φ _Bn smaller than that of GaAs which is a general semiconductor material. FIG. 10 schematically shows an SBD structure band diagram using InGaAsP. The Schottky barrier metal 36 contacts the low concentration InGaAsP layer 31 to form an SBD structure. The n-type contact layer (33, 34) having a two-layer structure and the contact electrode 35 are connected. Note that the low concentration means “a state where the concentration of the donor or acceptor is low enough to cause little electric charge that causes a large electric field change in the layer when depleted”. That is, the low-concentration InGaAsP layer 31 has a lower donor or acceptor concentration than any other doped layer, and a diode effect can be obtained even when the layer is non-doped.

Among InGaAsPs, the smallest SBD barrier is InGaAs whose InP composition is zero. However, even with InGaAs, the electron barrier φ _Bn is about 0.2 to 0.25 V, and the required S _j decreases as the operating frequency increases. After all, if the number 100GHz or more high-frequency operation of the SBD of interest, can not be reduced as much as phi _Bn obtain desired _{I S.} Univ. In the example of the Darmstadt group, the differential resistance of InGaAs-SBD manufactured for THz frequency band operation is reported to be R _D = 4.7 kΩ at 0 V (for example, see Non-Patent Document 1). _{I S} is calculated from the _{R D} is about 5 .mu.A. It can be seen that this _RD is still much larger than the impedance of a typical pure resistance antenna (about 75Ω).

A diode using a semiconductor heterostructure (heterobarrier diode [HBD: Hetero Barrier Diode]) has been reported (see Non-Patent Document 2) instead of an SBD made of a metal and a semiconductor. Non-Patent Document 2, isotype junctions consisting of n-type InGaAs / n-type InP, have been shown to determine the _{I S} phi _Bn is 200 meV. However, the phi _Bn is equal to phi _Bn of InGaAs-SBD, unlikely the increase in _{I S.}

A diode using a heterostructure of a semi-metal semimetal and a semiconductor has also been reported (see Non-Patent Document 3). The semimetal / semiconductor diode is composed of semimetal ErAs and InAlGaAs [composition is lattice matched to InP under the condition of (In _0.52 Al _0.48 As) _x (In _0.53 Ga _0.47 As) _{1 − x} ], and the condition of x = 0: The ErAs / InGaAs junction is reported as φ _Bn = 150 meV as the minimum barrier height. However, experimentally, the characteristics of the diode having such a small φ _Bn are not good, and the design guideline is not necessarily clarified.

As described above, to improve the performance of the SBD or semiconductor heterostructure diode that performs zero bias operation in the frequency band from millimeter waves to several THz waves, the current sensitivity is increased, and the differential resistance value _RD at the operating point is set at the same time. It needs to be larger than the current device saturation current I _S to an appropriate value. However, it is not possible to optimize the differential resistance value _{R D} and the saturation current _{I S} to InGaAs-SBD still phi _Bn is greater that have been reported, having small fabricated with the intention to increase the _{I S} phi _Bn ErAs The effect is not recognized even in the diode using the / InAlGaAs heterostructure (Non-patent Document 3).

D. Schoeherr et al. "Extremely Broadband Characteristic of a Schottky Diode Based THz Detector", IRMMW-2010, pp. 1-2, 2010. S. R. Forrest and O.M. K. Kim, “An n-In0.53Ga0.47As / n-InPlectifiers”, J. Am. Appl. Phys. Vol. 52, pp. 5838-5842, 1981. E. R. Brown et al. "Advanceds in Schottky Rectifier Performance", IEEE Microwave Magazine, June 2007, pp. 54-59, 2007. N. Kashio et al. "High-Speed and High-Reliability InP-Based HBTs with a Novel Emitter", IEEE Trans. Elec. Dev. Vol. 57, NO. 2, pp. 373-379, 2010.

As described above, the high frequency band, especially in order to increase the performance of the detection device for zero bias operation at THz band, the saturation current I _S of the operating point larger than the current device (= small differential resistance value R _D) to There is a need. However, the conventional SBD cannot realize the small barrier height φ _Bn required for the purpose, and the semiconductor heterostructure diode does not sufficiently reduce φ _{Bn as} compared with the SBD. Design guidelines have not been clarified. That is, the conventional semiconductor detection device cannot reduce the Schottky barrier height φ _Bn , and there is a problem that it is difficult to match the zero bias operation and the antenna impedance for improving the detection sensitivity of the RF electric signal in the high frequency band. .

Therefore, in order to solve the above-mentioned problem, the present invention can adjust the barrier height φ _Bn , improve the detection current sensitivity of the RF electric signal in the high frequency band at the time of zero bias operation, and at the same time can match with the antenna impedance. An object of the present invention is to provide a semiconductor device, a manufacturing method thereof, and a semiconductor device including the same.

In order to achieve the above object, the present invention adjusts the barrier height φ _Bn by adjusting the electron concentration of a semiconductor layer having a higher electron affinity in a semiconductor layer forming a heterojunction in a semiconductor element. It was. In the present specification, the semiconductor element means a hetero barrier diode (HBD).

Specifically, the method for manufacturing a semiconductor device according to the present invention includes an n-type first semiconductor layer, a second semiconductor layer having a lower electron affinity than the first semiconductor layer, an n-type semiconductor layer from the anode side to the cathode side. A method of manufacturing a semiconductor device comprising a stacked diode structure in which a first semiconductor layer and a second semiconductor layer are heterojunction stacked in order of a third semiconductor layer,
The doping amount of the first semiconductor layer is adjusted so as to maximize a detection output current detected by inputting a predetermined high-frequency signal between an anode and a cathode of the semiconductor element.

In the band diagram of FIG. 2, the layer denoted by reference numeral 2 corresponds to the first semiconductor layer, and the Fermi level E _f increases as the n-type doping concentration increases. Here, since the conduction band discontinuity Delta] E _C between the second semiconductor layer is constant, the barrier height energy
[Equation 4]
qφ _Bn = ΔE _C − (E _f −E _C ) (4)
Will change according to. Here, E _f −E _C is a value measured from the conduction band edge of the first semiconductor layer. That is, _φBn can be adjusted by the doping concentration.

In the method for manufacturing a semiconductor device according to the present invention, when a plurality of semiconductor layers including a heterojunction are stacked to form a diode structure, a semiconductor layer (first semiconductor layer having a higher electron affinity) in the heterojunction semiconductor layer is formed. The optimum electron concentration of the semiconductor layer) is acquired in advance. The method for obtaining the optimum electron concentration is an electron concentration at which the detection current becomes maximum when a predetermined RF signal is input. That is, the optimum barrier height φ _Bn is determined using the magnitude of the detection current as an index. Accordingly, the present invention provides a method for manufacturing a semiconductor device that can adjust the barrier height φ _Bn , improve the detection current sensitivity of RF electric signals in a high frequency band during zero bias operation, and at the same time match with the antenna impedance. can do.
It is not known to those skilled in the art that the differential resistance value _RD of the HBD can be adjusted to about the antenna impedance by adjusting the heterobarrier height φ _Bn with the electron concentration of the first semiconductor layer.

The method of manufacturing a semiconductor device according to the present invention includes an n-type first semiconductor layer, a second semiconductor layer having a smaller electron affinity than the first semiconductor layer, and an n-type third semiconductor layer from the anode side to the cathode side. A method of manufacturing a semiconductor device comprising a stacked diode structure in which the first semiconductor layer and the second semiconductor layer are stacked in order, and the second semiconductor layer is a heterojunction,
When the semiconductor element is a detection circuit that inputs and detects a predetermined high-frequency signal between the anode and cathode of the semiconductor element,
When the line impedance on the high-frequency signal input side of the detection circuit or the antenna impedance of the pure resistance and the input impedance of the amplifier connected to the detection output of the detection circuit are given in advance, the current of the detection output is maximized As described above, the doping amount of the first semiconductor layer is adjusted.

  This manufacturing method has a maximum detection current in the line impedance on the high-frequency signal input side when using a semiconductor element in the detection circuit or the antenna impedance of the pure resistance and the input impedance of the amplifier connected to the detection output of the detection circuit. It is preferable to adjust the doping amount of the first semiconductor layer so that

The method of manufacturing a semiconductor device according to the present invention includes stacking an n-type first semiconductor layer, a second semiconductor layer, and an n-type third semiconductor layer in this order from the anode side to the cathode side. A method of manufacturing a semiconductor device comprising a multilayer diode structure in which a layer and the second semiconductor layer are heterojunctions,
The first semiconductor layer is InGaAs,
The second semiconductor layer is InP,
When the area of the heterojunction is S _j (μm ² ), an electron concentration n _e (cm ⁻³ ) of the first semiconductor layer is defined by Formula C1.

The number C1 will be described. First, the number 3, the temperature T is treated as a constant, the relationship of the three parameters of _{I S} and _{S j} and phi _Bn. Here, I _S is uniquely determined by the condition for obtaining the optimum detection current, and when S _j is given according to the frequency to be used, the parameter to be obtained is φ _Bn . Here, looking at Equation 3, log (S _j ) or log [sqr. It is understood that (S _j )] and φ _Bn are in a linear combination relationship.

On the other hand, the number 4, if Kimare heterostructure used by, Delta] E _C so is constant, to decide phi _Bn is nothing but to decide the E _f. Furthermore, experimentally, have been measured previously for several semiconductor materials the relationship between the rise and the carrier concentration n _e of E _f, in the range of constant concentrations following n _e, E _f and n _e is linear I know that there is a relationship. After all, _{n e} and log [sqr. It is understood that (S _j )] has a linear relationship.

Therefore, E when the relationship between the rise and the carrier concentration n _e of _f is known, a semiconductor device having such diode structures described above with actually manufactured optimal n _e from the "maximum value of the detection current" It is not always necessary to ask for. Based on the data of the non-patent document 4 for the case of _InGaAs, the estimated as ^{_{(E f -E C) /q=1.2×10 -20}} × n e, is applied for the case of it InP / InGaAs heterojunction The number C1 is expressed by specific numerical values. The derivation of the number C1 is shown in [Appendix] described later.

Furthermore, the semiconductor element according to the present invention is laminated from the anode side to the cathode side in the order of an n-type first semiconductor layer, a second semiconductor layer, and an n-type third semiconductor layer, A semiconductor element having a multilayer diode structure in which the second semiconductor layer is a heterojunction,
The first semiconductor layer is InGaAs;
The second semiconductor layer is InP;
When the area of the heterojunction is S _j (μm ² ), the electron concentration n _e (cm ⁻³ ) of the first semiconductor layer is represented by Formula C1.

In the semiconductor device and the manufacturing method thereof according to the present invention, when a plurality of semiconductor layers including a heterojunction are stacked and a diode structure is formed, the semiconductor layer having the higher electron affinity in the heterojunction semiconductor layer (first semiconductor layer) (1 semiconductor layer) is determined based on the design value of the junction area of the heterojunction. Therefore, the present invention provides a semiconductor device capable of adjusting the barrier height φ _Bn , improving the detection current sensitivity of the RF electric signal in the high frequency band at the time of zero bias operation, and simultaneously matching with the antenna impedance, and a manufacturing method thereof. Can be provided.

The multilayer diode structure of the semiconductor element according to the present invention is:
An n-type fourth semiconductor layer stacked on the anode side of the first semiconductor layer;
An n-type fifth semiconductor layer stacked on the cathode side of the third semiconductor layer;
Further comprising
The multilayer diode structure is formed on a semi-insulating semiconductor substrate so as to contact the fifth semiconductor layer.

The semiconductor element according to the present invention further comprises an anode electrode and a cathode electrode,
The anode electrode is in contact with the second semiconductor layer opposite to the second semiconductor layer;
The fifth semiconductor layer has an area viewed from the stacking direction larger than the area of the third semiconductor layer,
The cathode electrode is disposed on the third semiconductor layer side of the fifth semiconductor layer and at a position not in contact with the third semiconductor layer.

  The anode electrode of the semiconductor element according to the present invention is characterized in that an area viewed from a stacking direction is larger than an area of the fourth semiconductor layer. Wiring can be facilitated by increasing the area of the anode electrode.

  The first semiconductor layer of the semiconductor element according to the present invention is characterized in that an area viewed from a stacking direction is larger than an area of the second semiconductor layer. The frequency characteristics can be improved by reducing the junction capacitance of the diode.

A semiconductor device according to the present invention includes:
An electrical connection line connecting the electrical high frequency input circuit and the electrical output circuit;
The semiconductor element that connects the cathode side to the electrical connection line, connects the anode side to ground, and outputs a detection signal obtained by detecting an electrical high frequency from the electrical high frequency input circuit to the electrical output circuit;
Is provided.
The semiconductor device includes the semiconductor element described above. Therefore, the present invention provides a semiconductor device capable of adjusting the barrier height φ _Bn , improving the detection current sensitivity of the RF electric signal in the high frequency band at the time of zero bias operation, and simultaneously matching with the antenna impedance, and a manufacturing method thereof. Can be provided.

  In the semiconductor device according to the present invention, the electric high frequency input circuit may be an antenna.

  In the semiconductor device according to the present invention, the electric high-frequency input circuit can be a planar antenna formed on the semi-insulating semiconductor substrate.

The present invention provides a semiconductor device capable of adjusting the barrier height φ _Bn , improving the detection current sensitivity of an RF electric signal in a high frequency band at the time of zero bias operation, and simultaneously matching with the antenna impedance, and a manufacturing method thereof. be able to.

It is a figure explaining the structure of the semiconductor element which concerns on this invention. It is a figure explaining the band diagram of the semiconductor element which concerns on this invention. It is a figure explaining the structure of the semiconductor element which concerns on this invention. It is a figure explaining the structure of the semiconductor element which concerns on this invention. It is a figure explaining the semiconductor device (detection circuit) concerning the present invention. It is a figure explaining the equivalent circuit of the semiconductor device (detection circuit) which concerns on this invention. It is a figure explaining the barrier height and frequency characteristic of the semiconductor element which concerns on this invention. It is a figure explaining the relationship between the electron concentration of the 1st semiconductor layer of the semiconductor element which concerns on this invention, and the detection current which the semiconductor device which concerns on this invention outputs. It is a figure explaining the semiconductor device (detection circuit) concerning the present invention. It is a figure explaining the HBD structure band diagram using InGaAsP. It is a figure explaining the equivalent circuit of a diode. It is the figure which showed typically the current-voltage (IV) characteristic of a diode, and the detection IV characteristic with respect to a high frequency input.

  Embodiments of the present invention will be described with reference to the accompanying drawings. The embodiments described below are examples of the present invention, and the present invention is not limited to the following embodiments. In the present specification and drawings, the same reference numerals denote the same components.

(Embodiment 1)
FIG. 1 is a schematic diagram illustrating the basic configuration of the semiconductor element 301 of the present embodiment. Each semiconductor layer is as follows.
1: High concentration n-type InGaAs contact layer (fourth semiconductor layer)
2: n-type InGaAs layer (first semiconductor layer) with electron concentration adjusted as required
3: Low concentration InP depletion layer (second semiconductor layer)
4: High-concentration n-type InP layer (third semiconductor layer)
5: High concentration n-type InGaAs contact layer (fifth semiconductor layer)
6: Anode electrode 7: Cathode electrode

FIG. 2 is a band diagram of the semiconductor device of this embodiment. The Fermi level (E _F ) and the state of the electron concentration distribution (symbol 10) are shown together. Since the electron affinity of InGaAs is larger than that of InP, a conduction band discontinuity (in band lineup) is formed between the n-type InGaAs contact layer 1 and the n-type InGaAs layer 2 as shown in FIG. ΔE _C = 240 meV) occurs. Accordingly, an asymmetric electron energy barrier qφ _Bn = ΔE _C − (E _f −E _C ) of the InGaAs / InP junction of Formula 4 is generated. The barrier height from the InP to the InGaAs side depends on the voltage, but the barrier height from the InGaAs to the InP side hardly changes due to the voltage. A diode having rectification characteristics (= non-linearity) can be formed by this barrier.

The electron concentration of InGaAs (n-type InGaAs layer 2) at the InGaAs / InP interface is desirably high so that the voltage change of the barrier height _φBn due to the electron accumulation effect at the heterointerface is reduced. This is because, when the concentration is low, the electric field of the depleted InP (InP depletion layer 3) is shielded, and therefore, the barrier height φ _Bn ( = ΔE _C −E _F ) changes due to the bias.

で表すことができる。つまり、ｎ形ＩｎＧａＡｓ層２の電子濃度ｎ_ｅを変えてＥ_Ｆを上下させてバリア高さφ_Ｂｎを調整することで、ＨＢＤのＩ−Ｖ特性を変化させる（飽和電流Ｉ_Ｓと微分抵抗値Ｒ_Ｄを変化させる）ことができる。 The idea of the semiconductor device according to the present invention is that the electron concentration of InGaAs (n-type InGaAs layer 2) is deeply degenerated beyond the above-described range for preventing the “barrier height from being changed by bias”. The electron Fermi level (E _F ) is increased from the band edge of InGaAs (n-type InGaAs layer 2) to the band edge of InP (InP depletion layer 3). The IV characteristic of the HBD at this time is ideal,

Can be expressed as That is, by changing the electron density _{n e} of the n-type InGaAs layer 2 is lower the _{E F} and by adjusting the barrier height phi _Bn, changing the the I-V characteristic of the HBD (saturation current _{I S} and the differential resistance value _RD can be changed).

One approach to optimizing experimentally the electron concentration _{n e} of n-type InGaAs layer 2 of HBD is as follows. An n-type first semiconductor layer, a second semiconductor layer having a lower electron affinity than the first semiconductor layer, and an n-type third semiconductor layer are stacked in this order from the anode side to the cathode side, A plurality of diode structures having a heterojunction with the second semiconductor layer are formed. The electron concentration of the first semiconductor layer of each diode structure is changed by changing the doping amount when the first semiconductor layer is stacked. Then, the detection currents when a predetermined RF signal is input to these diode structures are plotted, and the electron concentration at which the detection current is maximized is found from the results.

  More specifically, when optimizing the HBD element, when the line impedance on the high frequency signal input side of the detection circuit or the antenna impedance of the pure resistance and the input impedance of the amplifier connected to the detection output are given in advance. Then, the doping amount of the first semiconductor layer is adjusted so as to maximize the output current detected by inputting the high-frequency signal. A plurality of diode structures with varying doping amounts are created as described above, and this is used as a detection circuit for the line impedance on the high frequency signal input side or the antenna impedance of the pure resistance and the input impedance of the amplifier connected to the detection output. The detection current when a predetermined RF signal is input is plotted, and the electron concentration at which the detection current is maximized is found from the result.

Further, if the configuration of the detection circuit including the HBD is the same, the optimum saturation current _IS is a constant value, so that the barrier height φ _Bn changes according to the heterojunction area S _j . Therefore, the electron concentration _{n e} of n-type InGaAs layer 2, when the junction area of the heterojunction required on the frequency characteristic and the _{S j (μm} ^2), to determine the number C1 as an index.

When determining the electron concentration _{n e} of such an n-type InGaAs layer 2, for a typical antenna impedance (75 ohms), it found that the best reception characteristic can be obtained over a wide amplifier input line impedance range 35~200Ω It was. For example, when S _j = 0.5 μm ² , n _e = 1.3 × 10 ¹⁹ (/ cm ³ ). In this condition, the Fermi level _{E F} is about 160meV rises from the conduction band edge. As a result, the electron energy barrier qφ _Bn = ΔE _C -E _F for effective electron becomes extremely low as 80 meV, _{I S} is extremely high as approximately 0.17mA over conventional HBD.

(Embodiment 2)
In the semiconductor element of this embodiment, the semiconductor element 301 of FIG. 1 further includes a semi-insulating semiconductor substrate. Specifically, the multilayer diode structure is formed on a semi-insulating semiconductor substrate so as to contact the fifth semiconductor layer. The anode electrode is in contact with the opposite side of the fourth semiconductor layer to the second semiconductor layer, and the fifth semiconductor layer has an area viewed from the stacking direction larger than the area of the third semiconductor layer, The cathode electrode is disposed on the third semiconductor layer side of the fifth semiconductor layer and at a position not in contact with the third semiconductor layer.

3 and 4 are schematic views for explaining the semiconductor element 302 of the present embodiment, which are a plan view and a cross-sectional view (AA ′ cross section) of the semiconductor element, respectively. Each semiconductor layer is as follows.
11: High concentration n-type InGaAs contact layer (fourth semiconductor layer)
12: n-type InGaAs layer (first semiconductor layer) whose electron concentration is adjusted as required
13: Low concentration InP depletion layer (second semiconductor layer)
14: High-concentration n-type InP (third semiconductor layer)
15: High concentration n-type InGaAs contact layer (fifth semiconductor layer)
16: Anode electrode 17: Cathode electrode 18: Semi-insulating semiconductor substrate 19: Wiring metal 20: HBD region Reference numerals 11 to 17 correspond to layers 1 to 7 in FIG.

In order to manufacture this HBD, all semiconductor layers are epitaxially grown by the MO-VPE method or the MBE method, and the substrate is patterned. By patterning the anode electrode 16 and using it as a mask, the underlying semiconductor layer is chemically etched, whereby an overhang shape as shown in the cross section of FIG. 4 can be produced. Since the size of the anode electrode 16 can be made larger than the junction size of the semiconductor layer, the wiring metal 19 can be easily patterned. The n-type InGaAs layer 12 as a mask, a low concentration of InP depletion layer 13, since the chemical etching the n-type InP14 high concentrations, becomes finer size, reduce the junction capacitance _{C j} of HBD.

(Embodiment 3)
5 and 6 are diagrams for explaining the semiconductor device 401 of the present embodiment.
The semiconductor device 401 includes an electrical connection line 9A that connects the electrical high-frequency input circuit 8A and the electrical output circuit 8B,
The semiconductor element 301 for connecting the cathode side to an electrical connection line 9A, connecting the anode side to a ground 9B, and outputting a detection signal obtained by detecting an electrical high frequency from the electrical high frequency input circuit 8A to the electrical output circuit 8B; Is provided. Each circuit and the like are as follows (the description in Embodiment 1 is omitted).
8A: Electric high frequency (RF) input circuit 8B: Electric output circuit 9A: Electric connection line 9B: Ground 9C: RF electric signal input port 9D: Detection output port

  In the semiconductor device 401, two electrode terminal pairs are formed between the cathode electrode 7 and the anode electrode 6 of the semiconductor element 301. One of the electrode terminal pairs is an electric RF input circuit 8A, and the other is an electric output circuit. 8B is connected and functions as a detection circuit.

The electrical RF input circuit 8A is, for example, a transmission line or an antenna. The detection voltage and current induced by the electrical RF signal are dominated by the RF voltage and the operating point applied to the authentic part of the HBD (parallel circuit of C _j and _RD ). By estimating what RF voltage reaches both ends of the HBD genuine part, the detection output characteristic can be evaluated.

Consider a case where the electrical RF input circuit 8A is a pure resistance antenna (impedance Zo = 75Ω). If this pure resistance antenna is directly connected to the HBD, this can be considered in the equivalent circuit of FIG. Determine the voltage induced in _RD for a constant RF input 31.

In the circuit of FIG. 6, the impedance of the input line is Zo = 75Ω, S _j = 0.5 μm ² , C _j = 1.85 fF, R _S = 10Ω, R _in = infinity (the output of the semiconductor device is in an open state). Assume. When constant RF power input, or when changing the _{I S} (= change the electron density of InGaAs), RF current induced in the differential resistance _{R D} of the HBD _{(I RF)} is changed to what kind the frequency Calculated [FIG. 7]. In FIG. 7, the horizontal axis represents the frequency of the RF input 31, and the vertical axis represents the RF current (I _RF ) induced in the differential resistance _RD .

In the case of qφ _Bn = 63 meV, although the voltage drop of the series resistor _RS is somewhat, since _RD is almost matched to the impedance of the line, the value is close to 0 dB in the low frequency region. On the other hand, as qφ _Bn = 80 meV and qφ _Bn = 138 meV, the Zo < _RD mismatch state is reached, so the current flowing through _RD decreases and the detection current also decreases directly. As described in the background section, the current sensitivity is unchanged if impedance matching is established. That is, when _RD increases and impedance mismatch increases, the detection current decreases. The detection current will be described again in the description of FIG.

For band (frequency characteristic) from the state determined by _C j · Zo in the case of mismatch, the shifts tend determined by _C j · _{R D} according to _{R D} decreases, it is more advantageous Qfai _Bn is small. Looking at 3dB reduction zone (f-3dB), f- 3dB = 1.1THz in qφ _Bn = 138meV it can be seen that the increase in f-3dB = 2.2THz in qφ _Bn = 63meV (in FIG. 7, respectively ○ mark on the frequency characteristics).

As described above, in a system that handles an actual high-speed signal, the detection output is often connected to a feedback amplifier, and its input impedance (R _in ) is typically 50Ω. Here, it is important to increase the detection current output in order to increase the S / N ratio.

It is possible to calculate how the detection output current behaves when the electron concentration n _e (= electron energy barrier qφ _Bn ) of the n-type InGaAs layer 2 is changed. FIG. 8A is the circuit of FIG. 6 where the impedance of the input line is Zo = 75Ω and R _in = 50Ω. In FIG. 8B, Zo = 250Ω and R _in = 500Ω. In these figures, the horizontal axis represents the electron density _{n e} of the n-type InGaAs layer 2, the vertical axis of the detection current outputted from the _HBD, a current output to the _{R in.} The RF input 31 is −30 dBm.

The detection current on the vertical axis is a current output to the R _in part by a detection circuit using _RD as a power source impedance. _{n e} of n-type InGaAs layer 2 is smaller, since the larger the qφ _{Bn I S} is also small detection current is reduced. On the other hand, if n _e is as exceeds the optimal region, R _D becomes relatively smaller compared with Zo. In such a state, the input high frequency is reflected (= the matching state deteriorates and the HBD terminal voltage decreases), and the detection current decreases. For this reason, as in FIGS. 8A and _8B, the detection current of _{R in} unit is Qfai _Bn value, i.e., will have a peak at a certain InGaAs electron density _{n e.} The series resistance R _S shows the case of 0Ω and the case of realistic values of 10Ω and 20Ω. Fluctuations in the optimum point of n _e due to the R _S is not too large.

In the example of non-feeding (= zero bias) operation in FIG. 8A, there is an optimum value (corresponding to qφ _Bn = 80 meV) in the vicinity of n _e = 1.3 × 10 ¹⁹ (/ cm ³ ). Electron concentration _{n e} of this time, the junction area _S j = _0.5μm ² since the number _C1, R D = 150 _ohms, corresponding to I S = 166μA. It can be seen that the detection current output gives the maximum value when the differential resistance _{RD of the} HBD is slightly higher than the state where the differential resistance _{RD of the} HBD is exactly matched to the input line impedance Zo = 75Ω.

In the example of the non-feeding (= zero bias) operation in FIG. 8B, there is an optimum value in the vicinity of n _e = 1.0 × 10 ¹⁹ (/ cm ³ ). As these examples, according to the given circuit condition, the peak of optimum n _e there exists and, as inferred from the number C1, n _e and log [√S _j] is a linear relationship It is important to have Note that S _j and optimal n _e described in the section of the description of the formula C1, the relationships expressed by a numerical value, the impedance Zo = 75 ohms of input lines, the input impedance of the amplifier when (high-speed signal Rin = 50 [Omega This corresponds to a reception detection circuit.

(Embodiment 4)
FIG. 9 is a diagram illustrating the semiconductor device 402 of this embodiment. A planar bowtie antenna is connected to the semiconductor device as the electrical RF input circuit 8B. Each circuit is as follows.
19: Wiring metal 20: HBD region 21: Bowtie antenna metal 22: Detection output line (one corresponds to the electrical connection line and the other corresponds to the ground)
23: Connection end The HBD region 20 of the present embodiment is the HBD region 20 described in FIG.

The wiring metal 19 extended from the HBD region 20 shown in FIG. 9 and the pattern end of the bow tie antenna metal 21 are connected. And when a circuit is comprised with a transmission line, the high impedance filter circuit which removes a high frequency is connected to the connection end 23 normally. Although the high-frequency signal input to the bow tie antenna includes a component that is back-radiated from the antenna, there is little coupling to the detection detection line 22 to which a high-impedance filter circuit is connected. That is, when viewed from the antenna side which is the electrical RF input circuit 8A, the detection output line 22 to which the electrical output circuit 8B is connected is in a high-frequency cut-off state.
On the other hand, when the antenna side is viewed from the connection end 23, the frequency of the connection end 23 is out of the band of the bow tie antenna, so that the low-frequency cut-off state occurs.
Therefore, it can be seen that the semiconductor device 402 has basically the same circuit configuration as the equivalent circuit (electrical RF input circuit 8A and HBD region 20) shown in FIG.

(effect)
As described above, the present invention provides a technique for improving the detection current output and the performance of the 3 dB band of a detection device that performs zero bias operation in a high frequency band, particularly in the THz frequency range. This is compared with the conventional HBD, to achieve a lower barrier height phi _Bn, increasing the saturation current I _S, be brought closer to the alignment of the differential resistance value R _D of the operating point with respect to the impedance of the RF input line This is a basic design method that optimally sets the detection current output. Since it is a diode composed only of a semiconductor, the problem of instability of characteristics derived from a barrier metal, which is a problem in SBD, is improved, and it is convenient to manufacture an array type sensor that requires a uniform detection output. good.

ここで、フェルミ準位の電子濃度依存性を次式で仮定する。

Ｇは係数である。
また、接合面積をＳ_ｊ＝Ｓ_ｊｕｍ×１０^−８（ｃｍ^２）として、ミクロン単位表記にすると、次式のように表現できる。

ＩｎＧａＡｓ／ＩｎＰヘテロ接合の場合、論文報告例からＧ＝１．２１×１０^−２０と推測され、本出願で典型的な高速検波回路の場合：
・入力ラインのインピーダンス：Ｚｏ＝７５Ω
・アンプの入力インピーダンス：Ｒ_ｉｎ＝５０Ω
の条件で最適となるのは、Ｉ_Ｓ（ｏｐｔｉｍｕｍ）＝１６６μＡ（本文中に説明あり）となる。
また、Ｖ_Ｔ＝０．０２５、ΔＥ_Ｃ＝０．２４／ｑを数Ａ３に代入すると次式となる。

数Ａ４は数Ｃ１に相当する。 [Appendix]
Derivation of the number C1 will be described.
Take log () on both sides of Equation 3.

Here, the electron concentration dependence of the Fermi level is assumed by the following equation.

G is a coefficient.
Further, when the junction area is expressed as a unit of micron with S _j = S _jum × 10 ⁻⁸ (cm ² ), it can be expressed as the following equation.

In the case of an InGaAs / InP heterojunction, G = 1.21 × 10 ⁻²⁰ is estimated from a paper report example, and in the case of a typical high-speed detection circuit in the present application:
・ Input line impedance: Zo = 75Ω
・ Input impedance of amplifier: R _in = 50Ω
Under the conditions, I _S (optimum) = 166 μA (explained in the text).
When V _T = 0.025 and ΔE _C = 0.24 / q are substituted into the number A3, the following equation is obtained.

The number A4 corresponds to the number C1.

[Appendix]
The following is a description of a semiconductor detection device that receives an RF electrical signal from the millimeter wave to the THz frequency band, more specifically, a low-noise and high-speed semiconductor detection device that operates at zero bias according to the present invention.
The present invention relates to a semiconductor detection device that receives an RF electrical signal in a high frequency band, and appropriately sets a saturation current _IS and a differential resistance value _RD at a zero bias operating point with a simple structure even with a small junction capacitance. The present invention provides means for improving the reception sensitivity of a detection receiving device.

<1>:
A heterojunction composed of a first n-type semiconductor and a second semiconductor, and a stacked diode structure in which a third n-type semiconductor serving as a contact layer in contact with the second semiconductor is disposed, to the first n-type semiconductor And an electrode terminal having an electrical contact with the third n-type semiconductor, and an area (S _j μm) of the heterojunction composed of the first n-type semiconductor and the second semiconductor. ² ) when given as the desired value
The structure is determined by adjusting the electron concentration of the first n-type semiconductor so as to maximize the detection current input to the amplifier connected to the subsequent stage with respect to a certain RF input. Semiconductor element.

<2>:
In the range <1> above,
The first n-type semiconductor is InGaAs, the second semiconductor is low concentration InP,
When the area (S _j μm ² ) of the heterojunction composed of the first n-type semiconductor and the second semiconductor is given,
The electron concentration (ne) of the first n-type semiconductor is
ne = 1.16 * 10 < ¹⁹ > -9.5 * 10 _< ¹⁸ > * log [(root) _Sj ] / cm _< ³ >.
A semiconductor element characterized by being determined according to:

<3>:
In the range of <1> and <2>, a third n-type contact layer is disposed in contact with the outside of the first n-type semiconductor of the multilayer diode structure, and the third n-type semiconductor A semiconductor device element, wherein a fourth n-type contact layer is disposed in contact with the outside, and each layer is formed on a substrate.

<4>:
An electric RF input circuit and a detection output circuit are connected to the two electrode terminal pairs in the ranges <1>, <2>, and <3>.

<5>:
A semiconductor device, wherein the electric RF input circuit is a planar antenna or a three-dimensional antenna formed on a substrate in the ranges <1>, <2>, <3>, and <4>.

301, 302: Semiconductor element (HBD)
401, 402: Semiconductor device

Claims (9)

An n-type first semiconductor layer, a second semiconductor layer, and an n-type third semiconductor layer are stacked in this order from the anode side to the cathode side, and the first semiconductor layer and the second semiconductor layer are heterojunction. A method of manufacturing a semiconductor device having a multilayer diode structure,
The first semiconductor layer is InGaAs,
The second semiconductor layer is InP,
When the area of the heterojunction is S _j (μm ² ), an electron concentration n _e (cm ⁻³ ) of the first semiconductor layer is defined by Formula C1.

An n-type first semiconductor layer, a second semiconductor layer, and an n-type third semiconductor layer are stacked in this order from the anode side to the cathode side, and the first semiconductor layer and the second semiconductor layer are heterojunction. A semiconductor device having a multilayer diode structure,
The first semiconductor layer is InGaAs;
The second semiconductor layer is InP;
A semiconductor element characterized in that when the area of the heterojunction is S _j (μm ² ), the electron concentration n _e (cm ⁻³ ) of the first semiconductor layer is Formula C1. The multilayer diode structure is
An n-type fourth semiconductor layer stacked on the anode side of the first semiconductor layer;
An n-type fifth semiconductor layer stacked on the cathode side of the third semiconductor layer;
Further comprising
The semiconductor device according to claim 2, wherein the multilayer diode structure is formed on a semi-insulating semiconductor substrate so as to contact the fifth semiconductor layer. An anode electrode and a cathode electrode;
The anode electrode is in contact with the second semiconductor layer opposite to the second semiconductor layer;
The fifth semiconductor layer has an area viewed from the stacking direction larger than the area of the third semiconductor layer,
4. The semiconductor element according to claim 3, wherein the cathode electrode is disposed on the third semiconductor layer side of the fifth semiconductor layer and at a position not in contact with the third semiconductor layer. 5.   The semiconductor element according to claim 4, wherein the anode electrode has an area as viewed from the stacking direction larger than an area of the fourth semiconductor layer.   6. The semiconductor device according to claim 4, wherein the first semiconductor layer has an area as viewed from the stacking direction larger than an area of the second semiconductor layer. An electrical connection line connecting the electrical high frequency input circuit and the electrical output circuit;
7. The method according to claim 2, wherein the cathode side is connected to the electric connection line, the anode side is connected to the ground, and a detection signal obtained by detecting an electric high frequency from the electric high frequency input circuit is output to the electric output circuit. A semiconductor element according to
A semiconductor device comprising:   The semiconductor device according to claim 7, wherein the electric high-frequency input circuit is an antenna.   9. The semiconductor device according to claim 8, wherein the electric high-frequency input circuit is a planar antenna formed on the semi-insulating semiconductor substrate.

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