Photoelectric detector with inverted p-GaN / AlGaN / n-GaN structure

Abstract

A photoelectric detector with an inverted p-GaN / AlGaN / n-GaN structure is characterized in that a conventional p-GaN / AlGaN / n-GaN structure is inverted to form the inverted p-GaN / AlGaN / n-GaN structure, and the inverted p-GaN / AlGaN / n-GaN structure comprises an n-type GaN layer, namely, n-GaN, an Al < x > Ga < 1-x > N barrier layer and a p-type GaN layer, namely, p-GaN, which are sequentially stacked from top to bottom; according to the invention, the n-GaN is doped with the p-GaN, so that the ultraviolet light directly enters the n-GaN, the absorption or interference of the p-GaN and the passivation layer on the ultraviolet light in a conventional structure is avoided, the absorption efficiency of the ultraviolet light is improved, higher sensitivity and gain can be obtained, and meanwhile, due to high electron mobility and high saturation drift speed in the GaN, the detector has a very high response speed, so that the sensitivity and the gain of the detector are improved. And the detector is simple in process and low in cost, and can meet the requirements of the field of ultraviolet detection, especially the field of weak light detection.

Description

Technical Field

[0001] The present invention relates to the field of semiconductor device design and light detection technology, and in particular to a photodetector with an inverted p-GaN / AlGaN / n-GaN structure. Background Art

[0002] GaN devices based on the AlGaN / GaN structure can enhance the device's high-frequency, high-power, and low-noise performance by leveraging the high-density, high-mobility two-dimensional electron gas channel in their heterojunction structure, playing an important role in fields such as communications, power electronics, and aerospace. Among them, enhancement-mode devices based on the p-GaN / AlGaN / n-GaN structure play an important role in the field of photodetection. For example, patent application international publication number WO2008151138A1 discloses a p-GAN / ALGAN / ALN / GAN enhancement-mode field-effect transistor, comprising a p-type nitride layer between the gate and channel of the HEMT to reduce electron population under the gate. The HEMT may also include an aluminum nitride (AlN) layer between the HEMT's AlGaN layer and buffer layer to reduce the on-resistance of the channel. However, when this structure performs photoelectric detection, incident light must pass through the p-type GaN and passivation layers before reaching the sensitive area. These layers cause light intensity attenuation, reducing the device's absorption efficiency for incident light, which in turn reduces the device's signal strength and the detector's gain and sensitivity. Therefore, a new structure is needed to reduce the attenuation of incident light intensity, thereby improving device gain and sensitivity and meeting the needs of low-light detection scenarios in the field of photoelectric detection. Summary of the Invention

[0003] In order to overcome the above-mentioned defects of the prior art, the purpose of the present invention is to provide a photodetector with an inverted p-GaN / AlGaN / n-GaN structure. The p-GaN / AlGaN / n-GaN structure is inverted to allow ultraviolet light to be directly incident on the n-GaN, thereby preventing the ultraviolet light from being absorbed or interfered by the p-type GaN layer and the passivation layer when incident, thereby improving the device's absorption efficiency of ultraviolet light, thereby improving gain and sensitivity.

[0004] In order to achieve the above object, the technical solution adopted by the present invention is:

[0005] A photodetector with an inverted p-GaN / AlGaN / n-GaN structure, with a high-resistance silicon-based substrate 10 as the bottom, and a cathode array 9 and an anode array 8 respectively arranged on the left and right ends of the upper surface of the high-resistance silicon-based substrate 10;

[0006] An inverted p-GaN / AlGaN / n-GaN structure is set on the high-resistance silicon substrate 10, including n-type GaN layers, namely n-GaN6, AlGaN, and n-GaN layers stacked in sequence from top to bottom. xGa 1-x N barrier layer 5 and p-type GaN layer, i.e., p-GaN4;

[0007] Al x Ga 1-x The left and right ends of the lower surface of the N barrier layer 5 are the cathode 2 and anode 1 of the photodetector, and the cathode and anode are connected to the Al x Ga 1-x The N barrier layer 5 is in close contact, wherein the cathode 2 is also in close contact with the lower surface of the p-GaN 4, and the close contact is an ohmic contact; the anode 1 is connected to the anode array 8 through the solder ball 7; the cathode 2 is connected to the cathode array 9 through the solder ball 7;

[0008] Al x Ga 1-x The portion below the N barrier layer 5 and excluding the p-GaN 4 , the anode 1 , and the cathode 2 is filled with a silicon dioxide passivation layer 3 .

[0009] The p-GaN4 is p-type doped, with a doping concentration of 10 18 ~10 20 cm -3 , with a thickness of 50-10nm.

[0010] The Al x Ga 1-x The N barrier layer 5 is undoped; its thickness is 8 to 12 nm, and Al x Ga 1-x The Al composition x in the N barrier layer is 0.2 to 0.3.

[0011] The n-GaN6 is n-type doped, and the doping concentration is less than 10 16 cm -3 , with a thickness of 10-30nm.

[0012] The solder balls 7 are made of metal.

[0013] When in use, the cathode array 9 is grounded, and ultraviolet light is irradiated downward from above the n-GaN 6 perpendicular to the device surface. A voltage is connected to the anode array 8, and the anode array 8 outputs current.

[0014] Compared with the conventional p-GaN / AlGaN / n-GaN structure, the present invention has the following advantages:

[0015] The inverted p-GaN / AlGaN / n-GaN structure allows ultraviolet light to directly enter n-GaN, so that the ultraviolet light incident on n-GaN6 will not be attenuated by the passivation layer 3 or p-type GaN4, thereby improving the detector's absorption efficiency of ultraviolet light, increasing output sensitivity and current gain, and enabling the detector to meet the detection needs of low-light scenes. BRIEF DESCRIPTION OF THE DRAWINGS

[0016] Figure 1 Schematic diagram of a photodetector with an inverted p-GaN / AlGaN / n-GaN structure.

[0017] In the figure: 1-anode; 2-cathode; 3-silicon dioxide passivation layer; 4-p-GaN; 5-Al x Ga 1-x N barrier layer; 6-n-GaN; 7-solder ball; 8-anode array; 9-cathode array; 10-high-resistance silicon substrate. DETAILED DESCRIPTION

[0018] The technical solution of the present invention will be described in further detail below with reference to the accompanying drawings.

[0019] like Figure 1 As shown, a photodetector with an inverted p-GaN / AlGaN / n-GaN structure:

[0020] On a high-resistance silicon-based substrate 10, a cathode array 9 and an anode array 8 are respectively provided at the left and right ends of the surface;

[0021] An inverted p-GaN / AlGaN / n-GaN structure is set on the high-resistance silicon substrate 10. The inverted p-GaN / AlGaN / n-GaN basic structure is an n-type GaN layer, namely n-GaN6, Al x Ga 1-x The N barrier layer 5 and the p-type GaN layer, i.e., p-GaN4, are stacked in sequence from top to bottom;

[0022] The Al x Ga 1-x The left and right ends of the lower surface of the N barrier layer 5 are the cathode 2 and anode 1 of the photodetector (the formation of the cathode and anode is: on the Al x Ga 1-x A source and a drain are provided at the left and right ends of the lower surface of the N barrier layer 5, a gate is provided on the lower surface of the p-type GaN 4, the gate and the source are connected to form a cathode 2, and the drain is used as an anode 1). The anode 1 and the anode array 8, and the cathode 2 and the cathode array 9 are connected via solder balls 7;

[0023] In Al x Ga 1-x The portion below the N barrier layer 5 other than the p-type GaN 4 , the anode 1 and the cathode 2 is filled with a silicon dioxide passivation layer 3 .

[0024] Figure 1Shown are the cross-sectional details of the inverted p-GaN / AlGaN / n-GaN structure photodetector. The width of the inverted p-GaN / AlGaN / n-GaN structure photodetector perpendicular to the cross-section is 100μm, and multiple inverted p-GaN / AlGaN / n-GaN structures can be arranged perpendicular to the cross-sectional direction.

[0025] In the absence of light (dark field), p-GaN4 will deplete Al x Ga 1-x A two-dimensional electron gas channel is formed by polarization at the interface of the N barrier layer 5 / n-GaN6. When the device is in the off state and a voltage is applied between the anode array 8 and the cathode array 9, no output current is generated at the cathode array 8. When ultraviolet light of appropriate intensity is added, it is incident on the n-GaN6, generating electron-hole pairs in the n-GaN6, reducing the width of the space charge region. At the same time, a photovoltage is generated in the pn junction formed by the p-GaN4 and n-GaN6. Since the cathode contacts the p-GaN in the inverted p-GaN / AlGaN / n-GaN structure, the photovoltage regulates the electron concentration in the conductive channel. Under these two effects, an electron gas channel is formed, and by applying a voltage between the anode array 8 and the cathode array 9, an output current is generated.

[0026] The p-GaN4 is p-type doped, with a doping concentration of 10 18 cm -3 The p-GaN4 thickness is 70nm and the left and right widths are 6μm.

[0027] The Al x Ga 1-x The N barrier layer 5 is undoped; its thickness is 10 nm, and Al x Ga 1-x The Al composition x in the N barrier layer is 0.2.

[0028] The n-GaN layer 6 is n-type doped, with a doping concentration of 10 16 cm -3 , the thickness of the n-GaN layer 6 is 20 nm.

[0029] Al x Ga 1-x The width of the N barrier layer 5 and the n-GaN layer 6 are both 14 μm; the width of the p-GaN4 layer is 14 μm. x Ga 1-x The N barrier layer 5 is bilaterally symmetrical.

[0030] The anode 1 is an ohmic contact electrode, and the cathode 2 is connected to the Al x Ga 1-x The N barrier layer 5 is an ohmic contact, and forms an ohmic contact with the p-GaN 4 .

[0031] The solder balls 7 are made of metal and have good electrical conductivity, ensuring good contact between the cathode 2 and the cathode array 9 , and between the anode 1 and the anode array 8 .

[0032] The basic detection principle and process of the present invention are as follows:

[0033] Due to Al x Ga 1-x The piezoelectric polarization and spontaneous polarization of the N barrier layer 5 and the spontaneous polarization of n-GaN6, in Al x Ga 1-x A high concentration of two-dimensional electron gas is formed at the interface of the N barrier layer 5 / n-GaN6, with a density of the order of 10 13 cm -2 , the concentration is on the order of 10 19 cm -3 or higher. p-GaN4 will deplete the Al above it. x Ga 1-x The two-dimensional electron gas at the interface of the N barrier layer 5 / n-GaN6, because the doping concentration of p-type GaN is much greater than that of n-GaN, that is, the width of the depletion region is greater than the thickness of the n-GaN layer. In the absence of light, the part of the two-dimensional electron gas channel located above the p-type GaN is depleted. When a voltage is applied between the anode and cathode, the device does not conduct. In use:

[0034] (1) Ultraviolet light is irradiated downward from above n-GaN6 perpendicular to the upper surface of the detector. n-GaN6 absorbs ultraviolet light to generate electron-hole pairs, which will narrow the space charge region on p-GaN4.

[0035] (2) Since cathode 2 is in contact with p-GaN4, the photo-generated voltage generated by the pn junction formed by p-GaN4 and n-GaN6 will regulate the Al x Ga 1-x Electron concentration at the interface of N barrier layer 5 / n-GaN 6.

[0036] Under the above two effects, x Ga 1-x A conductive channel is formed at the interface of the N barrier layer 5 / n-GaN 6 , and by applying a voltage of 5V to the anode array 8 and the cathode array 9 , an output current can be generated on the anode array 8 .

[0037] In summary, the present invention is based on a conventional p-GaN / AlGaN / n-GaN structure. The inverted p-GaN / AlGaN / n-GaN structure, formed by inverting the conventional p-GaN / AlGaN / n-GaN structure, can achieve higher UV absorption efficiency, current gain, and sensitivity in a light field. Compared with the conventional p-GaN / AlGaN / n-GaN structure, the inverted p-GaN / AlGaN / n-GaN structure allows UV light to directly enter the n-GaN, avoiding UV light attenuation in the p-GaN and passivation layers, improving UV absorption efficiency, thereby generating greater current and gain, and achieving higher sensitivity and gain. At the same time, due to the high electron mobility and high saturation drift velocity in GaN, the detector has a very high response speed. The detector is simple to manufacture and low in cost, meeting the needs of the UV detection field.

Claims

1. A photodetector with an inverted p-GaN / AlGaN / n-GaN structure, with a high-resistance silicon-based substrate (10) as the bottom, and a cathode array (9) and an anode array (8) respectively arranged at the left and right ends of the upper surface of the high-resistance silicon-based substrate (10), characterized in that: An inverted p-GaN / AlGaN / n-GaN structure is arranged above a high-resistance silicon-based substrate (10), including n-type GaN layers, namely n-GaN (6), AlGaN (7), and n-GaN (8). x Ga 1-x N barrier layer (5) and p-type GaN layer, i.e., p-GaN (4); 3Al x Ga 1-x The left and right ends of the lower surface of the N barrier layer (5) are the cathode (2) and anode (1) of the photodetector, and the cathode and anode (2, 1) are connected to the Al x Ga 1-x The N barrier layer (5) is in close contact, wherein the cathode (2) is also in close contact with the lower surface of the p-GaN (4), and the close contact is an ohmic contact; the anode (1) is connected to the anode array (8) through a solder ball (7); and the cathode (2) is connected to the cathode array (9) through a solder ball (7); Al x Ga 1-x A silicon dioxide passivation layer (3) is filled below the N barrier layer (5) and outside the p-GaN (4), the anode (1) and the cathode (2).

2. The inverted p-GaN / AlGaN / n-GaN photodetector according to claim 1, characterized in that: The p-GaN (4) is p-type doped, with a doping concentration of 10 18 ~10 20 cm -3 , with a thickness of 50-100nm.

3. The inverted p-GaN / AlGaN / n-GaN photodetector according to claim 1, characterized in that: The Al x Ga 1-x The N barrier layer (5) is undoped and has a thickness of 8 to 12 nm. x Ga 1-x The Al composition x in the N barrier layer is 0.2 to 0.

3.

4. The inverted p-GaN / AlGaN / n-GaN photodetector according to claim 1, wherein: The n-GaN (6) is n-type doped, and the doping concentration is less than 10 16 cm -3 , with a thickness of 10-30nm.

5. The inverted p-GaN / AlGaN / n-GaN photodetector according to claim 1, characterized in that: The solder ball (7) is made of metal.

6. The inverted p-GaN / AlGaN / n-GaN photodetector according to claim 1, characterized in that: When in use, the cathode array (9) is grounded, and ultraviolet light is irradiated downward from above the n-GaN (6) perpendicularly to the device surface. A voltage is connected to the anode array (8), and the anode array (8) outputs current.

Images