TWI691095B - Dual band photodetector and manufacturing method thereof - Google Patents

Abstract

A dual band photodetector and a manufacturing method thereof are provided. The dual band photodetector includes a substrate, a first active layer, a second active layer, and an electrode layer. The first active layer is disposed on the substrate and has a first predetermined thickness, and the first active layer includes the first semiconductor material. The second active layer is disposed on the first active layer and has a second predetermined thickness, and the second active layer includes the second semiconductor material. The electrode layer is disposed between the first active layer and the second active layer. The first predetermined thickness is greater than or equal to the second predetermined thickness, and an energy gap of the second active layer is larger than an energy gap of the first active layer.

Description

Dual-band optical detector and preparation method thereof

The invention relates to a photodetector and a preparation method thereof, in particular to a dual-band photodetector and a preparation method thereof.

Please refer to FIG. 1, which is a conventional metal-semiconductor-metal (MSM) photodetector structure. A single-layer active layer O2 is provided on the substrate O1 of the conventional structure. An electrode portion O3 that senses a change in response is provided on O2.

In order to explain the structure of the photodetector shown in Figure 1, please refer to Figure 2, which is the metal-semiconductor-metal (MSM) photodetector structure of Figure 1 with a wavelength of 320nm The UV-A band up to 400nm is the incident band, and the dynamic spectrum response graph generated by periodically switching the illumination light switch to illuminate the detector, where the X axis is the measurement time in seconds and the Y axis is the normalized current (au ). As shown in Figure 2, the conventional photodetector structure is irradiated with light in the UV-A band, and the measurement current continues to increase until the light in the UV-A band is turned off. When the light in the UV-A band is turned off, the measurement The current gradually decreases until the UV-A band is turned on again and then rises again, which means that the change of the measurement current is synchronized with the change of the switch of the UV-A band. By this, the change of the measurement current value can be used to determine whether the photodetector structure is received. UV-A band incident light.

To further illustrate that the photodetector structure shown in Figure 1 also responds to light in other wavelength bands than the UV-A band, please refer to Figure 3, which is a conventional photodetector structure with an incident wavelength of 270nm to The static spectrum response graph of light in the 450nm band, where the wavelength of the incident light on the X axis is in nanometers and the unit of responsivity on the Y axis is per watt/ampere (W /A), the unit representing the intensity of incident light is watt (W), and the unit of current generated is ampere (A). As shown in the figure, in addition to the UV-A band, the conventional photodetector has a current response under the irradiation of the incident wave band of 270nm to 450nm, however, due to the following factors, it is difficult to identify other wave bands except the 320nm to 400nm band :

First of all, the conventional photodetector's responsivity of irradiated visible light varies with wavelength. Compared with the irradiated UV-A band, the responsivity of light responsive to wavelength does not change significantly. As shown in Figure 3, the irradiated light Visible light in the wavelength range of 400nm to 450nm exhibits a responsivity with wavelength that is close to horizontal. Therefore, when the conventional photodetector structure is used to distinguish the UV-A incident band and the visible light incident band, the response range to the visible light band The sensing feedback mechanism must be different from the sensing feedback mechanism in the UV-A band response range, and the sensing feedback mechanism in the visible light band response range must meet the accuracy requirements for identifying small response changes.

In addition, when the conventional photodetector irradiates UV-B light with an incident wavelength range of about 270nm to 320nm, the responsivity changes with the wavelength and the incident wavelength range of about 320nm to 400nm UV-A The light is reversed, which causes the conventional photodetector to receive the same response as UV-A light when it is irradiated by UV-B light, and it is impossible to distinguish UV-B light with an incident wavelength between 270nm and 320nm through the responsivity. UV-A light between 320nm and 400nm.

In summary, although the range of incident wavebands that a conventional photodetector structure can generate a response current is wide, only a specific waveband has a significant response change, and the trend of the response current of the incident waveband may not be consistent with the specific waveband. Therefore, when the conventional photodetector structure designs a sensing mechanism for resolving the incident light band, the range of the sensing band is easily limited to a specific band.

To improve the above-mentioned conventional technical problems, the present invention provides a dual-band photodetector, which includes a substrate, a first active layer, a second active layer, and an electrode layer. The first active layer is disposed on the substrate and has a first predetermined thickness. The first active layer includes a first semiconductor material. The second active layer is disposed on the first active layer and has a second predetermined thickness. The second active layer includes a second semiconductor material. The electrode layer is disposed between the first active layer and the second active layer. The first predetermined thickness is greater than or equal to the second predetermined thickness, and the energy gap of the second active layer is larger than the energy gap of the first active layer.

Optionally, the first semiconductor material contains zinc oxide.

Optionally, the first preset thickness is between 50 nm and 150 nm.

Optionally, the second semiconductor material contains magnesium zinc oxide.

Optionally, the molar ratio of oxygen (O):magnesium (Mg):zinc (Zn) of magnesium zinc oxide is 1:0.3~0.5:0.5~0.7.

Optionally, the thickness of the second active layer is between 20 nm and 80 nm.

Optionally, the electrode layer contains aluminum, nickel or gold.

Based on the above purpose, the present invention also provides a method for preparing a dual-band photodetector, which includes the following steps: depositing a first active layer on a substrate, and the first active layer having a first predetermined thickness; transmitting on the first active layer The yellow photolithography process defines the electrode area; depositing electrode material on the electrode area to form an electrode layer; depositing a second active layer on the first active layer and the electrode layer, and the second active layer has a second predetermined thickness; and etching to shift Except for a part of the second active layer; wherein, the first predetermined thickness is greater than or equal to the second predetermined thickness, and the energy gap of the second active layer is larger than the energy gap of the first active layer.

Optionally, the first active layer and the second active layer are deposited by a process including sputtering, chemical vapor deposition or spraying.

Optionally, the step of depositing the electrode material on the electrode area to form an electrode layer further includes: a step of defining a non-electrode area through the yellow photolithography process on the first active layer; and when both the electrode area and the non-electrode area are deposited When the electrode material is used, the electrode material on the non-electrode area is removed to expose the first active layer.

The advantages of the present invention are as follows:

(1) The dual-band photodetector of the present invention has a plurality of active layers. Since the detection band of incident light of the photodetector is determined according to the material energy gap of the active layer, in the dual-band photodetector of the present invention, the dual-band photodetector The photodetector includes a plurality of active layers, wherein each active layer has a different energy gap, so the sensing band of the dual-band photodetector of the present invention depends on the combination of ranges covered by the detection bands corresponding to the active layers, so that The dual-band photodetector of the present invention can have a larger detection band range and take into account detection accuracy.

(2) By replacing the materials of the first active layer and the second active layer of the dual-band photodetector of the present invention, the combination of the detection band to be sensed can be replaced, and it is convenient to design the sensing mechanism of the photodetector according to the detection band.

The advantages, features, and technical methods of the present invention will be described in more detail with reference to exemplary embodiments and drawings to make it easier to understand, and the present invention can be implemented in different forms, so it should not be understood that it is limited to what is stated here Embodiments, on the contrary, for those with ordinary knowledge in the technical field, the provided embodiments will make the disclosure more thorough and comprehensive and complete to convey the scope of the present invention, and the present invention will only be defined by the scope of the patent application .

The object of the present invention is to provide a structure of a photodetector, which can detect incident light in different wavebands, and can determine the type of incident light by sensing the magnitude of the photocurrent generated in response to the incident light.

Please refer to FIG. 4, which is a perspective view of the structure of an embodiment of the dual-band photodetector of the present invention. As shown in the figure, the dual-band photodetector 1 of the present invention includes a substrate 10, a first active layer 20, and an electrode layer 30与第一移动层40。 The second active layer 40. The first active layer 20 is disposed on the substrate 10, the first active layer 20 has a first predetermined thickness, and the first active layer 20 includes a first semiconductor material. The second active layer 40 is disposed on the first active layer 20 and has a second predetermined thickness. The second active layer 40 includes a second semiconductor material, wherein the second active layer 40 is farther from the substrate 10, that is, the second active layer 40 is closer to the illuminated side. The electrode layer 30 is disposed between the first active layer 20 and the second active layer 40.

The energy gap of the second active layer 40 is larger than that of the first active layer 20. When light in a band that meets the energy gap of the first active layer 20 is irradiated to the dual-band photodetector of the present invention, the first active layer 20 generates a response current. When the light that conforms to the second active layer band is irradiated to the dual-band photodetector 1, due to the difference in energy gap between the second active layer 20 and the first active layer 10, the energy gap of the second active layer 40 is satisfied, so that the first When the second active layer 40 generates incident light responding to the current and irradiates the first active layer 20, the energy gap of the first active layer 20 can also be satisfied, so that the first active layer 20 generates current, so the first active layer 20 and the second active layer 40 all produce response current. For example, because the wavelength of light in the UV-B band is shorter than the wavelength of light in the UV-A band, it has a larger energy, so it can provide a larger energy to overcome a larger energy gap. With the above arrangement, the second active layer 40 which has a larger energy level and needs to receive incident light of a shorter wavelength in order to respond is arranged close to the illumination side, and will have a smaller energy level and only need to receive a longer wavelength The incident light, that is, the responsive first active layer 20 is disposed at a position away from the illuminated side, to improve the problem of the difference in the transmittance of incident light resulting in the active layer not easily receiving light with an appropriate wavelength.

In an embodiment of the invention, the first predetermined thickness of the first active layer 20 is between 50 nm and 150 nm, preferably between 80 nm and 100 nm; the second predetermined thickness of the second active layer 40 Between 20 nm and 80 nm, preferably between 30 nm and 50 nm, when the second predetermined thickness is greater than 80 nm, the dual-band photodetector of the present invention cannot function.

In the structure of the dual-band photodetector 1 of the present invention, the detection characteristics of the dual-band photodetector 1 of the present invention are affected by adjusting the thickness of the first active layer 20. For example, the first predetermined thickness is greater than the second With the thickness set, the first preset thickness is fixed. The thinner the second preset thickness of the second active layer 40 near the illumination side, the better the light response of the second active layer 40, but the slower the response speed may be. That is, the better the static spectral response, the worse the dynamic response; and in another embodiment of the present invention, when the first preset thickness is close to the second preset thickness, the responsivity of the dual-band photodetector 1 is relatively high Small, but the response speed is fast, that is, the static spectrum response is poor, and the dynamic response is good. In addition, in another embodiment of the present invention, when the first preset thickness is less than the second preset thickness, the dual-band photodetector of the present invention cannot function. In other words, in different embodiments of the present invention, the first predetermined thickness and the second predetermined thickness can be adjusted according to the intended use of the photodetector.

In an embodiment of the invention, the second active layer 40 has a smaller area than the electrode layer 30, so that the electrode layer 30 is partially exposed outside the second active layer 40, so as to facilitate the measurement probe to contact the exposed electrode layer 30 Electrical measurement; however, in another embodiment of the present invention, the electrode layer 30 can be set to the same size as the second active layer 40, the first active layer 20, and the conductive layer 30, the measurement probe penetrates the contact electrode layer 30 Conduct electrical measurement on the side surface; or contact the side surface of the electrode layer 30 through a conductive portion protruding outside the conductive layer 30; or, in another embodiment of the present invention, the electrode layer 30 is arranged to expose at least two contact portions and Measuring probe contact.

In an embodiment of the present invention, the conductive layer 30 may be a mesh basket, a strip space basket or other basket structure with a gap portion, so that incident light can penetrate the second active layer 40 and pass through the gap portion The first active layer 20 is further irradiated.

Taking the detection band of the dual-band photodetector 1 of the present invention as the UV-A band and the UV-B band as an example, in an embodiment of the present invention, the band corresponding to the energy gap of zinc oxide (ZnO) is close to UV-A Band, so the first semiconductor material of the first active layer 20 far from the illumination side contains zinc oxide (ZnO); the energy gap of magnesium zinc oxide (MgZnO) corresponds to the band close to the UV-B band, so it is close to the second side of the illumination side The second semiconductor material of the active layer 40 includes magnesium zinc oxide (MgZnO), and the electrode layer 30 includes gold, nickel, gold, titanium gold, aluminum, or other electrode metals.

The detection bands of the dual-band photodetector 1 are the UV-A and UV-B bands. Further explanation, the thinner the second preset thickness of the second active layer 40 near the illumination side is, the dual-band photodetector 1 The better the light response when irradiated by the light of the UV-B band, but relatively, the response speed is poorer when irradiated by the light of the UV-B band, that is, the better the static spectrum response, the worse the dynamic response; and in the present invention In another embodiment, when the first preset thickness is close to the second preset thickness, the dual-band photodetector 1 is less responsive after being irradiated with light in the UV-A band and light in the UV-B band, But the response speed is faster, that is, the static spectrum response is poor, and the dynamic response is better. In addition, in another embodiment of the present invention, when the first preset thickness is less than the second preset thickness, the dual-band light detector cannot discriminate between UV-A band light and UV-B band light. In other words, the designer only needs to adjust the relationship between the first preset thickness and the second preset thickness to make the designed dual-band photodetector 1 suitable for different UV-A band and UV-B wave detection Field or detection purpose.

In some embodiments of the second semiconductor material of the present invention containing magnesium zinc oxide (MgZnO), the molar ratio of oxygen (O): magnesium (Mg): zinc (Zn) of magnesium oxide to zinc is 1:0.3 ~0.5: 0.5~0.7. Among them, the energy gap of magnesium zinc oxide can be adjusted by adjusting the ratio of oxygen, magnesium and zinc in magnesium oxide zinc, and then the spectrum range detected by the second active layer 40 can be adjusted. Among them, when the molar ratio of magnesium and oxygen in the second active layer is less than 0.3, the energy gap of magnesium zinc oxide is too small, resulting in the response wavelength of light in the UV-A band, which represents the inclusion of magnesium oxide containing zinc oxide The second active layer of the second semiconductor material does not respond to the light in the UV-B band, so that the entire photodetector still only responds to the light in the UV-A band, and cannot simultaneously detect the light in the UV-A and UV-B bands Effect.

The measurement method of the response current of the dual-band photodetector 1 of the present invention will be further described in FIG. 5 below.

Please further refer to FIG. 5, which is a static spectrum response diagram of an embodiment of the dual-band photodetector of the present invention. In the embodiment of FIG. 5, the selected second semiconductor material is Mg _0.3 Zn _0.7 O, electrode layer The cathode and anode of 30 are gold, the first semiconductor material is ZnO, the substrate material is silicon, and the thickness of the second active layer is 100 nm, and the thickness of the first active layer is 30 nm. As shown in the figure, when light of different wavelengths is irradiated, the current generated by the dual-band photodetector 1 of the present invention is also different. Among them, the responsivity unit of the Y axis is per watt/ampere, which means that the intensity of the incident light is watts, and the current is amperes. As shown in the figure, the incident light irradiated to the dual-band photodetector of the present invention is roughly divided into a visible light band (400 nm to 450 nm), a UV-A band (320 nm to 400 nm), and a UV-B band (250 nm to 320 nm).

To further explain, the difference from FIG. 3 is that the conventional photodetector produces a response change trend close to a linear pattern only in the UV-A band, and in the present invention, in the visible light band (400nm~450nm), UV -A-band (320nm~400nm), UV-B-band (250nm~320nm, in addition to different responsivity of the photodetector, and the change trend of responsivity is roughly linear as the wavelength of incident light decreases and the responsivity increase.

Please further refer to FIG. 6, which is a dynamic spectrum response diagram of an embodiment of the dual-band photodetector of the present invention, in which the wavelength of the irradiated UV-A light is 360 nm, the wavelength of the UV-B light is 300 nm, and the X axis is the amount The time it takes to measure, the Y axis is the normalized current (au), the measurement time is about 600 seconds, and the incident light UV-A is turned on and UV-A is turned off during the measurement period. And UV-B is turned on, UV-B is turned off.

In the embodiment of the present invention, since the wavelength of the light in the UV-A band is longer than the wavelength of the light in the UV-B band, it has a smaller energy and can only satisfy the first active layer 20 with a smaller energy gap , So that the first active layer 20 generates a photocurrent, in other words, when UV-A is turned on, only the first active layer 20 generates a photocurrent, so the measured current is lower; and due to the light in the UV-B band Is shorter than the wavelength of light in the UV-A band, so it has a larger energy, and can simultaneously satisfy the first active layer 20 with a smaller energy gap and the second active layer 40 with a larger energy gap, so that the first Both the active layer 20 and the second active layer 40 generate photocurrent. In other words, when UV-B is turned on, since both the first active layer 20 and the second active layer 40 generate photocurrent, the measured current is relatively high.

When UV-A is turned on (UV-A on), the measurement current is gradually increased to UV-A off (UV-A off), after UV-A is turned off, the measurement current is reduced, and then UV-B is turned on (UV-B on), the measurement current is gradually increased to UV-B off (UV-B off), after UV-B is turned off, the measurement current is reduced. Among them, the speed and response of the measurement current increase during the UV-B turn-on period is greater than that during the UV-A turn-on period, and the measurement current during the UV-B turn-off period is greater than the measurement current during the UV-A turn-off period. In this way, the user can distinguish whether the incident light band is UV-A or UV-B through the corresponding current change.

Please further refer to FIG. 7, which is a manufacturing flowchart of an embodiment of the dual-band photodetector of the present invention. As shown in the figure, it is a method for preparing a dual-band photodetector, which includes the following steps:

Step S1: deposit a first active layer on the substrate, and the first active layer has a first predetermined thickness. In step S1, the method for depositing the first active layer 20 includes spray coating, layer coating, chemical vapor deposition (CVD), or sputtering.

Step S2: define an electrode area on the first active layer through the yellow photolithography process. In step S2, the placement of electrodes defines the electrode positions defined by lithography and development.

Step S3: Deposit electrode material on the electrode area to form an electrode layer. In step S3, the electrode portions that form a difference are lifted off. The electrode layer includes gold, nickel, titanium gold, aluminum, or other electrode metals known to those having ordinary knowledge in the technical field. Among them, acetone can be used as a solvent for removal.

Step S4: deposit a second active layer on the first active layer and the electrode layer, and the second active layer has a second predetermined thickness. In step S4, the method for depositing the second active layer includes spray coating, layer coating, chemical vapor deposition (CVD), and sputtering. In one embodiment of the present invention, the growth environment of the first active layer 20 and the second active layer 40 is about 500 degrees Celsius. Among them, the carrier gas used for deposition is air.

Step S5: Etching to remove a part of the second active layer. For example, there is still a portion of the second active layer of the photoresist. The etching solution contains sulfuric acid and water in a volume ratio of 1:100.

The deposited first predetermined thickness is greater than or equal to the second predetermined thickness, and the energy gap of the second active layer is larger than the energy gap of the first active layer.

In another embodiment of the present invention, step S3 further includes the step of defining a non-electrode region through the yellow photolithography process on the first active layer, and removing electrode material when electrode material is deposited on both the electrode region and the non-electrode region The step of exposing the electrode material on the electrode area to expose the first active layer. Therefore, the area of the electrode layer of the present invention may be the same or smaller than the area of the first active layer.

In summary, the dual-band photodetector of the present invention has a plurality of active layers and can have a larger sensing band range while taking into account detection accuracy. In addition, by replacing the dual-band photodetector of the present invention An active layer and a second active layer material can sense any two kinds of incident light falling into the corresponding energy gap sensing range, and it is convenient to design the sensing mechanism of the photodetector according to the sensing light band.

The present invention can be implemented in different forms, so it should not be understood that it is limited to the embodiments set forth herein. On the contrary, for those of ordinary skill in the art, the provided embodiments will make the disclosure more thorough and comprehensive and The scope of the present invention is fully communicated, and the present invention is defined according to the scope of the patent application.

1: Dual band photodetector 10.O1: substrate 20: The first active layer 30: electrode layer 40: Second active layer S1~S5: Step O2: Active layer O3: electrode part

Figure 1 is a schematic diagram of the metal-semiconductor-metal photodetector of the prior art.

Figure 2 is a dynamic spectrum response diagram of a metal-semiconductor-metal structure photodetector of the prior art.

Figure 3 is a static spectrum response diagram of a prior art metal-semiconductor-metal structure photodetector.

FIG. 4 is a perspective view of the structure of an embodiment of the dual-band photodetector of the present invention.

Figure 5 is a static spectrum response diagram of an embodiment of the dual-band photodetector of the present invention.

FIG. 6 is a dynamic spectrum response diagram of an embodiment of the dual-band photodetector of the present invention.

FIG. 7 is a manufacturing flowchart of an embodiment of the dual-band photodetector of the present invention.

1: Dual band photodetector

10: substrate

20: The first active layer

30: electrode layer

40: Second active layer

Claims (10)

A dual-band photodetector includes: a substrate; a first active layer disposed on the substrate, having a first predetermined thickness, and including a first semiconductor material; and a second active layer disposed on The first active layer has a second predetermined thickness and includes a second semiconductor material; and an electrode layer disposed between the first active layer and the second active layer; wherein, the first The preset thickness is greater than or equal to the second preset thickness, and the energy gap of the second active layer is larger than the energy gap of the first active layer. The dual-band photodetector as described in item 1 of the patent scope, wherein the first semiconductor material includes zinc oxide (ZnO). The dual-band photodetector as described in item 1 of the patent application range, wherein the first preset thickness is between 50 nm and 150 nm. The dual-band photodetector as described in item 1 of the patent application range, wherein the second semiconductor material comprises magnesium zinc oxide (MgZnO). The dual-band photodetector as described in item 4 of the patent application scope, wherein the molar ratio of oxygen (O): magnesium (Mg): zinc (Zn) of magnesium oxide zinc is 1:0.3~0.5:0.5~0.7 . The dual-band photodetector as described in item 1 of the patent application range, wherein the second preset thickness is between 20 nm and 80 nm. The dual-band photodetector as described in item 1 of the patent application, wherein the electrode layer includes aluminum, nickel, gold or titanium gold. A method for preparing a dual-band photodetector includes the following steps: depositing a first active layer on a substrate, and the first active layer has a first predetermined thickness; through the first active layer through a The yellow photolithography process defines an electrode area; depositing an electrode material on the electrode area to form an electrode layer; depositing a second active layer on the first active layer and the electrode layer, and the second active layer has a first Two preset thicknesses; and etching to remove a part of the second active layer; wherein, the first preset thickness is greater than or equal to the second preset thickness, and the energy gap of the second active layer is lower than that of the first active layer The energy gap of the layer is large. The method for preparing a dual-band photodetector as described in item 8 of the patent application scope, wherein the first active layer and the second active layer are deposited by a process including sputtering, chemical vapor deposition, or spraying, respectively. The method for preparing a dual-band photodetector as described in item 8 of the patent application scope, wherein the step of depositing the electrode material on the electrode area to form an electrode layer further comprises: transmitting the yellow light lithography on the first active layer The process defines a step of a non-electrode area; and when the electrode material is deposited on both the electrode area and the non-electrode area, the step of removing the electrode material on the non-electrode area to expose the first active layer.

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