JPH05206496A - Semiconductor light receiving device - Google Patents

Abstract

PURPOSE:To prevent a drop in reaction speed or inhibit deterioration in the sensibility of a semiconductor light receiving device by installing a semiconductor layer having a larger band gap energy than that of an optical absorption layer and a carrier concentration similar or below that of the optical absorption layer. CONSTITUTION:A semiconductor light receiving device 30 consists of an follows: An n-Ga0.29In0.62P0.38 layer 31 having the carrier concentration of 5X10<15>/cm<3> and the thickness of 0.5 microns, an n-GaInAs layer 12 having the carrier concentration of 1X10<15>/cm<3> and the thickness of 3 microns and an n-InP layer 13 having the carrier concentration of 1X10<16>/cm<3> and the thickness of 1 micron are laminated one after another on an n<+>-InP substrate 11. There are also formed a 2 micron thick p<+>-GaInAs layer 25 and a 1 micron thick p<+>-InP layer 21 respectively. What is more, there is formed a p-n junction 14 on the boarder between each of the layers 12 and 20. An n-type electrode 15, a p-type electrode 16, a dielectric surface protection film 17 and a dielectric reflection preventative film are laid out therein respectively.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor light receiving element having a wide dynamic range in sensitivity.

[0002]

2. Description of the Related Art FIG. 3 is a schematic view showing a sectional structure of a conventional light receiving element of this type. In the light receiving element 10 having the conventional structure, n
^{On the − −} InP substrate 11, GaInAs having a low carrier concentration is formed.
The layer 12 and the n-InP layer 13 that is a cap layer are stacked. The p ⁺ -GaInAs layer 20 and the p ⁺ -InP layer 21 are formed by selectively introducing p-type impurities into the layers 12 and 13.
The pn junction 14 is formed by forming the. Further, the n electrode 15 and the dielectric insulating film 17 are formed on the n-type InP layer 13, and the p electrode 16 is formed on the p-type InP layer 21.
^A dielectric antireflection film 18 is formed on each ⁺ -InP substrate 11. In the present light receiving element 10, the signal light 19 is incident from the substrate 11 side. As described above, the light receiving element 10 is a back-illuminated pin photodiode that uses the GaInAs layer 12 as a light absorption layer. Next, the operation of the light receiving element will be described. This light receiving element is used by applying a reverse bias voltage between the electrodes 15 and 16. At this time, the electric field distribution formed inside the light receiving element along the line AA ′ shown in FIG. 3 will be described. First, the distribution in the so-called dark state where no optical signal is incident is shown at 41 in FIG.
The distribution 41 when the optical signal 19 is not incident changes when the optical signal is incident. That is, the electric field intensity distribution upon incidence of an optical signal depends on the signal intensity of the incident light.

[0003]

As described above, the optical signal 19 is incident from the substrate 11 side, and its wavelength is 1.
Since it is 5 microns, it is absorbed only inside the GaInAs layers 12 and 20. The distribution 42 of photoexcited carriers formed by this light absorption exponentially changes in the traveling direction of light. Of the photoexcited carriers, holes are layer 2
In the direction of 0, the electrons travel in the direction of the layer 11, respectively. As a result, the hole density inside the layer 12 near the layer 20 becomes high, while the electron density inside the layer 12 near the layer 11 becomes high. The distribution of photoexcited carriers generated inside the layer 12 during traveling changes the electric field distribution inside the layer 12. When the signal intensity of the incident light is small, the change amount of the electric field distribution is negligible, but the change amount cannot be ignored as the signal intensity of the incident light increases. Since the distribution of photoexcited carriers during traveling is in the direction of decreasing the electric field intensity inside the light absorption layer 12, the electric field intensity distribution changes from 41 to 43 above a certain incident light intensity. Electric field strength distribution 43
Then, since the electric field intensity distribution becomes almost zero in the vicinity of the layer 11 inside the layer 12, the depletion layer that has spread in the dark state disappears. As a result, the photoexcited carriers generated in the non-electric field region in the light absorption layer 12 do not travel due to the electric field, so that the response speed of the light receiving element becomes extremely slow.
Further, some of these carriers disappear due to recombination and the like, which causes deterioration of sensitivity. As described above, the light receiving element having the conventional structure has problems such as a slow response speed to a strong optical signal and deterioration of sensitivity.

An object of the present invention is to provide a semiconductor light receiving element in which the response speed does not decrease even with a strong optical signal and the sensitivity does not deteriorate.

[0005]

In order to achieve this object, the semiconductor light receiving element according to the present invention provides a bandgap energy larger than that of the light absorbing layer between the light absorbing layer and the n ⁺ semiconductor layer of the light receiving element. And a semiconductor layer having a carrier concentration equal to or lower than that of the light absorption layer.

[0006]

With such a structure, in the semiconductor light receiving element according to the present invention, the disappearance of the depletion layer that occurs when a strong optical signal as described above is incident can be limited to the inside of the newly provided semiconductor layer. it can. In this way, since no electric field region is formed inside the light absorption layer, carrier travel is not hindered and the response speed and sensitivity are not deteriorated.

[0007]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS FIG. 1 is a sectional structural view of the first embodiment according to the present invention. The structure of the semiconductor light receiving element 30 of the present invention is as follows. On the n ⁺ -InP substrate 11, an n-type having a carrier concentration of 5 × 10 ¹⁵ / cm ³ and a thickness of 0.5 μm
Ga _0.29 In _0.71 As _0.62 P _0.38 layer 31 and n-Ga having a carrier concentration of 1 × 10 ¹⁵ / cm ³ and a thickness of 3 μm
InAs layer 12 and carrier concentration 1 × 10 ¹⁶ / cm ³
And an n-InP layer 13 having a thickness of 1 micron is stacked, and a p ⁺ -GaInAs layer 20 having a thickness of 0.2 micron and a thickness of 1 are formed by p-type impurities selectively introduced.
A micron p ⁺ -InP layer 21 is formed and a pn junction 14 is formed at the boundary between the layers 12 and 20. Also,
n-type electrode 15, p-type electrode 16, dielectric surface protective film 17,
A dielectric antireflection film 18 is provided.

Next, the operation of the light receiving element 30 will be described. A voltage of 5 V is applied to the electrode 15 with a positive polarity and to the electrode 16 with a negative polarity. The electric field intensity distribution formed inside the light receiving element 30 during operation will be described. What is denoted by 44 in FIG. 2 is an electric field intensity distribution formed in the BB ′ cross section in FIG. 1 when no optical signal is incident. Since the optical signal is light having a wavelength of 1.5 μm, the InP layer 11 and Ga _0.29 In _0.71
It is not absorbed by the As _0.62 P _0.38 layer 31. Therefore, the carriers excited by the incident light signal are generated only inside the layer 12 and have an exponential distribution as indicated by 45 in FIG. Of the photoexcited carriers, holes travel in the direction of the layer 20 and electrons travel in the direction of the layer 11. With the traveling of the photoexcited carriers, the electric field intensity distribution inside the layer 12 changes from the value in the dark state indicated by 44. Since the magnitude of this change depends on the amount of incident light, it is generally difficult to show, but an example is shown by 46 in the figure. In the electric field intensity distribution indicated by 46, it can be seen that the region where the electric field intensity is zero is limited to the inside of the layer 31. Therefore, the disappearance of the depletion layer occurs only inside the layer 31, and the layer 12 that is the light absorption layer
It does not occur internally. Therefore, photoexcited carriers are always generated in the electric field application region.

Further, by adjusting the thickness of the layer 31, the above-mentioned effect can be obtained for an optical signal of any intensity. In the above embodiment, the substrate is n ⁺ -In
Although P is used, a semi-insulating substrate may be used.
Further, in the above-described embodiment, the light has a back-illuminated structure from the substrate side, but the present invention is also effective as a structure in which light is incident from the front surface on the side opposite to the substrate.

In the first embodiment, the structure in which Ga _0.29 In _0.71 As _0.62 P _0.38 is used for the semiconductor layer 31 has been described, but as described above, if the layer 31 is transparent to the incident light signal. good. That is, for example, n-type Ga _x In _1-x As _y P _1-y (0 ≦ x <0.46 with a carrier concentration of 5 × 10 ¹⁶ / cm ³ or less and lattice-matched to InP).
A 7,0 ≦ y <1) layer can be used as the layer 31. Layer 3 if the incident light signal is 1.55 micron wavelength light
1 is G having a composition of y ≦ 0.8 and x ≦ 0.374.
An a _x In _1-x As _y P _1-y layer can be used. It is known that the values of x and y that determine the composition have a relationship of x = 0.467y depending on the condition of lattice junction with the InP semiconductor.

[0011]

As described above, in the semiconductor light receiving element of the present invention, it is possible to prevent the generation of photoexcited carriers in the non-electric field region which occurs in the light receiving element of the conventional structure, so that the response speed and the sensitivity are not deteriorated. Significantly improved.

[Brief description of drawings]

FIG. 1 is a sectional view showing a sectional structure view of a first embodiment of the present invention.

FIG. 2 is a characteristic diagram showing an electric field intensity distribution and a photoexcited carrier distribution in a BB ′ cross section of FIG.

FIG. 3 is a cross-sectional structure diagram of a semiconductor light receiving element having a conventional structure.

FIG. 4 is a characteristic diagram showing an electric field intensity distribution and a photoexcited carrier distribution in the AA ′ cross section of FIG. 3.

[Explanation of symbols]

Reference Signs List 10 semiconductor light receiving element of conventional structure 11 n-type InP substrate 12 GaInAs light absorption layer 13 n-type InP layer 14 pn junction 15 n-type electrode 16 p-type electrode 17 dielectric protective film 18 dielectric antireflection film 19 incident optical signal 20 p ⁺ −GaInAs layer 21 p ⁺ −InP layer 30 Semiconductor light receiving element of the present invention 31 n ⁻ −Ga _0.29 In _0.71 As _0.62 P _0.38 layer 41 Electric field intensity distribution in dark state in conventional light receiving element 42 Excited by incident light signal Carrier distribution 43 Electric field intensity distribution when light is incident on a conventional light receiving element 44 Electric field intensity distribution in a dark state on the light receiving element of the present invention 45 Carrier distribution excited by an incident light signal 46 Light by the light receiving element of the present invention Electric field strength distribution at incidence

 ─────────────────────────────────────────────────── ─── Continuation of the front page (72) Inventor Junichi Yoshida 1-1-6 Uchisaiwaicho, Chiyoda-ku, Tokyo Nihon Telegraph and Telephone Corporation

Claims (2)

[Claims] 1. A pin photodiode having a pin structure, which has a bandgap energy larger than that of a semiconductor layer forming a light absorption layer of the pin photodiode and has an n-type of 5 × 10 ¹⁶ / cm ³ or less. A semiconductor light-receiving element, wherein a semiconductor layer having a carrier concentration is in contact with the semiconductor light absorption layer and is arranged on the n-type semiconductor layer side. 2. A GaInA substrate formed on an InP substrate.
In a pin photodiode using the s layer as an absorption layer,
N-type Ga _x In _1-x As _y P _1-y (0 ≦ x with carrier concentration of 5 × 10 ¹⁶ / cm ³ or less and lattice-matched to InP
<0.467, 0 ≦ y <1) layer is in contact with the GaInAs layer and is arranged on the n-type semiconductor layer side.