TW202316642A - Photodiode which comprises a light-absorbing substrate, a first electrode portion, a second electrode portion, an anti-reflection layer, and a distributed Bragg reflection layer - Google Patents

Abstract

The present invention discloses a photodiode, which comprises: a light-absorbing substrate, a first electrode portion, a second electrode portion, an anti-reflection layer, and a distributed Bragg reflection layer. The anti-reflection layer is arranged to receive light entering the light-absorbing substrate, and the distributed Bragg reflection layer is arranged to reflect light passing through the light-absorbing substrate to be emitted from the light-absorbing substrate back into the light-absorbing substrate in order to increase the photo current and the spectral sensitivity of the photodiode. The light-absorbing substrate has a top surface and a bottom surface that are opposite to each other and the light-absorbing substrate includes a first semiconductor region, a second semiconductor region and a third region. The first semiconductor region and the semiconductor region are each in contact with the third region, and the first semiconductor region and the second semiconductor region are separated by the third region. The first semiconductor region and the second semiconductor region have opposite types of conductivity. The distributed Bragg reflection layer is formed by stacking multiple layers of dielectric materials. The anti-reflection layer is arranged on the top surface and in contact with the first semiconductor region, and the distributed Bragg reflection layer is arranged on the bottom surface and in contact with the second semiconductor region; or alternatively, the anti-reflection layer is arranged on the bottom surface and in contact with the second semiconductor region, and the distributed Bragg reflection layer is arranged on the top surface and in contact with the first semiconductor region.

Description

Photodiode

The invention relates to a light-receiving diode, in particular to a light-receiving diode with a distributed Bragg reflection layer on the surface.

A photodiode is a semiconductor device that converts light signals into electrical signals, and can be used in the detection of visible light, infrared light, and ultraviolet light. The receiver in some optical radar (LIDAR) systems uses light-receiving diodes to receive the light emitted by the system and reflected back when it hits the target, and converts it into an electrical signal for the system to transmit and receive from the light. Calculate the distance, depth or range of the target by using the time difference.

Some non-invasive blood oxygen concentration measuring instruments utilize red and infrared light sources and light-receiving diodes. Since oxygen-containing hemoglobin and oxygen-deficient hemoglobin have a large absorption rate difference for red light and infrared light, using red light and infrared light to penetrate skin tissue and blood vessels, and detecting changes in light intensity after reflection, it can be calculated blood oxygen concentration. Therefore, the sensitivity of light-receiving diodes to red light and infrared light bands is a key factor affecting the accuracy of blood oxygen concentration measurement.

When the light enters the light-receiving diode, the photon will be absorbed in the depletion region in the light-receiving diode, and the electron electrokinetic pair will be excited. These carriers will generate photocurrent after drifting and diffusing. However, part of the unabsorbed light will pass through the light-receiving diode and leave without generating a response. Due to the weak photocurrent and spectral sensitivity of conventional light-receiving diodes in the infrared light band, the effect when used to measure blood oxygen concentration is not satisfactory, and there is room for improvement.

Therefore, the inventor of the present invention conceived and designed a light-receiving diode to improve the deficiencies of the conventional technology and enhance industrial applicability.

In order to achieve the above-mentioned purpose, the technical means used in the present invention is to provide a light-receiving diode, including: a light-absorbing substrate, the light-absorbing substrate has a top surface and a bottom surface that are the back sides of each other, and the light-absorbing substrate has a A first semiconductor region, a second semiconductor region and a third region, the first semiconductor region and the second semiconductor region respectively contact the third region, the first semiconductor region and the second semiconductor region are formed by the third region Separated from each other, the first semiconductor region and the second semiconductor region have opposite conductivity types; an antireflection layer and a distributed Bragg reflection layer are formed by stacking multiple layers of dielectric material films; wherein the antireflection layer is disposed on the top surface and contacting the first semiconductor region, the distributed Bragg reflection layer is disposed on the bottom surface contacting the second semiconductor region, or the anti-reflection layer is disposed on the bottom surface and contacts the In the second semiconductor region, the distributed Bragg reflection layer is arranged on the top surface and contacts the first semiconductor region; wherein, the anti-reflection layer is arranged to receive a light entering the light-absorbing substrate, and the distributed Bragg reflection layer It is arranged to reflect back to the light-absorbing substrate the light passing through the light-absorbing substrate and intended to exit from the light-absorbing substrate.

In one embodiment of the light receiving diode of the present invention, the first semiconductor region is a p-type semiconductor, and the second semiconductor region is an n-type semiconductor.

In one embodiment of the light receiving diode of the present invention, the first semiconductor region is an n-type semiconductor, and the second semiconductor region is a p-type semiconductor.

In one embodiment of the light receiving diode of the present invention, the thickness of the distributed Bragg reflection layer is 2 μm to 30 μm

In one embodiment of the light receiving diode of the present invention, the anti-reflection layer contains silicon nitride.

In one embodiment of the light receiving diode of the present invention, the thickness of the distributed Bragg reflection layer is 3 μm.

The light-receiving diode of the present invention uses a distributed Bragg reflection layer to reflect light passing through the light-absorbing substrate to be emitted from the light-absorbing substrate back to the light-absorbing substrate, thereby reducing light loss and improving photocurrent and spectral sensitivity. In one embodiment, the thickness of the distributed Bragg reflective layer 4 is 2 μm to 30 μm, and for the infrared light band of 900 nm to 1000 nm, the reflectivity can reach 95% to 99%, which improves the performance of the light receiving diode for the infrared light band. The photocurrent and spectral sensitivity of the light-receiving diodes in the prior art are improved, and the photocurrent and spectral sensitivity of the light-receiving diodes in the infrared light band are weak, and the sensing performance of the light-receiving diodes (such as blood oxygen concentration detection) and availability.

The detailed description and technical content of the present invention are described below with the drawings. However, the attached drawings are only provided for reference and description to help understand the present invention, and are not intended to limit the scope of the present invention.

Please refer to Figure 1A to Figure 2B, the light receiving diode 100 includes: a light absorbing substrate 1, a first electrode part 21, a second electrode part 22, an anti-reflection layer 3 and a distributed Bragg reflection layer 4 .

The light-absorbing substrate 1 has a top surface S1 and a bottom surface S2 which are back sides of each other. The light absorbing substrate 1 has a first semiconductor region Rd1 , a second semiconductor region Rd2 and a third region Rin. The first semiconductor region Rd1 and the second semiconductor region Rd2 respectively contact the third region Rin, and the first semiconductor region Rd1 and the second semiconductor region Rd2 are separated by the third region Rin. In this embodiment, the light absorbing substrate 1 is a silicon substrate.

The first semiconductor region Rd1 and the second semiconductor region Rd2 are regions doped with higher concentration of impurities in the light-absorbing substrate 1 , and the third region Rin is a lightly doped region. The first semiconductor region Rd1 and the second semiconductor region Rd2 have opposite conductivity types, and are doped with impurities of opposite conductivity types. For example: the first semiconductor region Rd1 is doped with donor impurities (such as group VA elements of the periodic table) to become an n-type semiconductor, and the second semiconductor region Rd2 is doped with acceptor impurities (such as group IIIA elements of the periodic table) to become a p-type semiconductor . Alternatively, the second semiconductor region Rd2 is doped with donor impurities to become an n-type semiconductor, and the first semiconductor region Rd1 is doped with acceptor impurities to become a p-type semiconductor.

The first electrode part 21 is in contact with the first semiconductor region Rd1, and the second electrode part 22 is in contact with the second semiconductor region Rd2. The light receiving diode 100 can be connected to a circuit or receive an external voltage through the first electrode portion 21 and the second electrode portion 22 . The material of the first electrode portion 21 and the second electrode portion 22 can be a metal or an alloy suitable for forming ohmic contact and conducting electricity with the first semiconductor region Rd1 and the second semiconductor region Rd2 . The first electrode portion 21 and the second electrode portion 22 can be formed by vapor deposition, sputtering, electroplating, and the like. Each of the first electrode part 21 and the second electrode part 22 can be a continuous pattern. The first electrode portion 21 and the second electrode portion 22 can be disposed on the same side or different sides of the light absorbing substrate 1 . In the embodiment shown in the figures of the present invention, the first electrode portion 21 and the second electrode portion 22 are both disposed on the top surface S1. The second electrode portion 22 can contact the second semiconductor region Rd2 through a via (the via is not located in the section taken in the drawings of the present invention, and is not shown in the drawings).

The anti-reflection layer 3 and the distributed Bragg reflection layer 4 are respectively disposed on the top surface S1 or the bottom surface S2 , respectively contacting the first semiconductor region Rd1 or the second semiconductor region Rd2 . The light-receiving diode 100 uses the surface where the anti-reflection layer 3 is located as the light-receiving surface, and can be used to receive light from the front (top surface S1 ) or back (bottom surface S2 ) of the crystal grain (light-absorbing substrate 1 ). As shown in Figure 1A and Figure 2A, the anti-reflection layer 3 is disposed on the top surface S1 and contacts the first semiconductor region Rd1, and the distributed Bragg reflection layer 4 is disposed on the bottom surface S2 and contacts the first semiconductor region Rd1. contact the second semiconductor region Rd2. Also as shown in FIG. 1B and FIG. 2B, the anti-reflection layer 3 is disposed on the bottom surface S2 in contact with the second semiconductor region Rd2, and the distributed Bragg reflection layer 4 is disposed on the top surface S1 and contact the first semiconductor region Rd1.

As shown in FIG. 2A and FIG. 2B , the anti-reflection layer 3 is configured to receive a light L and make the light L enter the light-absorbing substrate 1 . When the light L passes through the anti-reflection layer 3 and enters the light-absorbing substrate 1 , a part (<1%) of the light Lr is reflected by the anti-reflection layer 3 . In this embodiment, the light L1 entering the light-absorbing substrate 1 will be absorbed in the light-absorbing region of the light-absorbing substrate 1 to generate photocurrent. The distributed Bragg reflection layer 4 is configured to reflect the light L2 that passes through the light-absorbing substrate 1 and intends to exit the light-absorbing substrate 1 back into the light-absorbing substrate 1 , that is, the light L2r. It should be noted that the light angles in the drawings are only for illustration, and are not drawn to scale according to the refractive index of the medium through which the light actually passes. Since the light L2r is reflected back to the light-absorbing substrate 1 to reduce light loss, the photocurrent and spectral sensitivity of the light-receiving diode 100 are improved.

The material of the anti-reflection layer 3 can be silicon nitride (SiNx), formed on the light-absorbing substrate 1 by plasma-assisted chemical vapor deposition (PECVD).

In this embodiment, a distributed Bragg reflector (distributed Bragg reflector) 4 is formed by stacking multiple layers of dielectric material films. In a preferred embodiment, the thickness of the distributed Bragg reflection layer 4 is 2 µm to 30 µm. The 3rd figure has shown the reflectivity of the light receiving diode 100 of an embodiment of the present invention for the light in the range of 300nm～1200nm wavelength, in this embodiment, the thickness of the distributed Bragg reflection layer 4 is 3 μm, for 900nm In the infrared band to 1000nm, the reflectivity can reach 95% to 99%, so the photocurrent and spectral sensitivity of the light receiving diode 100 for this band can be further improved.

The above description is only a preferred feasible embodiment of the present invention, and therefore does not limit the patent scope of the present invention. For example, all equivalent structural changes made by using the description and drawings of the present invention are all included in the scope of the present invention. .

10 0: light-receiving diode 1: light-absorbing substrate Rd1: first semiconductor region Rd2: second semiconductor region Rin: third region S1: top surface S2: bottom surface 21: first electrode portion 22: second electrode Part 3: Anti-reflective layer 4: Distributed Bragg reflective layer L: Light Lr: Light L1: Light L2: Light L2r: Light

FIG. 1A is a schematic diagram of an embodiment of a light-receiving diode of the present invention, wherein the anti-reflection layer is in contact with the first semiconductor region, and the distributed Bragg reflection layer is in contact with the second semiconductor region. Fig. 1B is a schematic diagram of another embodiment of the light-receiving diode of the present invention, wherein the anti-reflection layer is in contact with the second semiconductor region, and the distributed Bragg reflection layer is in contact with the first semiconductor region. Fig. 2A is a schematic diagram of the light receiving diode of the embodiment shown in Fig. 1A. Fig. 2B is a schematic diagram of the light receiving diode of the embodiment shown in Fig. 1B. Fig. 3 shows the reflectance of the light-receiving diode in the embodiment of the present invention for light with a wavelength in the range of 300nm-1200nm.

100: light receiving diode

1: Light absorbing substrate

Rd1: first semiconductor region

Rd2: second semiconductor region

Rin: the third area

S1: top side surface

S2: Bottom side surface

21: The first electrode part

22: Second electrode part

3: Anti-reflection layer

4: Distributed Bragg reflection layer

Claims (6)

A light-receiving diode, comprising: A light-absorbing substrate, the light-absorbing substrate has a top side surface and a bottom-side surface which are the back sides of each other, the light-absorbing substrate has a first semiconductor region, a second semiconductor region and a third region, the first semiconductor region respectively contacting the third region with the second semiconductor region, the first semiconductor region and the second semiconductor region are separated by the third region, the first semiconductor region and the second semiconductor region have opposite conductivity types; an anti-reflection layer; and A distributed Bragg reflection layer is formed by stacking multiple layers of dielectric material films; in, the antireflection layer is disposed on the top surface and contacts the first semiconductor region, the distributed Bragg reflection layer is disposed on the bottom surface and contacts the second semiconductor region, or, the anti-reflection layer is disposed on the bottom surface and contacts the second semiconductor region, and the distributed Bragg reflection layer is disposed on the top surface and contacts the first semiconductor region; in, The anti-reflection layer is configured to receive light entering the light-absorbing substrate, and the distributed Bragg reflection layer is configured to reflect light that passes through the light-absorbing substrate and intends to exit the light-absorbing substrate back to the light-absorbing substrate. The light-receiving diode according to claim 1, wherein the first semiconductor region is a p-type semiconductor, and the second semiconductor region is an n-type semiconductor. The light-receiving diode according to claim 1, wherein the first semiconductor region is an n-type semiconductor, and the second semiconductor region is a p-type semiconductor. The light-receiving diode as described in Claim 2 or 3, wherein the thickness of the distributed Bragg reflection layer is 2 µm to 30 µm. The light-receiving diode according to claim 2 or 3, wherein the anti-reflection layer contains silicon nitride. The light-receiving diode as described in Claim 4, wherein the thickness of the distributed Bragg reflection layer is 3 μm.

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