JPS62132375A - Semiconductor photo detector and manufacture thereof - Google Patents

Abstract

PURPOSE:To obtain a semiconductor photo detector having preferable element characteristics by limiting electron density of N-type InP crystal when introducing Mg as P-type impurity to the N-type InP crystal, thereby simultaneously forming the photo detector and a guard ring. CONSTITUTION:An N-type InP crystal layer 12 having, for example, 2X10<15>cm<-3> of electron density is formed by a liquid-phase growing method on the main surface of an N-type InP substrate crystal 11. Then, a second InP crystal layer 13 is formed by a liquid-phase growing method to bury the etch-removed portion and an X' region to become an inner photo detector. The electron density of the layer 13 is so controlled as to become, for example 6X10<15>cm<-3>. Then, SiO2 and photoresist are selectively formed on the main surface of the InP crystals, and Mg ions are implanted. As a result, the carrier density of the layer 12 is set to 1X10<16>cm-3 or more and 1X10<17>cm<-3> or less of no adverse influence on noise characteristic, a stair type P-N junction photo detector is formed, and the carrier density of the layer 13 is set to 1X10<15>-1X10<16>cm<-3> to form a guard ring.

Description

DETAILED DESCRIPTION OF THE INVENTION [Technical Field of the Invention] The present invention relates to a semiconductor light-receiving element used in an optical transmission system, and more particularly to a semiconductor light-receiving element having the Anorex Lancey effect.

[Prior art and its problems]

The Lancey photodiode (APD), which applies a reverse bias to the p-n junction and multiplies the carriers generated by light, has a high-speed response, internal amplification action,
It has excellent features such as high quantum efficiency.

In particular, APDs using InP materials include InGaAs,
By combining it with InGaAsP, it becomes an excellent light-receiving element for long wavelength bands, and research and development has been actively progressing in recent years.

FIG. 4 is a sectional view showing an example of the structure of an APD, and is intended to explain a conventional example most similar to the present invention. First, the fourth
In the figure, 41 is an n-type InP substrate, and 42 is an n-type avalanche multiplication layer formed on the main surface of the InP substrate. 4
3 is an n-type InP layer. A P-type layer 44 is selectively formed on the main surface of the above n-type layer by Zn diffusion or ion implantation.
This is an APD formed in one step. In the above configuration,
The X region is a light receiving part, and the X region is a part that functions as a guard ring.

An example of the prior art in such a structure is JP-A-56
There are Japanese Patent Laid-open No. 71985 and Japanese Unexamined Patent Publication No. 56-83082. The characteristics of these conventional technologies are that the p-n junction in the X region is formed of, for example, p-type Inp and n-type layer nGaAs;
The p-n junction in the region is formed of p-type InP and n-type InP. In this case, the breakdown voltages of the X region and the X region are different, and the forbidden band width is small. Since the avalanche multiplication layer is made of a material such as InGaAs, which has a relatively small forbidden band width, it has the disadvantage of poor noise characteristics. Also, in the X region, p
The curvature of the -n junction causes electric field concentration, which has the disadvantage that it is not possible to maintain a large breakdown voltage difference with the X region. That is, in the conventional technology, the carrier concentration distribution of the p-n junction is steep in the X and X regions, resulting in a so-called stepped junction type, so it is necessary to stably and reliably obtain the breakdown voltage difference between the light receiving part and the guard ring part. Things were difficult.

Therefore, the basic problem is that good APD characteristics cannot be stably obtained.

In addition, the light receiving part and the guard ring part may be made of different materials or
Although there are many known examples in which they are provided in separate manufacturing processes, their description is omitted because they have little relevance to the present invention.

[Purpose of the invention]

An object of the present invention is to improve the above-mentioned drawbacks and provide a semiconductor light-receiving device having good device characteristics and a method for manufacturing the same.

[Summary of the invention]

This invention utilizes the fact that when Mg is introduced as a p-type impurity into an n-type InP crystal, it exhibits a characteristic hole concentration distribution. It is composed of a semiconductor photodetector that is not found in
Moreover, when obtaining this light-receiving element, the method utilizes Mp ion implantation.

〔Effect of the invention〕

According to the present invention, the following effects can be obtained while maintaining the high speed and high quantum efficiency of APD.

(11 Low noise because an avalanche multiplication layer can be constructed using n-type InP with a relatively large forbidden band width. (2) p
Since the -n junction can be formed by one ion implantation, the structure is excellent in uniformity even though it is a simple back-up process.

(Since two types can be formed: a 31p-n @ junction and a p-1-n type junction (i is a semi-insulating semiconductor), a sufficient breakdown voltage difference between the upper guard ring part of the light receiving part and the guard ring part can be obtained. In other words, the device characteristics The cost of semiconductor light-receiving elements can be reduced by improving and stabilizing the process and simplifying the back-up process.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to FIGS. 1 and 2. FIG. 1 is a cross-sectional view of a light-receiving element, and FIG. 2 shows an example of the hole concentration distribution when Mg is introduced into an InP crystal. First, the light receiving element was constructed as follows. n-type I
The electron concentration on the main surface of the nP substrate crystal 11 is, for example, 2×10
A square n-type IrP crystal layer 12 is formed by liquid phase growth.

Next, using the photoresist as a mask, the InP layer 12 and a portion of the substrate 11 are selectively etched away.

Through this step, an X' region that becomes a circular light receiving section is formed. Next, a second InP crystal layer 13 is immediately formed by liquid phase growth to fill the etched portion and the X' region. The electron concentration of the second InP layer 13 is controlled to be, for example, 6×10 cm. In addition, InP
As another means for forming the layer 13, it is also possible to improve the flatness of the main surface by selectively growing crystals on the portions that have been removed by etching and then growing the crystals further.

Next, Sin and photoresist are selectively formed on the main surfaces of these InP crystals, and Mg ions are implanted. M
The implantation conditions for g are, for example, 15
This was carried out at an accelerating voltage of 9 keV. Next, after removing the Sin and photoresist, phosphoric acid glass is formed on the main surface, and a p-type InP layer 14 and a semi-insulating InPId layer 15 are simultaneously formed by performing heat treatment at, for example, 750° C. for 20 minutes. Next, apply S to the main surface from which the phosphate glass has been removed.
i, N.16 are formed, and electrodes 17 and 18 are formed by vacuum evaporation to complete the light receiving element.

The p-n junction of the light-receiving element constructed as described above had two types of configurations since the p-n junction was formed only once, and had excellent characteristics as a light-receiving element. The reason for this will be explained below with reference to FIG.

In FIG. 2, the hole concentration in the InP crystal can be roughly divided into a steep change region A and a slow change region B. If this region A is used to form a p-n junction in the light receiving part, a stepped p-n junction will be formed, and if region B is used to form a p-n junction in the guard ring part, the carrier concentration will change extremely slowly. graded p-n junction or p-n junction via a semi-insulating layer
It becomes a junction. Therefore, the carrier concentration of the n-type InP layer 12 should be set to lXlocJ or more and to have no adverse effect on the noise characteristics.
10 n or less, forming a stepped p-n junction light receiving part, and setting the carrier concentration of the second InP layer 13 to 1 x 10 ~
The guard ring portion is formed of 1×10 16 crIL'. Although not shown, the p-n junction of the light receiving section and the guard ring section is an EBIC (Electron B
It was confirmed that it was a step-type or semi-insulating p-n junction by evaluating the current (eamInducd Current) characteristics, voltage vs. capacitance change characteristics, and breakdown voltage characteristics.

The breakdown voltage difference of the p-n junction of type 2a constructed in this way was about 40 V, and the light receiving part broke down uniformly first. Furthermore, the Y that becomes the guard ring part
Despite the curvature of the p-n junction in the region, no local breakdown due to electric field concentration occurred, so stable device characteristics were obtained.

[Other Examples]

A second embodiment will be described below with reference to FIG.

In FIG. 3, first, an n-type InP substrate 31 is coated with an n-type InP substrate 31.
P crystal layer 32, n-type InGaAs crystal layer 33, n-type In
A substrate is prepared in which a GaAsP crystal layer 34 and an n-type InP crystal layer 35 are sequentially formed by a liquid phase growth method.

Each crystal layer is grown to have approximately the same lattice constant. This base was made of Si so that a circular light receiving part could be formed.
, Mesa etching is performed using the Na film as a mask. Next, the n-type InP layer 3 is etched to cover the etched portion.
After selectively growing crystals of InP 36, and subsequently removing Si, N, and films, n-type InP 36 is additionally grown on the main surface. In the above configuration, the carrier concentration of n-type InPI 35 is set to 5×10. CrIL is used, and the carrier concentration of the n-type InP layer 36 is 9×10 cm.

Next, as in the first embodiment, Mg ions are selectively implanted into the main surface. The conditions in this case were an acceleration voltage of 200 keV and a dose of 1X10 cm. Next, heat treatment was performed at 700°C for 10 minutes at phosphorus pressure F to form a p-type InPH4
37, and simultaneously form a stepped p-n junction 381 and a p-n junction via a semi-insulating layer 382. Next, the insulating film 39. '411M391, 392 are formed to complete the light receiving element.

In the light receiving element configured as described above, the p-n junction 381 is a step junction with a relatively high concentration, and is a light receiving element that can handle high-speed optical signals, and has a thickness of 1.3 μm.

It can be used as a light receiving element for optical communications that supports light with a wavelength of 1.5 μm.

Figure 2 shows an example of the carrier concentration distribution when Mjl@24 people are added to the InP crystal, but the alf distribution is
Various shapes are shown depending on the conditions of ion implantation and heat treatment. However, using the steep concentration gradient mentioned above,
By setting the carrier concentration of the n-type InP crystal layer, it is possible to configure stepped and inclined p-n junctions.

[Brief explanation of drawings]

FIG. 1 is a sectional view of a light receiving element of the present invention, FIG. 2 is a concentration distribution diagram for explaining the present invention in detail, FIG. 3 is a sectional view of a light receiving element according to another embodiment of the present invention, and FIG. The figure is a sectional view of a conventional light receiving element. 11.31.41・-InP substrate crystal, 12,13,3
2゜33.34, 35, 36, 42.43... n-type crystal layer, 14゜37.44-9 type InP crystal layer, 15,3
82...Semi-insulating layer, 16.39...Insulating film, 17
, 18, 391, 392...electrode.

Claims (3)

[Claims] (1) In a semiconductor light-receiving device formed by introducing one type of P-type impurity into the main surface of an n-type InP crystal to form a p-n junction, the impurity concentration of the first n-type InP layer in contact with the p-type InP layer is 1×10^1^6 to 1×10^1^7 atm/c
m^3, and the impurity concentration of the second n-type InP layer in contact with the p-type InP layer and located around the first n-type InP layer is 1×
10^1^5 to 1x10^1^6 atm/cm^3, and the p-type impurity is Mg. (2) On the main surface of the n-type InP substrate crystal, a first InP crystal layer, an InGaAs crystal layer, an InGaAsP crystal layer, a second
A p-n junction formed by contacting the second InP crystal layer of the base body, which includes an InP crystal layer and a third InP crystal layer sequentially, and the p-type InP layer constitutes a step junction, and the third InP crystal layer and the p-type InP 2. The semiconductor light-receiving device according to claim 1, wherein the p-n junction formed in contact with the two layers is formed through a tilted junction or a crystal layer exhibiting semi-insulating properties. (3) An impurity concentration of 1×10^1^6 to 1×10^1^7 atm provided on an n-type InP substrate crystal via an n-type III and V group mixed crystal layer containing In and P as constituent elements /cm
^-^3 first n-type InP crystal layer, the mixed crystal layer and the first
The impurity concentration provided around the n-type InP crystal layer is 1×10
A step of ion-implanting Mg into the main surface of the substrate that formed the second n-type InP crystal layer of ^1^5 to 1 x 10^1^7 atm/cm^-^3, and a step of ion-implanting Mg at a temperature of 650 °C to 75 °C. 1. A method for manufacturing a semiconductor light-receiving device, comprising the step of forming a pn junction by activating an ion implantation layer.