KR20180086667A - Photon detector with quantum well structure - Google Patents

Abstract

The present invention relates to a photon detector employing a quantum well structure. According to the present invention, the photon detector comprises: a substrate including n + InP; a buffer layer formed on the substrate; an absorption layer formed on the buffer layer and including InGaAs; a charge layer formed on the absorption layer and including the n + InP; a multiplication layer formed on the charge layer; and a diffusion layer formed on the multiplication layer and including p + InP. Therefore, since the photon detector can absorb light even in a quantum well layer of the multiplication layer, the photon detector can reduce a tunneling phenomenon by reducing a thickness of the existing absorption layer, and can achieve high photocurrent and low dark current.

Description

[0001] PHOTON DETECTOR WITH QUANTUM WELL STRUCTURE [0002]

The present invention relates to a photon detector, and more particularly to a photon detector employing a quantum well structure.

The PIN avalanche photodiode inserts the I region between the PN junctions and applies a large reverse voltage to produce an avalanche effect. When a large reverse voltage is applied to a PIN avalanche photodiode, electrons generated by light absorption are accelerated by a high electric field in the I region, colliding with other electrons confined in the atoms, losing energy and releasing electrons from the atoms It is ionized.

That is, an electron-hole pair is generated while exciting the electrons of the balanced band to the conduction band. The generated electrons and holes are separated and accelerated by the electric field and repeatedly ionized while hitting other electrons. The carrier exponentially increases and produces a large current, which is called the avalanche effect.

If a large reverse voltage is applied to obtain a high current gain due to the avalanche effect, the band is bent so that the energy value of the balanced band and the conduction band becomes equal to each other in the I region. When the band is increased, There is a probability that the electrons will pass through the forbidden band region and move to the conductive band. This phenomenon is called tunneling effect.

In the case of a photodiode, even when there is no incident light, the current due to the tunneling effect can be amplified by the avalanche effect to allow a large current to flow. This phenomenon increases the dark current and lowers the reliability of photodetection.

Therefore, a photodiode capable of suppressing the tunneling effect while using the avalanche effect is required for efficient optical detection.

Korean Patent Publication No. 10-0375829

Accordingly, a problem to be solved by the present invention is to provide a photon detector capable of suppressing the tunneling effect while using the avalanche effect.

According to an exemplary embodiment of the present invention, there is provided a photodetector including a substrate, an absorption layer, a charge layer, a multiplication layer, and a diffusion layer. The substrate includes n + InP. The absorber layer is formed on the substrate and includes InGaAs. The charge layer is formed on the absorber layer and includes n + InP. The multiplication layer is formed on the charge layer. The diffusion layer is formed on the growth layer and includes p + InP. The multiplication layer includes a lower barrier layer, a top barrier layer, and a multi-layer quantum well layer. The lower and upper barrier layers include n InP. The quantum well layer is formed between the lower barrier layer and the upper barrier layer and is composed of a GaAs well and an InP barrier.

For example, the multiplication layer may have a thickness of 0.29 um or less.

For example, the absorbent layer may have a thickness of 0.3 um.

The photon detector may further include a grading layer formed between the absorption layer and the charge layer.

At this time, the grading layer may include In _1-x Ga _x As _y P _1-y (0 <x <1, 0 <y <1).

The photon detector may further include a buffer layer including n InP between the substrate and the absorber layer.

As described above, the photon detector according to the present invention adopts a quantum well structure and can absorb light even in the quantum well of the multiplication layer, so that the thickness of the conventional absorption layer can be reduced.

In addition, by reducing the thickness of the absorber layer, it is possible to reduce the occurrence of band-to-band tunneling (BBT) at a high bias and to obtain a high photocurrent and a low dark current.

1 is a schematic cross-sectional view showing a laminated structure of a photon detector according to an exemplary embodiment of the present invention.
2 is a graph showing a result of calculating the quantum well energy level of InGaAs / InP of 8.2 nm at 300K.
3 is a graph simulating IV curves of a photon detector of the present invention and a prior art bulk photon detector using Silvaco TCAD.

The present invention is capable of various modifications and various forms, and specific embodiments are illustrated in the drawings and described in detail in the text. It should be understood, however, that the invention is not intended to be limited to the particular forms disclosed, but includes all modifications, equivalents, and alternatives falling within the spirit and scope of the invention. Like reference numerals are used for like elements in describing each drawing. In the accompanying drawings, the dimensions of the structures may be exaggerated to illustrate the present invention.

The terms first, second, etc. may be used to describe various components, but the components should not be limited by the terms. The terms are used only for the purpose of distinguishing one component from another. For example, without departing from the scope of the present invention, the first component may be referred to as a second component, and similarly, the second component may also be referred to as a first component.

The terminology used herein is for the purpose of describing particular embodiments only and is not intended to be limiting of the invention. The singular expressions include plural expressions unless the context clearly dictates otherwise. In the present application, the terms "comprising" or "having ", and the like, are intended to specify the presence of stated features, integers, steps, operations, elements, parts, or combinations thereof, But do not preclude the presence or addition of one or more other features, integers, steps, operations, elements, parts, or combinations thereof. In addition, A and B are 'connected' and 'coupled', meaning that A and B are directly connected or combined, and other component C is included between A and B, and A and B are connected or combined .

Unless defined otherwise, all terms used herein, including technical or scientific terms, have the same meaning as commonly understood by one of ordinary skill in the art to which this invention belongs. Terms such as those defined in commonly used dictionaries are to be interpreted as having a meaning consistent with the contextual meaning of the related art and are to be interpreted as either ideal or overly formal in the sense of the present application Do not. Also, in the claims of a method invention, each step may be reversed in order, unless the steps are clearly constrained in order.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS Reference will now be made in detail to the preferred embodiments of the present invention, examples of which are illustrated in the accompanying drawings.

1 is a schematic cross-sectional view showing a laminated structure of a photon detector according to an exemplary embodiment of the present invention.

The photon detector includes a substrate 100 including n + InP, a buffer layer 200 formed on the substrate 100, an absorber layer 300 formed on the buffer layer 200 and containing InGaAs, 300 and a diffusion layer 600 formed on the charge layer 500 and a diffusion layer 600 formed on the growth layer 600 and including p + InP, (700).

The absorption layer contains InGaAs, which absorbs light with a wavelength of 1.55 nm to form free electrons and holes.

The free electrons and holes formed in the absorber layer 300 move according to a high reverse voltage applied to the photon detector to obtain an avalanche effect and are accelerated by an electric field and impinge on other electrons to obtain a large current gain . The thickness of the InGaAs absorption layer 300 may be 0.3 um. In the photon detector of the present invention, the absorbing layer 300 may be reduced from 0.8 μm to 0.3 μm to obtain a higher photocurrent and a lower dark current.

The n &lt; + &gt; InP charge layer 500 formed on the absorber layer 300 has a function of significantly reducing the electric field to prevent a problem of increasing dark current due to a tunneling effect due to a high reverse voltage applied to the photon detector And is formed in a region between the absorption layer 300 and the multiplication layer 600 by n-doping at a concentration of 10 ¹⁶ cm ^-1 .

Meanwhile, a grading layer 400 may be formed between the absorption layer 300 and the charge layer 500. Since InGaAs and InP have a large energy bandgap difference, a potential barrier is generated in the bonding layer 300 and the charge layer 500, so that the holes can not pass over and accumulate, and the accumulated holes meet the electrons In order to prevent this phenomenon from being contributed to the current flow while being recombined, it is preferable to use the In _{1 - x} Ga _x As _y P _{1 - y} compound having a medium band gap of InP and InGaAs, The potential barrier can be reduced. The band gap size of the grading layer 400 can be controlled according to the ratio of x and y of InGaAsP.

The multiplication layer 600 is formed on the charge layer 500. The multiplication layer 600 has a doping concentration of 10 ¹⁵ cm ^-1 to maintain a large electric field to apply a reverse voltage to the carrier to maintain the multiplication efficiency . Preferably, the thickness of the multiplication layer 600 may be formed to 0.29 um in order to have an optimal avalanche effect.

The growth layer 600 includes a lower barrier layer 610 and an upper barrier layer 620 including n InP and is formed between the lower barrier layer 610 and the upper barrier layer 620 Layer quantum well layer 630, which may be a multi-layer quantum well layer.

The quantum well layer of the multi-layer is a layer arranged to form the shape of the potential barrier into a one-dimensional rectangular well.

When electrons are trapped in a narrow space surrounded by a high potential barrier like a well, various quantum effects such as quantization of the energy level of electrons are produced. In the quantum well structure, a quantized energy level is formed in the balance band and the conduction band. When light corresponding to the quantized energy level difference is incident, the electrons receive energy and transfer.

In the quantum well layer 630, the electron-hole pairs generated by the light must escape out of the quantum well in order to be a carrier contributing to the current flow. The carriers bound to the well may receive energy by light or heat, You can escape.

That is, by forming the quantum well layer 630 of multiple layers in the growth layer 600 using this principle, the carrier generation rate is increased. To this end, a material having an appropriate absorption coefficient at the wavelength of the incident light is determined, 300) It may be important to set the thickness of the material.

The quantum well layer 630 may be formed of a GaAs well 634 and an InP barrier 632 and the GaAs well 634 and the InP barrier 632 of the quantum well layer 630 may have the same thickness and / Can have the same doping concentration. Preferably, the GaAs well 634 may be an InGaAs well 634.

The energy level err of the quantum well can be calculated by the following equation (1).

(1)

(One)

Where m _w is the electron effective mass in the well, m _b is the electron effective mass at the barrier, L is the well width, V ₀ is the potential barrier potential of the quantum well, and k is the wave number.

The value of err becomes smaller as k (L / 2) becomes larger, becomes 0 at one point before π / 2, and increases again. Therefore, the k value can be obtained through the k (L / 2) value before the err value increases and the energy level can be calculated.

FIG. 2 is a graph showing a result of calculating the quantum well layer energy level of InGaAs / InP of 8.2 nm at 300 K. FIG.

For the effective amount of carriers and the energy bandgap, the values in Table 1 were used and ΔE _c = 0.41ΔE _g eV, ΔE _v = 0.59ΔE _g eV, and ΔE _g = 0.603 eV.

m _e * / m ₀ * m _hh * / m ₀ * m _lh * / m 0 * Eg (eV) InP (barrier) 0.077 0.600 0.120 1.344 InGaAs (well) 0.033 0.292 0.041 0.741

In FIG. 2, since the energy level difference between the hole and electron in the heavy mass is 0.80866 eV and the size corresponds to the light with the wavelength of 1532 nm, the absorption coefficient in the quantum well layer 630 is calculated based on the calculated energy level It can be seen that the designed quantum well layer 630 is suitable for absorbing light of 1.55 um. Preferably, when an electric field due to the reverse voltage is applied, the energy level shifts and the difference between the energy level of the balanced band well and the energy level of the conduction band well becomes small, so that it can be designed with a margin.

That is, the absorption layer 300, which has been designed to maintain a proper thickness in order to absorb light sufficiently by inserting the quantum well layer 630 of multiple layers capable of simultaneously multiplying the carrier and absorbing light into the growth layer 600, It is possible to reduce the physical section where the BBT occurs at a high bias.

The improvement effect when the quantum well structure is used for the growth layer 600 will be described in more detail with reference to the drawings.

Figure 3 is a graph simulating the I-V curve of a photon detector of the present invention and a prior art bulk photon detector using Silvaco TCAD.

3 (b), a conventional bulk photon detector causes a dark current and a photocurrent to yield at a bias of a similar magnitude. On the other hand, in FIG. 3 (a), it can be seen that the photocurrent detector of the present invention yields avalanche current at 21.55 V, which is lower than 22.80 V, which is a bias for causing the dark current to yield. This means that the photon detector of the present invention can detect a single photon with low dark current, as compared with the bulk photon detector.

While the present invention has been described in connection with what is presently considered to be practical and exemplary embodiments, it is to be understood that the invention is not limited to the disclosed embodiments, but, on the contrary, It will be understood by those skilled in the art that various changes in form and details may be made therein without departing from the spirit and scope of the invention as defined by the appended claims.

100: substrate 200: buffer layer
300: absorbing layer 400: grading layer
500: charge layer 600:
610: lower barrier layer 620: upper barrier layer
630: quantum well layer 700: diffusion layer

Claims (6)

a substrate comprising n + InP;
An absorption layer formed on the substrate and including InGaAs;
A charge layer formed on the absorber layer and including n + InP;
A multiplication layer formed on the charge layer; And
A diffusion layer formed on the multiplication layer and including p + InP;
/ RTI &gt;
The multi-
a lower barrier layer and an upper barrier layer comprising nInP; And
And a multi-layer quantum well layer formed between the lower barrier layer and the upper barrier layer and consisting of a GaAs well and an InP barrier.
The method according to claim 1,
Wherein the multiplication layer has a thickness of 0.29 um or less. The method according to claim 1,
Wherein the absorber layer has a thickness of 0.3 um. The method according to claim 1,
A grading layer formed between the absorption layer and the charge layer;
&Lt; / RTI &gt; further comprising a photodetector.
5. The method of claim 4,
Wherein the grading layer comprises In _{1 - x} Ga _x As _y P _{1 - y} (0 <x <1, 0 <y <1). The method according to claim 1,
A buffer layer including n InP between the substrate and the absorber layer;
&Lt; / RTI &gt; further comprising a photodetector.

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