JPH0728046B2 - Semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (Industrial field of application) The present invention is easy to manufacture and has a high performance such as a photoelectric device, a photodetector, an N-type and P-type field effect transistor, a phototransistor and a combination thereof. The present invention relates to semiconductor devices such as bias photodetectors, non-biased phototransistors, complementary circuits, and optoelectronic circuits.

(Summary of the Invention) The present invention provides a photovoltaic semiconductor device using a PN junction formed on a substrate, which has a smaller band energy gap between the P and N semiconductors than the P and N semiconductors. A non-doped or low-doped third semiconductor layer is provided, and a P-type ohmic contact and an N-type ohmic contact for each carrier layer formed near the interface are formed with respect to the third semiconductor layer. Then, there is provided a semiconductor device characterized by constituting a photovoltaic device.

The present invention provides a photovoltaic semiconductor device using a PN junction formed on a substrate, which has a band energy gap between the PN junctions smaller than that of P-type and N-type semiconductors and is non-doped or A low-doped third semiconductor layer is provided, two N-type ohmic electrodes for each carrier layer formed near the interface are formed on the third semiconductor layer, and a bias voltage is applied between the electrodes. To form a photocurrent detection device, and to form P-type and N-type ohmic electrodes for each carrier layer formed near the interface with the third semiconductor layer in another region of the same crystal, It is an object of the present invention to provide a semiconductor device, which constitutes a photovoltaic device, uses the photovoltaic device as a bias power source of the photocurrent detection device, and constitutes a non-biased photocurrent detection device.

(Problems to be Solved by Prior Art and Invention) (a) As a photovoltaic semiconductor device using a PN junction,
As shown in FIG. 11, conventionally, there has been provided an element in which a P-type semiconductor 1 and an N-type semiconductor 2 are directly provided with contact electrodes 4 and 5, respectively. (Reference: JR Davis et al: Conf.Rec. 7th Ph
otovoltaic Spec.Conf. (9618) p.85) However, since an electromotive force is generated between the P-type semiconductor 1 and the N-type semiconductor 2 in this element, the contact electrodes are essentially The PN junction surface 3 must be attached on the opposite side, which is disadvantageous in increasing the size of the light receiving surface for higher performance.

In addition, carriers such as electrons and holes generated by light irradiation must be conducted by diffusion in the impurity crystal in the direction perpendicular to the PN junction plane by diffusion as shown in the principle diagram shown in Fig. 12. The resistance was large and the carrier was lost due to recombination, etc., and it was difficult to increase the photovoltaic-electromotive force conversion efficiency. In the figure, 6 is excitation light, 7 is photoexcited electrons, 8 is photoexcited holes, 9 is N-type semiconductor, and 10 is P-type semiconductor.

(B) Further, as a photocurrent detection device utilizing the photoconductive effect, as shown in FIG.
There is a device in which N-type ohmic electrodes 13 and 14 are formed and the excitation current by the excitation light 11 is detected. (Reference: RHBub
e et al.:Phys.Rev.128 (1962) 532) In this case, the photocurrent flowing in the semiconductor is small due to the scattering of electrons by impurities in the semiconductor.

(C) On the other hand, as a non-biased photodetector which does not need to apply a bias voltage for photodetection from the outside, the electron 16 generated by the excitation light 15 is conventionally generated as shown in FIG.
Was collected by the internal electric field of the crystal, and this hetero interface used the electromotive force between the channel and the substrate as the bias voltage. In the figure, 17 is a photoexcitation hole and 18 is N-AlGaAs.
Side, 19 is a non-doped (P ⁻ , N ⁻ ) GaAs side, 20 is a hetero interface, and 21 is a two-dimensional electron gas. (Reference: CYChen
et al: Appl.Phys.Lett.41 (3) p282 (1982)) This is because of the defect in device formation that electrodes must be caught on the substrate side, as shown in FIG. In addition, it is difficult to form a planar structure together with other elements on the same crystal film.

In addition, conventional photocells, photodetectors, phototransistors, electronic circuits, etc. made of general semiconductors have various required crystal layer structures and electrode installation methods. Therefore, they are combined in a planar form on the same crystal substrate. It had the drawback of being difficult to do.

(D) Further, both types of transistors using N-type and P-type carriers generated at the semiconductor hetero interface (reference: TM
imura et al: Jan.J.Appl.Phys.20 (1981) p598, HLSto
mer et al: Appl.Phys.Lett.44 (11) 1, (1984) p1062)
As a method of constructing a complementary circuit by, as a method that can be easily inferred from conventional individual devices,
As shown in Fig. 16, it is possible to stack individual devices in multiple layers, but this is a drawback that the crystal quality of the upper layer crystal deteriorates in terms of crystal growth, and the process is non-planar and the process becomes complicated, There were many defects such as wiring breaks due to steps. In the figure, 85 is a substrate, 86 is P-AlGaAs, 87
The non-doped ^{(P -, N -) GaAs} , 88 are N-AlGaAs, 89 is 2
Dimensional hole gas, 90 is two-dimensional electron gas, 91 and 93 are source and drain electrodes, 92 is a gate electrode, 94 and 96 are sources,
Drain electrode, 95 is gate electrode, 97 is P channel FET, 9
8 indicates an N channel FET.

(Means for Solving Problems) It is an object of the present invention to prevent deterioration of characteristics due to a carrier traveling in an impurity-doped semiconductor in a PN junction photovoltaic device, and to provide a planar type electrode. Except for restrictions on the process and element structure that come from the installation position,
It is to realize a simple and high-performance photovoltaic device, and to use it to realize a high-performance non-biased photocurrent detector and non-biased phototransistor. At the same time, a simple planar N-type and P-type threshold-controllable field-effect transistor is formed using the same crystal to realize a complementary circuit, and the various elements described above are the same. It is to realize optoelectronic circuits by combining them on a crystal.

In order to achieve the above-mentioned object, the present invention provides a non-doped third semiconductor having a small energy gap between PN junctions and utilizes the conduction of a two-dimensional gas generated at a hetero interface to form a photoexcited crystal. The first main feature is that the carrier accelerated by the internal electric field is made to run parallel to the crystal film surface and in the non-doped semiconductor.
It differs from the prior art in that the crystal layer structure is provided with the third semiconductor and that the ohmic electrodes are all provided on the same surface of the crystal.

(Example) Next, the Example of this invention is described. Needless to say, the embodiment is merely an example, and various modifications and improvements can be made without departing from the spirit of the present invention.

(I) FIG. 1 is a schematic diagram of a crystal structure of an example according to the present invention, and FIG. 2 is a band diagram thereof.

As shown in FIG. 1, when undoped GaAs30 is sandwiched between P-doped Al _0.5 Ga _0.5 As29 and N-doped Al _0.5 Ga _0.5 As31, P-Al _0.5 Ga _0.5 of GaAs 30 is formed as shown in FIG. Two-dimensional hole gas 40, N-Al _0.5 Ga _0.5 As on As29 side hetero interface
A two-dimensional electron gas 39 is generated at the side hetero interface. Reference numeral 35 denotes a substrate, and 36 denotes a light irradiation surface.

Here, a potential gradient occurs in the non-doped GaAs 42 as shown in FIG. 2, and accordingly, an extremely large internal electric field is generated. As an example, undoped
Assuming a GaAs layer thickness of 1000Å and a GaAs band energy gap of 1.4 eV, the calculated average internal interface is 140 KV / cm.
Also reaches. 41 indicates N-AlGaAs and 43 indicates P-AlGaAs.

Therefore, when electrons 37 and holes 38 are generated in the non-doped GaAs layer 42 by the light irradiation 44, the carriers in each of the carriers flow into the hetero interface at a saturated velocity due to the large internal electric field. Therefore, P-type and N-type ohmic contacts are ion-implanted with Be ions, Si ions, etc., and AuZnNi / Ti / Au,
When formed on a crystal film plane by an alloy of AuGe / Ni and electrically connected, a maximum of ~ 1.4V (GaAs band energy gap) between both electrodes is obtained as shown in FIG. Photovoltaic is generated. In the figure, 45 is a P-type ohmic electrode, 46 is an N-type ohmic electrode, 47 is mesa separation, 48 is excitation light, and 49 is a light irradiation semiconductor. Unlike the conventional PN junction photovoltaic cell, the carrier that conducts the hetero interface parallel to the plane of the crystal film has a small impurity scattering and low resistance because the channel is in non-doped GaAs, and recombination is also difficult. Therefore, the photovoltaic-electromotive force conversion efficiency becomes extremely good.
Also, the total number of carriers generated is proportional to the light receiving area,
It is different from the conventional device in that the light receiving surface can be arbitrarily increased in size due to the planar structure.

(II) On the other hand, as shown in FIG. 4, two N-type ohmic electrodes 55, 56 are formed on the crystal, and these electrodes 55,
When a bias voltage 52 is applied between 56 and irradiation light 50 is applied to the semiconductor region 54 sandwiched between these electrodes to excite the carrier, a photocurrent 53 flows between both electrodes. Regarding the conduction from the generation of the carrier to the hetero interface and the conduction on the hetero interface in this case, the carrier photo-excited by the large internal electric field of the crystal is accelerated first, and then the carrier is the non-doped crystal with less impurity scattering. Since the hetero interface flows at a high speed, the detection speed and detection efficiency are improved as compared with general ones.

(III) FIG. 5 shows a non-biased photodetector using the same crystal and using the photocell shown in (I) as the bias voltage source of the photocurrent detector shown in (II). This is an example of the case. In the figure, 57 is excitation light, 58 is mesa separation,
59 is an N-type ohmic electrode, 60 is a P-type ohmic electrode, 6
Reference numeral 1,62 denotes an N-type ohmic electrode, and 63,64 denote light irradiation semiconductors. That is, N-type ohmic electrode 59, P-type ohmic electrode
The photoelectromotive force generated between 60 is applied as a bias between the N-type ohmic electrodes 61 and 62. Here, assuming that the photovoltaic voltage between the electrodes 59 and 60 is 1.4 V and the distance between the electrodes is 5 μm,
An electric field of about 3 KV / cm works on the carrier at the hetero interface,
Can fully accelerate the carrier.

In this way, the bias-free photodetector can be easily realized only by the wiring combination between the various ohmic electrodes arranged on the plane.

(IV) In FIG. 6, the photodetector shown in (II) is formed by using the same crystal, and a Schottky key of Ti, Au, etc. is formed on the semiconductor 68 between the two ohmic electrodes 66, 67. This is an example in which a gate electrode 69 is provided to form an N-type field effect transistor or a phototransistor. 65 indicates mesa separation.

The band diagram under the gate electrode in this case is
As shown in the figure, the mechanism for controlling the two-dimensional gas at the hetero interface by the voltage applied to the gate is the same as that of a normal two-dimensional electron gas heterostructure FET.

Therefore, a high-performance phototransistor can be formed by using a highly transparent gate electrode. The phototransistor functions like a normal field effect transistor unless it is irradiated with light. Further, as in (III), an unbiased phototransistor can be formed by combining with a photovoltaic cell formed in the same crystal.

FIG. 7 shows a band diagram. Figure 70 is a gate electrode, 71 is N-AlGaAs, 72 is non-doped ^{(P -, N -) GaAs} , 7
3 is P-AlGaAs, 143 is a two-dimensional electron gas, 144 is excitation light, 1
45 indicates a photoexcited electron.

(V) Based on the same principle as in FIG. 7, by negatively applying the gate voltage to control the concentration of the two-dimensional hole gas generated at the hetero interface with the P-type crystal (see FIG. 8), The P-type transistor can also be composed of the same crystal. In FIG. 8, 99 is a gate electrode and 100 is P-AlGaA.
s, 101 is non-doped ^{(P -, N -) GaAs} , 102 are N-AlGaAs,
103 is a two-dimensional electron gas and 104 is a two-dimensional hole gas.
In this case, a P-type ohmic electrode is used.
Since the N-type and P-type transistors can also be formed in a planar type on the same crystal, a complementary circuit can be constructed much more easily than the conventional one (see FIG. 9). In FIG. 9, 105 is a substrate, 106 is P-AlGaAs,
107 is undoped AlGaAs, 108 is N-AlGaAs, 109 is undoped AlGaAs, 110 is undoped GaAs, and 111 is undoped.
GaAs, 112 is a two-dimensional hole gas, 113 is a two-dimensional electron gas,
114, 116 are P-type ohmic electrodes, 115 are gate electrodes, 117,
119 is an N-type ohmic electrode, 118 is a gate electrode, and 120 and 121.
Is a P ion implantation region, 122 and 123 are N ion implantation regions, 124
Indicates isolation between elements.

In the complementary circuit configuration by this method, N
By controlling the doping concentration of the N-type and P-type transistors or the amount of recess etching under the gates of both N-type and P-type transistors (see FIG. 10), there is an advantage that threshold values can be matched and high performance can be achieved. In FIG. 10, 125 is a substrate and 126 is N-
AlGaAs, 127 is undoped AlGaAs, 128 is undoped GaA
s and 129 are non-doped AlGaAs, 130 is P-AlGaAs, 131 is non-doped GaAs, 132 and 134 are P-type ohmic electrodes, 133 is a gate electrode, 135 and 137 are N-type ohmic electrodes, 136 is a gate electrode, 138 is a two-dimensional hole gas, 139 Is a two-dimensional electron gas,
Reference numerals 140 and 141 denote recess etching, and 142 denotes element isolation. Alternatively, a method of using Ni as the gate metal to cause the metal to sink by heat treatment and controlling the threshold value can also be applied.
(Reference: IEEE.EDL.Vol.EDL-5 No.7 1984p241) Furthermore, as will be described later, by using a P-type semiconductor as an upper layer and an N-type semiconductor as a lower layer, leakage due to parallel conduction due to P-type contamination. Since the influence of the current can be removed, there is an advantage in reducing the power consumption of the circuit.

(VI) Photocell, photocurrent detector, N type and P
Since the field effect transistor and the phototransistor can be formed in a planar shape using the same crystal, various optoelectronic circuits can be formed by combining them on the same wafer.

(VII) The layer structure of the crystal used above is, as shown in FIGS. 9 and 10, Al near the hetero interface.
Reducing the impurity concentration of _0.5 Ga _0.5 As is effective in improving the device performance by suppressing the effects of impurity diffusion and scattering.
The Al composition ratio of the mixed crystal may be other than 0.5. Further, regarding P and N semiconductors, the doping concentration to these is distributed so that it becomes larger as it is closer to the hetero interface and smaller as it is far, and the PN semiconductor layer is depleted just by supplying the carrier to the hetero interface. Then, when an ohmic contact is made, it is not necessary to spread parallel conduction other than high mobility two-dimensional gas.

In general, since an MBE crystal has a P ⁻ -type contamination, as a method for preventing P-type parallel conduction, there is a method in which the upper layer of the crystal is P-type and the lower layer is N-type. According to this structure, the P-type parallel conduction can be easily removed without making the P-type ohmic too deep in the crystal thickness direction. Providing a protective non-doped GaAs layer as a cap on the Al _0.5 Ga _0.5 As surface can prevent surface oxidation and the like.

(Effect of the Invention) As described above, according to the present invention, the internal electric field acting on the photoexcited carrier is large, and the characteristic deterioration due to impurity scattering and recombination due to the use of the two-dimensional electron gas and the two-dimensional hole gas is small. , A high-performance photovoltaic device, a photocurrent detection device, a phototransistor, and a non-biased photodetector, a non-biased phototransistor and the like by combining them can be configured in a planar type which can be easily manufactured on the same crystal. This can be applied to optical sensors, optical power supplies, etc.

Furthermore, high-performance N-type and P-type field-effect transistors using a high-mobility two-dimensional gas as a carrier are formed on the same crystal in a threshold-matching manner, and a high-performance complementary circuit is also formed. Can be configured as a planar type. It is possible to realize a high-performance optoelectronic circuit by combining these various optoelectronic elements on the same crystal and apply it to optical communication equipment such as computers and repeaters.

[Brief description of drawings]

FIG. 1 is a diagram showing a crystal structure of a photovoltaic device according to the present invention, and FIG. 2 is a band diagram showing the principle of the photovoltaic device which best represents the first feature of the present invention.
FIG. 4 is a configuration diagram of a photovoltaic device according to the present invention, FIG. 4 is a configuration diagram of a photocurrent detection device according to the present invention, FIG. 5 is a configuration diagram of a non-biased photocurrent detection device according to the present invention, and FIG. FIG. 7 is a configuration diagram of an (optical) field effect transistor according to the invention, FIG. 7 is a band diagram showing the principle of the (optical) field effect transistor according to the invention, and FIG. 8 is a complete diagram showing the second feature of the invention. FIG. 9 is a band diagram showing the principle of a mental circuit, FIG. 9 is an embodiment of the complementary circuit structure according to the present invention, FIG. 10 is another embodiment of the complementary circuit structure according to the present invention, and FIG. 11 is a conventional PN junction. Fig. 12 is a schematic diagram of a photovoltaic device, and Fig. 12 is a band diagram showing the principle of a conventional PN junction photovoltaic device.
13 is a schematic diagram of a conventional photocurrent detector, FIG. 14 is a band diagram showing the principle of a conventional non-biased photocurrent detector, FIG. 15 is a schematic diagram of a conventional non-biased photocurrent detector,
FIG. 16 shows a schematic diagram of the configuration of a conventional complementary circuit. 1,10 …… P-type semiconductor 2,9,13,14 …… N-type semiconductor 3 …… PN junction surface 4,32,45,60,91,93,114,116,132,134 …… P-type ohmic electrode 5,22,23,33 , 46,55,56,59,61,62,66,67,94,96,117,119,1
35,137 …… N-type ohmic electrode 6,11,15,34,44,48,50,57,144 …… Excitation light 7,16,37,145 …… Photoexcited electron 97 …… P channel FET 98 …… N channel FET 8,17 , 38 …… Photoexcitation hole 12,24,36,49,54,63,64 …… Light-irradiated semiconductor 25 …… Conductive layer 47,51,58,65 …… Mesa separation 18,31,41,71,88,102,108,126 ...... N-AlGaAs 107,109,127,129 ...... undoped ^{(P -, N -) AlGaAs} 19,30,42,72,82,101,110,111,128,131 ...... undoped ^{(P -, N -) GaAs} 20 ...... hetero interface 120,121 ...... P ⁺ ion implantation region 122,123 …… N ⁺ ion implantation region 21,39,90,103,113,139,143 …… two-dimensional electron gas 40,89,104,112,138 …… two-dimensional hole gas 124,142 …… isolation between elements 26,52 …… bias voltage 27,53 …… photocurrent 140,141… … Recess Etch 29,43,73,86,100,106,130 …… P-AlGaAs 35,85,105,125 …… Buffer layer, substrate 69,70,92,95,99,115,118,133,136 …… Gate electrode

─────────────────────────────────────────────────── ─── Continuation of the front page (51) Int.Cl. ⁶ Identification number Office reference number FI technical display location 7630-4M H01L 31/08 L

Claims (2)

[Claims] 1. A photovoltaic semiconductor device using a PN junction formed on a substrate, wherein a band energy gap between the PN junctions is smaller than that of a P-type semiconductor and an N-type semiconductor and is non-doped. Alternatively, a low-doped third semiconductor layer is provided, and a P-type ohmic contact and an N-type ohmic contact for each carrier layer formed near the interface are formed on the third semiconductor layer, respectively. A semiconductor device comprising a photovoltaic device. 2. A photovoltaic semiconductor device using a PN junction formed on a substrate, wherein a band energy gap between the PN junction is smaller than that of a P-type semiconductor and an N-type semiconductor, and is non-doped. Alternatively, a low-doped third semiconductor layer is provided, two N-type ohmic electrodes for each carrier layer formed near the interface are formed on the third semiconductor layer, and between the electrodes. A bias current is applied to form a photocurrent detection device, and P-type and N-type ohmic electrodes for each carrier layer formed near the interface with the third semiconductor layer in another region of the same crystal are formed. And a photovoltaic device, wherein the photovoltaic device is used as a bias power source of the photocurrent detection device to form a non-biased photocurrent detection device.