KR102485133B1 - High efficiency nitride-based photo detector - Google Patents

Abstract

An object of the present invention is to provide a photodetector in which a photoexcitation current increases or decreases according to a gate voltage applied to a gate electrode in a semiconductor device having an AlGaN/GaN heterojunction thin film structure. The present invention is a substrate; an Al _y Ga _1-y N channel layer present on top of the substrate; and an n-type Al _x Ga _1-x N barrier layer present on top of the channel layer, and a gate electrode, a source electrode, and a drain electrode are formed on the n-type Al _x Ga _1-x N barrier layer. The gate electrode is disposed between the source electrode and the drain electrode, and x and y satisfy 0≤y<x, 0<x<1 and 0≤y<1, and applied to the gate electrode Provided is a photodetector characterized in that a photoexcitation current increases or decreases according to a gate voltage.

Description

High-efficiency nitride-based photodetector {HIGH EFFICIENCY NITRIDE-BASED PHOTO DETECTOR}

The present invention relates to a highly efficient nitride-based photodetector.

Recently, nitride semiconductors have been spotlighted not only as semiconductor optical devices but also semiconductor electronic devices such as high-mobility transistors, power semiconductors, and sensors due to their excellent physical and chemical properties. Among them, GaN material has a bandgap energy of 3.4eV, and when used as an optical sensor, detection in the ultraviolet region of about 365nm is possible. These GaN-based optical sensors are manufactured in various structures such as a metal-nitride semiconductor-metal structure, a Schottky diode structure, and a PN junction structure. Recently, with the arrival of the 4th industrial revolution, the sensor industry is expanding, and one-chip composite sensors in which several elements are assembled are being manufactured. Accordingly, fast response speed and high sensitivity characteristics for one chip are required, and research on an optical sensor having an AlGaN/GaN heterojunction structure as shown in FIG. 1 is being conducted.

A general nitride semiconductor optical sensor consists of an M-S-M (metal-nitride-metal) structure consisting of an electrode that satisfies an Ohmic contact and a semiconductor surface after forming a high-quality GaN thin film on a sapphire substrate. Therefore, when light is injected into the GaN thin film from the outside, electrons and holes are formed on the metal surface by the photoelectric effect, and the resistance of the GaN thin film is changed by the electrons generated by the external light to operate. In order to improve the current formed by the injected light, the area into which the light is injected is enlarged by changing the structure of the electrode or the area into which the light is injected is increased by changing the structure of the GaN thin film where the photoelectric effect occurs. By doing so, the value of the photocurrent formed by light injection and the photosensitivity are improved.

For example, as shown in (a) of FIG. 2, if the structure of the electrode is first manufactured in an interdigitated structure, the light reactivity is improved by expanding the area where light is injected in the GaN thin film region where the reaction occurs do. In addition, as shown in (b) of FIG. 2, the photoreactivity is improved by growing a two-dimensional nanostructure rather than a one-dimensional thin film structure between electrodes to widen the surface area of the portion where the reaction occurs. However, although all of these structures have a higher light response compared to sensors having a simple thin film structure, there is a limit to the response time. Accordingly, recent research groups are conducting optical sensor research using a structure having high electron mobility characteristics by using a heterojunction structure of a GaN thin film and an AlGaN thin film. This GaN/AlGaN heterojunction structure is shown in (a) of FIG.

As shown in (b) of FIG. 3, when the AlGaN and GaN thin films are bonded, the Fermi energy is matched by the difference in piezoelectric polarization and lattice constant of the two materials, and strong band bending occurs at the junction, and in this region It has a very high electron density. This is called a two-dimensional electron gas channel (2DEG). In this way, when AlGaN and GaN materials are bonded, a two-dimensional electron gas channel is generated at the interface, and has a very high electron mobility characteristic compared to a general single GaN thin film, so that a light sensor using this can have a fast response time. there is. Additionally, in the case of this heterojunction, when light is injected from the outside, the energy region in which light absorption occurs in the GaN thin film and the energy region in which light absorption occurs in the AlGaN thin film are different, so light absorption occurs in two energy regions, so dual wavelength light It can also be used as a sensor.

The existing AlGaN/GaN heterojunction structure has high electron mobility and is widely used in power semiconductors and RF devices. At this time, since the thicker the thickness of the AlGaN thin film, the stronger the two-dimensional electron gas layer is formed. Therefore, while using the AlGaN thin film with a thickness of 20 nm or more, research on the high electron mobility transistor focusing on the efficiency reduction characteristic due to the difference in lattice constant with the GaN thin film is being conducted. has been progressing

An object of the present invention is to provide a photodetector in which a photoexcitation current increases or decreases according to a gate voltage applied to a gate electrode in a semiconductor device having an AlGaN/GaN heterojunction thin film structure.

The present invention, a substrate; an Al _y Ga _1-y N channel layer present on top of the substrate; and an n-type Al _x Ga _1-x N barrier layer present on top of the channel layer, and a gate electrode, a source electrode, and a drain electrode are formed on the n-type Al _x Ga _1-x N barrier layer. The gate electrode is disposed between the source electrode and the drain electrode, and x and y satisfy 0≤y<x, 0<x<1 and 0≤y<1, and applied to the gate electrode Provided is a photodetector characterized in that a photoexcitation current increases or decreases according to a gate voltage.

The n-type Al _x Ga _1-x N barrier layer may have a thickness of 15 nm or less.

When the applied gate voltage is a negative voltage, an optical excitation current may increase.

The photodetector may detect light having a wavelength of 280 nm or more and 400 nm or less.

The present invention, a substrate; an Al _y Ga _1-y N channel layer present on top of the substrate; and a p-type Al _x Ga _1-x N barrier layer present on top of the channel layer, wherein a gate electrode, a source electrode and a drain electrode are formed on the Al _x Ga _1-x N barrier layer. A gate electrode is disposed between the source electrode and the drain electrode, x and y satisfy 0≤y<x, 0<x<1 and 0≤y<1, and a gate voltage applied to the gate electrode It is possible to provide a photodetector characterized in that the photoexcitation current increases or decreases according to.

The p-type Al _x Ga _1-x N barrier layer may have a thickness of 15 nm or less.

When the applied gate voltage is a positive voltage, an optical excitation current may increase.

The photodetector may detect light having a wavelength of 280 nm or more and 400 nm or less.

According to the present invention, in a semiconductor device having an AlGaN/GaN heterojunction thin film structure, a photodetector in which a photoexcitation current increases or decreases according to a gate voltage applied to a gate electrode may be provided.

1 shows an AlGaN/GaN heterojunction optical sensor.
FIG. 2 (a) shows a GaN-based optical sensor manufactured in an interdigitated structure with an electrode structure, and FIG. 2 (b) shows an optical sensor in which a two-dimensional nanostructure is grown between electrodes. .
Figure 3 (a) shows an optical sensor having a GaN/AlGaN heterojunction structure, and Figure 3 (b) shows a two-dimensional electron gas channel formed at the junction when GaN and AlGaN heterojunction.
4 (a) to (c) show photodetectors of an AlGaN/GaN heterojunction structure in which the thickness of the Al _x Ga _1-x N barrier layer is 10, 20, and 30 nm, respectively.
Figure 5 (a) shows the 2DEG density according to the thickness of the Al _x Ga _1-x N barrier layer, Figure 5 (b) shows the electron mobility according to the thickness of the Al _x Ga _1-x N barrier layer .
6(a) shows a voltage-current curve before externally injecting ultraviolet rays, and FIG. 6(b) shows a voltage-current curve after externally injecting ultraviolet rays.
FIG. 7 shows photoexcitation current values as the thickness of the Al _x Ga _1-x N barrier layer is changed to 10, 20, and 30 nm when the applied voltage is 3V.
8 shows the number of electrons formed by the two-dimensional electron gas channel according to the thickness of the Al _x Ga _1-x N barrier layer.
9 shows photoreactivity curves according to wavelength in AlGaN/GaN high electron mobility transistor devices having 10, 20, and 30 nm Al _x Ga _1-x N barrier layers.
Figures 10 (a) to (c) are high electron mobility transistor devices having 10, 20, and 30 nm Al _x Ga _1-x N barrier layers, respectively, according to the gate voltage before and after light is injected from the outside. A voltage-current curve is shown.
FIG. 11 (a) shows the photocurrent according to the thickness of the AlGaN barrier layer when irradiated with 365 nm ultraviolet rays, and FIG. 11 (b) shows the photocurrent according to the gate applied voltage when irradiated with 365 nm ultraviolet rays.
12 shows gate voltage and time-dependent photoexcitation current curves of AlGaN/GaN phototransistors having AlGaN barrier layers of 10, 20, and 30 nm thickness when 365 nm light was injected.
FIG. 13 shows gate voltage and time-dependent photoexcitation current curves of AlGaN/GaN phototransistors having AlGaN barrier layers of 10, 20, and 30 nm thickness when 280 nm light is injected.

The photodetector of the present invention includes a substrate, a nucleation layer, a high resistance GaN layer, an Al _y Ga _1-y N channel layer, and an Al _x Ga _1-x N barrier layer, wherein the Al _x Ga ₁ -y N barrier layer is formed. A source electrode, a gate electrode, and a drain electrode are formed on the _xN barrier layer, and x and y satisfy 0≤y<x, 0<x<1, and 0≤y<1.

The substrate may include at least one of sapphire, diamond, InP, AlGaN, LiAlO ₂ , InN, GaP, Ge, InAs, AlAs, SiO ₂ , Si, SiC, GaN, and GaAs.

The nucleation layer is a layer for minimizing defects due to a crystal lattice mismatch between the substrate and the GaN layer grown thereon, and may include gallium (Ga) or aluminum (Al), preferably GaN or AlN. can include

The high resistance GaN layer is a heavily doped GaN layer. The high resistance GaN layer is a layer doped with carbon (C), iron (Fe) or magnesium (Mg). Metal Organic Chemical Vapor Deposition (MOCVD), Molecular Beam Epitaxy (MBE), Hydride Vapor Phase Epitaxy (HVPE), Plasma Enhanced Chemical It may be formed by any one of vapor deposition (PECVD), sputtering, and atomic layer deposition (ALD).

The Al _y Ga _1-y N channel layer (0≤y<1) may include a 2-dimension electron gas (2DEG) channel or a 2-dimensional hole gas (2DHG) channel. The Al _y Ga _1-y N channel layer may be formed by any one of metal-organic chemical vapor deposition, molecular beam epitaxy, hydride vapor deposition, plasma chemical vapor deposition, sputtering, and atomic layer deposition. In this specification, the Al _y Ga _1-y N channel layer may be simply referred to as a GaN channel layer.

The Al _x Ga _1-x N barrier layer (0<x<1) allows a 2DEG channel or a 2DHG channel to be formed in the Al _y Ga _1-y N channel layer, and may be n-doped n-type or p-doped p-type there is. The Al _x Ga _1-x N barrier layer may be formed by any one of metal-organic chemical vapor deposition, molecular beam epitaxy, hydride vapor phase epitaxy, plasma chemical vapor deposition, sputtering, and atomic layer deposition. The Al _x Ga _1-x N barrier layer may be 15 nm or less, preferably 10 nm or less, more preferably 5 nm or less. In this specification, the Al _x Ga _1-x N barrier layer may simply be referred to as an AlGaN barrier layer.

The source electrode, gate electrode, and drain electrode may include at least one of Co, Ir, Ta, Cr, Mn, Mo, Tc, W, Re, Fe, Sc, Ti, Sn, Ge, Sb, Al, Pt, Ni, and Au can include The source electrode, gate electrode and drain electrode may be formed by an electron beam evaporator.

In this specification, the photoexcitation current means a current generated by the photoelectric effect, and a current value between the source electrode and the drain electrode before applying light to a current value between the source electrode and the drain electrode appearing after applying light. can be expressed as a difference in In this specification, a photo excitation current is sometimes referred to as a photo-current.

Hereinafter, preferred embodiments of the present invention will be described in detail with reference to the accompanying drawings.

Preparation Example 1

An AlGaN/GaN heterojunction structure was formed by metal-organic chemical vapor deposition on a 4-inch c-plane (0001) sapphire substrate. Trimethylgallium and trimethylaluminum were used as Group 3 precursors, and ammonia (NH ₃ ) was used as a source of nitrogen. The epitaxial structure is a high-resistance GaN layer, a GaN channel layer, and an n-type AlGaN barrier layer is formed. After growing a GaN nucleation layer with a thickness of 30 nm on the substrate at 480 ° C, a high resistance GaN layer with a thickness of 2.0 μm is grown at 1000 ° C. Since carbon contributes to the compensation of free carriers, a high-resistance GaN layer can be achieved by carbon incorporation. Then, considering the 2DEG characteristics and wafer uniformity, a 150 nm thick GaN channel layer was grown at a high crystalline level. Finally, the n-type with an Al composition ratio of 30 mol% An AlGaN barrier layer was grown on the GaN channel layer. In order to investigate the characteristics of the AlGaN barrier layer according to its thickness, it was grown to a thickness of 10, 20 and 30 nm. The grown epitaxial wafer was fabricated with a Hall bar structure and HEMT for electrical evaluation. All patterns were formed by optical lithography, and mesa isolation was performed by inductively coupled plasma of a BCl ₃ /Cl ₂ gas mixture. The source electrode and the drain electrode were formed of a metal stack of Ti/Al/Ni/Au (20/100/25/50 nm) by electron beam evaporation and heat treated in a N ₂ environment at 850°C. The distance between the source electrode and the drain electrode was 8.0 μm, and the gate electrode having a length of 2.0 μm was formed of a Ni/Au (30/270 nm) metal stack.

Example 1: Evaluation of 2DEG Density and Electron Mobility According to the Thickness of Al _x Ga _1-x N Barrier Layer

In order to improve photoreactivity, first, the 2DEG density according to the thickness of the Al _x Ga _1-x N barrier layer was evaluated. For evaluation, as shown in FIG. 4 , an AlGaN/GaN heterojunction photodetector having an Al _x Ga _1-x N barrier layer having a thickness of 10, 20, or 30 nm was fabricated. For each photodetector, 2DEG density and electron mobility according to the thickness of the Al _x Ga _1-x N barrier layer were measured and shown in FIG. 5 .

As shown in FIG. 5, as the thickness of the Al _x Ga _1-x N barrier layer increased, a high-density two-dimensional electron gas channel was formed, and it was confirmed that the number of electrons in the channel increased. In particular, it was confirmed that a very high-density two-dimensional electron gas channel of 1.3×10 ¹³ /cm ² or more was formed at 20 nm or more. This seems to increase linearly as the thickness of the Al _x Ga _1-x N barrier layer increases due to the band bending due to the piezoelectric phenomenon at the AlGaN/GaN interface. However, it was confirmed that the electron mobility decreased with the increase in the thickness of the Al _x Ga _1-x N barrier layer due to electron scattering caused by the increase in electron density. This indicates that the AlGaN/GaN heterojunction structure having an Al _x Ga _1-x N barrier layer of 20 nm or more can be used as a high electron mobility transistor.

Example 2: Analysis of light absorption according to the thickness of Al _x Ga _1-x N barrier layer

In the AlGaN/GaN heterojunction structure, the voltage-current curves in the source and drain electrodes were confirmed with and without external light injection according to the thickness of the Al _x Ga _1-x N barrier layer. It is known that the GaN layer has a bandgap energy of about 3.4eV and absorbs light at about 365nm, and the AlGaN thin film has a bandgap energy of about 4.42eV and absorbs light at about 280nm. Therefore, in order to compare and analyze the light absorption generated in the AlGaN thin film and the light absorption generated in the GaN thin film, the photocurrent for 280 and 365 nm ultraviolet rays was confirmed in the Al _x Ga _1-x N barrier layer with a thickness of 10, 20, and 30 nm. did The results are shown in FIG. 6 .

6 is a voltage-current curve before and after externally injecting ultraviolet rays. The x-axis is the voltage between the gate electrode and the source electrode (V _Drain-Source , V _DS ), and the y-axis is the current between the gate electrode and the source electrode (I _Drain-Source , I _DS ). In order to compare and analyze the photocurrents absorbed and formed in the GaN thin film and the AlGaN thin film, ultraviolet rays of about 280 nm and 365 nm were injected. The voltage-current characteristics before UV injection from the outside are shown as empty triangles, circles, and squares in the graph, and after UV injection from the outside, the voltage-current characteristics are shown as filled triangles, circles, and squares in the graph. First, from the graph before injecting ultraviolet rays from the outside, the AlGaN/GaN device with a 10 nm thick Al _x Ga _1-x N barrier layer shows a very low voltage-current curve, and the Al _x Ga _1-x N barrier layer It was confirmed that as the thickness increased, a higher voltage-current curve was displayed. It seems that as the thickness of the Al _x Ga _1-x N barrier layer increases, the piezoelectric polarization characteristics of AlGaN and GaN become stronger, resulting in a higher density two-dimensional electron gas channel, resulting in a higher voltage-current curve. When 280 nm UV light was injected from the outside, it was confirmed that the current value increased near the pinch-off voltage, which is the point at which the current state is saturated between the drain electrode and the source electrode. It was confirmed that there was no difference. However, it can be seen that when 365 nm UV light is injected, the difference between voltage and current becomes larger than when 280 nm UV light is injected. That is, it was confirmed that the photoexcitation current increased when 365 nm UV was injected compared to when 280 nm UV was injected. As in the case of injecting 280 nm, it was confirmed that it has a higher photocurrent value than before injecting light near the pinch-off voltage. In particular, in the case of 10 nm thick AlGaN, when injecting 365 nm UV light from the outside It was confirmed that the excitation current rapidly increased. It is judged that the photoexcitation current greatly increased because the two-dimensional electron gas channel of the AlGaN/GaN heterostructure having a thin Al _x Ga _1-x N barrier layer of less than 10 nm is less than the photoexcitation carrier excited in the GaN layer.

In particular, when the voltage applied between the source and the drain is 3V, the photocurrent values according to the thickness of the Al _x Ga _1- xN barrier layer are changed to 10, 20, and 30 nm are shown in FIG. 7 . The left Y-axis represents the photocurrent value generated when 365 nm UV light is applied, and the right Y-axis represents the photocurrent value generated when 280 nm UV light is applied. The photoexcitation current was expressed as the value of the difference (I _photo -I _dark ) between the current value after light was applied and the current value before light was applied. When 280 nm UV light was injected from the outside, the value of the photoexcitation current increased from 0.07 A/mm to 0.14 A/mm as the thickness of the Al _x Ga _1-x N barrier layer increased from 10 nm to 30 nm. , the photoexcitation current decreased from 0.93 A/mm to 0.14 A/mm as the thickness of the Al _x Ga _1-x N barrier layer increased from 10 nm to 30 nm. In particular, when 365 nm ultraviolet light was applied, it was confirmed that the value of the photoexcitation current was about 13.3 times higher as the thickness of the Al _x Ga _1-x N barrier layer decreased from 30 nm to 10 nm. That is, the photodetector of the AlGaN/GaN heterojunction structure having an Al _x Ga _1-x N barrier layer having a thickness of 10 nm or less is 280 nm or more and 400 nm or less, preferably more than 280 nm and 365 nm or less, more preferably 300 nm or more and 365 nm or less, particularly It can be seen that it is preferable to detect light of 365 nm.

To analyze the relationship between electrons in the two-dimensional electron gas channel and photoexcited carriers formed by externally injected light, the number of photoelectrons formed by externally injected light and the thickness of Al _x Ga _1-x N barrier layer The number of electrons in the two-dimensional electron gas channel formed according to the method is calculated and shown in FIG. 8 .

8 shows the number of electrons formed by the two-dimensional electron gas channel according to the thickness of the Al _x Ga _1-x N barrier layer of 10, 20, and 30 nm, and when light is injected from the outside at an intensity of 280 μW, The number of electrons is indicated by a dotted line. As the thickness of the Al _x Ga _1-x N barrier layer increases, a strong two-dimensional electron gas channel is formed, indicating a larger number of electrons. When light is injected from the outside at an intensity of 280 μW, the number of electrons formed is about 1.3 × 10 ¹⁷ . It can be confirmed that this is similar to the number of electrons in the two-dimensional electron gas channel formed at the interface between AlGaN and GaN when the thickness of the Al _x Ga _1-x N barrier layer is about 15 nm. Therefore, if the thickness of AlGaN is too thick, the photoreactivity is small because the number of electrons in the two-dimensional electron gas channel is greater than the number of photoelectrons formed when light is injected from the outside, but when the thickness of AlGaN is less than 15 nm, especially the thickness of AlGaN When is 10 nm, since the number of photo-excited electrons formed by light injected from the outside is greater than the number of electrons in the two-dimensional electron gas channel, it seems to exhibit higher photoreactivity characteristics.

Example 3: Evaluation of light reactivity according to the wavelength of injected light

In order to confirm the light absorption at other wavelengths in addition to the specific absorption wavelength, the light reactivity according to the wavelength was evaluated and shown in FIG.

9 is a light response curve for light from 240 nm to 420 nm in AlGaN/GaN high electron mobility transistor devices having 10, 20, and 30 nm Al _x Ga _1-x N barrier layers. For the thicknesses of 10, 20, and 30 nm of the Al _x Ga _1-x N barrier layer, the light responsivity rapidly dropped at an injection wavelength of about 360 nm, and no significant change was observed around 300 nm. In the injection wavelength range before 380 nm, the photoreactivity decreased as the thickness of the Al _x Ga _1-x N barrier layer increased to 10, 20, and 30 nm. In particular, when the thickness of the Al _x Ga _1-x N barrier layer was 10 nm, it was confirmed that the light response had a very high value of about 1.44 x 10 ⁶ A/W. At the band gap of GaN thin film of about 3.4 eV, that is, about 360 nm, the photoresponse dropped sharply for the thicknesses of 10, 20, and 30 nm of the Al _x Ga _1-x N barrier layer, and most of the light absorption was in the GaN channel layer. indicates that it is present.

Example 4: Voltage-current curve according to gate voltage

Previously, we confirmed the change in light responsivity according to the thickness of the Al _x Ga _1-x N barrier layer in the AlGaN/GaN phototransistor structure. As a result, it was confirmed that the photoresponse was greatest at the thin barrier thickness of 10nm, which is because the density of the two-dimensional electron gas channel formed at the AlGaN/GaN interface is less than the photoexcitation current formed by light injected from the outside. judged Accordingly, we confirmed the change in photoreactivity by using the gate electrode of the two-dimensional electron gas channel formed according to the thickness of the Al _x Ga _1-x N barrier layer in the AlGaN/GaN phototransistor structure. Accordingly, a voltage-current curve was confirmed and shown in FIG. 10 when an ultraviolet wavelength of 365 nm having a high light reactivity was injected while externally applying from -1.0V to +1.0V to the gate electrode. In (a) to (c) of FIG. 10 , the graphs indicated by empty lines show results before light is injected from the outside, and the graphs indicated by filled lines show results after light is injected from the outside. is shown. Before light is injected from the outside, as the externally injected gate voltage increases from -1.0V to +1.0V regardless of the thickness of the AlGaN barrier layer, the current between the source and drain electrodes (I _Drain-Source , I _DS ) was confirmed to increase. This shows the behavior of a general transistor in which the amount of charge applied from the outside increases as the gate voltage increases, and the value of the current between the source and drain electrodes also improves. As this device was irradiated with 365 nm UV light, all of them showed higher current values regardless of the thickness of the AlGaN barrier layer. In particular, it was confirmed that the photocurrent due to photoexcitation increased by UV irradiation exhibited the highest photoexcitation current characteristic in the AlGaN barrier layer having a thickness of 10 nm.

11 shows a photocurrent curve (a) according to the AlGaN barrier layer thickness and a photocurrent curve (b) according to the gate applied voltage when irradiated with 365 nm ultraviolet rays. From the two curves, it was confirmed that the lower the applied gate voltage and the thinner the thickness of the AlGaN barrier layer, the higher the photoexcitation current characteristics. This is because the lower the externally applied voltage, especially the negative applied voltage, reduces the carriers in the channel and the current level of the phototransistor decreases, so that the photo-excited carriers formed by externally injecting ultraviolet light increase the current in the channel. It seems to be because it was formed higher enough to be able to control. Accordingly, in the AlGaN/GaN heterojunction structure phototransistor, as the thickness of the AlGaN barrier layer decreased, a higher photoexcitation current could be obtained, and as the gate voltage was lowered to a negative value, the photoexcitation current could be increased.

Example 5: Evaluation of photoexcitation current over time

12 shows gate voltage and time-dependent photoexcitation current curves of AlGaN/GaN phototransistors having AlGaN barrier layers of 10, 20, and 30 nm thickness when 365 nm light was injected. The photoresponse was shown when a gate voltage of -1.0V was applied from 0 seconds to 120 seconds, a gate voltage of 0V was applied from 120 seconds to 240 seconds, and a gate voltage +1.0V was applied from 240 seconds to 360 seconds. It can be seen that all three samples show good response to UV light over time. However, the thinner the AlGaN barrier layer, the faster the UV response rate and the higher photoexcitation current. In addition, when the thickness of the AlGaN barrier layer was 10 nm, the photoexcitation current increased when a gate voltage of - was applied, and the photoexcitation current decreased when + was applied. That is, when the thickness of the AlGaN barrier layer is 10 nm, the photoexcitation current can be amplified or reduced according to the application of the gate voltage.

Meanwhile, FIG. 13 shows gate voltage and time-dependent photoexcitation current curves of AlGaN/GaN phototransistors having 10, 20, and 30 nm thick AlGaN barrier layers when 280 nm light is injected. When the thickness of the AlGaN barrier layer was 10 nm, it was confirmed that the photoexcitation current did not change significantly depending on the gate voltage.

That is, it was confirmed from FIGS. 12 and 13 that when the wavelength of the injected light is 365 nm and the thickness of the AlGaN barrier layer is 10 nm, the photoexcitation current can be amplified or reduced according to the application of the gate voltage.

From the results of Examples 1 to 5 regarding the photodetector using the n-type AlGaN barrier layer, in the case of the photodetector using the p-type AlGaN barrier layer, when the applied gate voltage is a positive voltage, the photoexcitation current increases. it can be seen that

Claims (8)

Board;
an Al _y Ga _1-y N channel layer present on top of the substrate; and
An n-type Al _x Ga _1-x N barrier layer present on top of the channel layer,
A gate electrode, a source electrode, and a drain electrode are formed on the n-type Al _x Ga _1-x N barrier layer, and the gate electrode is disposed between the source electrode and the drain electrode,
y of the Al _y Ga _1-y N channel layer and x of the n-type Al _x Ga _1-x N barrier layer satisfy 0≤y<x, 0<x<1 and 0≤y<1,
An optical excitation current increases or decreases according to a gate voltage applied to the gate electrode;
When the applied gate voltage is a negative voltage, the photoexcitation current increases;
The n-type Al _x Ga _1-x N barrier layer has a thickness of 15 nm or less and detects light having a wavelength of 365 nm. delete delete delete Board;
an Al _y Ga _1-y N channel layer present on top of the substrate; and
A p-type Al _x Ga _1-x N barrier layer present on top of the channel layer,
A gate electrode, a source electrode, and a drain electrode are formed on the p-type Al _x Ga _1-x N barrier layer, and the gate electrode is disposed between the source electrode and the drain electrode,
y of the Al _y Ga _1-y N channel layer and x of the p-type Al _x Ga _1-x N barrier layer satisfy 0≤y<x, 0<x<1 and 0≤y<1,
An optical excitation current increases or decreases according to a gate voltage applied to the gate electrode;
When the applied gate voltage is a positive voltage, the photoexcitation current increases;
The p-type Al _x Ga _1-x N barrier layer has a thickness of 15 nm or less and detects light having a wavelength of 365 nm.



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