JPH02148770A - Photodiode - Google Patents

Abstract

PURPOSE:To detect the variations in the wavelength and intensity of a light by providing a multiple quantum well structure having an absorption end coincident with the wavelength of a light to be detected at the light incident side to a light absorption layer in a semiconductor laminated structure. CONSTITUTION:A crystalline layer 12, a light absorption layer 13, a crystalline layer 14 and 15 are piled on a semiconductor substrate 11. A multiple quantum well structure 16 is provided at the center of the layer 15, and a crystalline layer 17 is piled on the upper surface of the structure 16. In this photodiode, when a light having predetermined energy is radiated, an electromotive force is generated in the laminated structure. Accordingly, when a reverse bias voltage is applied through a P-type electrode 23 and an N-type electrode 24, a photocurrent flows reversely. In this case, when the applied voltage is varied, e.g., when a voltage is applied or not applied to the structure 16 through the electrodes 20, 23, the structure 16 may be used as a filter having a different function. Thus, variation in the wavelength can be detected, and the variation in the intensity of the light can be also detected.

Description

DETAILED DESCRIPTION OF THE INVENTION Field of Industrial Application J The present invention relates to a photodiode used in technical fields such as optical communications.

rPrior Art J A typical example of a photodiode is shown in FIG.

The photodiode in FIG. 5 has an n-InP layer 2, an n-Ga1nAs light absorption layer 3, an n-InP layer 2, an n-Ga1nAs light absorption layer 3,
A P-InP layer 4 and a P'Ga1nAs layer 5 are laminated, and an anti-irradiation film 6 and a P-side electrode 7 are provided on the P'GaInAs layer 5 side, and an N-side electrode is provided on the n'InP substrate 1 side. 8 are provided respectively.

When the above photodiode is irradiated with light with energy larger than the band gap from the direction of the arrow in Figure 5, electrons are excited from the valence band to the conduction band within the semiconductor stacked structure, and electrons and positive A hole pair occurs, and
The electrons and holes thus generated are pushed to the NFI and P regions by the potential barrier of the pn junction, respectively, so that an electromotive force is generated in the photodiode.

At this time, if a reverse bias voltage is applied to the pn junction via the picture electrodes 7 and 8, a photocurrent flows in the opposite direction.

FIG. 6 shows the relationship between the absorption edge wave input C of the light absorption layer 3 and the detected (measured) wavelength input 0 in the photodiode of FIG.

Generally, in the case of a fort diode, it is used under the condition that λo is less than C for the blue wavelength, so that changes in the intensity of incident light can be detected.

``Problems to be Solved by the Invention J'' By the way, in light emitting devices such as semiconductor lasers, it is important not only to stabilize the oscillation wavelength, but also to detect the wavelength.

However, in the case of the photodiode illustrated in FIG.
Changes in light intensity can be detected, but changes in wavelength cannot be detected.
This cannot be detected and the above requirements cannot be met.

In view of these problems, the present invention seeks to provide a photodiode that can detect not only changes in the intensity of light but also changes in its wavelength.

1. In order to achieve the intended purpose, the specified invention (Claim 1) includes a semiconductor laminated structure including a light absorption layer formed on a laminated surface of a semiconductor substrate. In a photodiode in which a P-side electrode and an N-side electrode are provided outside a substrate and a semiconductor laminated structure, on the light incidence side of the light absorption layer in the semiconductor laminated structure, a light wavelength that mutually matches the light wavelength to be detected is provided. It is characterized by having a multiple quantum well structure with an absorption edge.

Furthermore, in the case of the related invention (Claim 2), in the photodiode of the specified invention (Claim 1), the multiple quantum well structure is provided with electrodes for independently applying an electric field thereto. Features.

r Effect J In the case of the photodiode according to the specified invention, the absorption edges of the multiple quantum well structure provided on the light incidence side of the light absorption layer mutually match the wavelength of light to be detected, so that the photodiode has A change in wavelength of incident light incident from a predetermined direction can be detected as a change in photocurrent.

In the case of the photodiode according to the related invention, the multiple quantum well structure is provided with electrodes for independently applying an electric field.

The function when such an electrode is not used is the same as above, but when an electric field is applied to the multi-quantum well structure through the electrode, only the change in the intensity of incident light can be detected as a photocurrent.

Therefore, in the case of the photodiode according to the related invention,
Changes in incident light can be detected as changes in photocurrent, or only changes in the intensity of the incident light can be detected as photocurrent.

rExample J Hereinafter, regarding an example of a photodiode according to the present invention,
This will be explained with reference to the drawings.

In FIG. 1, on a semiconductor substrate 11 made of n-InP, there are a crystal layer 12 made of n-1nP, a crystal layer 12 made of n-GaIn
A crystal layer (=light absorption layer) 13 made of As, a crystal layer 14 made of P''InP, a crystal layer 1 made of P-Ga1nAs.
5 is formed in 11 layers.

On the crystal layer 15, a multiple quantum well structure (MQW) 1B made of Ga1nAs-1nP and having a thickness of about 50 to 100 angstroms is provided in the center of the crystal layer 15 corresponding to the window for light transmission. At the same time, a crystal layer 17 made of n+Ga1nAs is laminated on the upper surface of the multiple quantum well structure 16.

Passivation (P
anti-reflection film 17a consisting of a
17b and 17c are provided, respectively.

On the antireflection films 17b and 17c, as shown in FIG. 2, an N-side electrode 20 having a ring portion 18 and a protruding portion 19 protruding to the side (left side) of the ring portion 18 is formed. , a part of the N-side electrode 20 is in mutual contact with the upper surface peripheral portion of the crystal layer 17 .

On the crystal layer 15, at a position surrounding the outer periphery of the N-side electrode 20, as shown in FIG. P-side electrode 23 having a protrusion 22 protruding toward
is formed, and a part of the P-side electrode 23 is connected to the crystal layer 1.
It is in mutual contact with the top surface of 5.

An N-side electrode 24 is also formed on the lower surface of the semiconductor substrate 11, as shown in FIG.

Furthermore, in FIG. 1, a control electrode terminal 25 is connected to the N-side electrode 20, an anode terminal 26 is connected to the P-side electrode 23, and a cathode terminal 27 is connected to the N-side electrode 24.

In the photodiode illustrated in FIG. 1, when light with a predetermined energy is irradiated from the direction of the arrow in the figure, the electromotive force described above is generated within the semiconductor stacked structure, so P
When a reverse bias voltage is applied via the side electrode 23 and the N-side electrode 24, a photocurrent flows in the opposite direction.

At this time, independently of the P-side electrode 23 and the N-side electrode 24, the multi-quantum well structure 16 is
An electric field can be applied to the

One of the important characteristics of such a multi-quantum well structure 16 is that the absorption edge wavelength of light can be designed and controlled by its structure and applied voltage.

Therefore, in the above, the N-side electrode 20. P side electrode 2
Applying a voltage to the multiple quantum well structure 18 via 3,
Alternatively, by changing the applied voltage, such as not applying it, the multiple quantum well structure 16 can be used as a filter with different functions.

In FIG. 3, a voltage is applied to the multiple quantum well structure 16 via the N-side electrode 20 and the P-side electrode 23, and the multiple quantum well structure 18 is used as a wavelength-dependent (dispersive) filter for incident light. An example of functioning, that is, the relative relationship between the absorption edge wavelength λC of the light absorption layer 13 and the detected wave input 0 is λ
Enter. In this example, in operation mode C, the photocurrent 1 depends only on the intensity Po (W) of the incident light.
c(P) can now be detected based on the following equation (1).

1c(P)=f(Po) ""(1) In FIG. 4, no voltage is applied to the multiple quantum well structure 1B, and the multiple quantum well structure 16 functions as a filter without wavelength dispersion for incident light. example, that is, light absorption layer 1
The relative relationship between the absorption edge wave input C in 3 and the detected wavelength 7 is an example when λ0 = input C. In this example, in operation mode b, the wavelength change depends on the wavelength change of the incident light. Photocurrent 1b
(P) can now be detected based on the following equation (2).

1b(P)=K(α+, a2)・1e(PI g(input 0
+Δin)−K(αItα2)°f(Pa)°g(λ
G + Δ input) ... - fist ... (2) In the above equation (2), ic (P) is known from the measurement in the operation mode C, and K is the multi-quantum well structure 18
Since it is a constant determined by , g (input 0÷Δinput) can be known based on the change in 1b(P).

Therefore, by determining g (on) in advance, Δon can be detected.

r Effects of the Invention As described above, when using the photodiode according to the present invention, it is possible to detect a change in wavelength, and also a change in the intensity of light.

[Brief explanation of the drawing]

FIG. 1 is a cross-sectional view showing an embodiment of the photodiode according to the present invention, FIG. 2 is a plan view showing the electrode shape of the photodiode according to the present invention, and FIGS. 3 and 4 are according to the present invention. FIG. 5 is a cross-sectional view of a conventional photodiode, and FIG. 6 is a characteristic diagram of the conventional photodiode. 11...Semiconductor substrate 12...Crystal layer 13...Light absorption layer 14...Crystal layer 15...Crystal layer 16... ...Multiple quantum well structure 20...N side electrode 23...P side electrode 24...P side electrode 25...Control electrode terminal 26... ... Anode terminal 27 ... Cathode terminal agent Patent attorney Yoshio Saito

Claims (2)

[Claims] (1) In a photodiode in which a semiconductor laminated structure including a light absorption layer is formed on the laminated surface of a semiconductor substrate, and a P-side electrode and an N-side electrode are provided outside of these semiconductor substrates and the semiconductor laminated structure. . A photodiode, characterized in that a multi-quantum well structure having an absorption edge that mutually coincides with the wavelength of light to be detected is provided on the light incident side of the light absorption layer in the semiconductor laminated structure. (2) The photodiode according to claim 1, wherein the multiple quantum well structure is provided with an electrode for independently applying an electric field thereto.