JPH03211887A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To reduce a dark current flowing to a semiconductor photodetector by bonding a reverse conductivity type semiconductor layer to a photodetecting layer to the opposite side surface of the photodetecting layer to a photodetecting surface. CONSTITUTION:A P-type semiconductor layer 12 is formed on a substrate 11 made of InP, etc., and an n-type GaInAs epitaxially grown layer is formed as a photodetecting layer 13 on the layer 12. Since the layer 13 is not Schottky- connected, an AlInAs epitaxially grown layer 15 is further formed thereon, and a pair of Schottky electrodes 16 are formed on the upper surface. Thus, since a structure in which the reverse conductivity type layer 12 to the layer 13 is bonded to the opposite side surface of the layer 13 to the photodetecting surface to which a light is emitted is formed, carrier existing in the layer 13 is depleted, and the resistance of the layer 13 is increased. Thus, a current scarcely flows to the layer 13, and a dark current is reduced.

Description

[Detailed Description of the Invention] [Industrial Application Field] The present invention relates to a semiconductor light receiving element in which carriers generated by light irradiation travel in a direction intersecting the light irradiation direction, that is, a so-called horizontal light receiving element. Regarding elements.

[Conventional technology]

Semiconductor photodetector (Metal-8emi) shown in FIG.
A conventional example of a conductor-Metal M SM light receiving element) is shown below. The conventional semiconductor photodetector shown in the figure is
It has a Schottky electrode on its surface, and a light-receiving layer 2 is an epitaxially grown layer of gallium, indium, arsenic, Ga InAs, etc. on a substrate 1 of indium-phosphorus InP, etc.
Furthermore, an epitaxial growth layer 3 of aluminum, indium, arsenic, ANInAs, etc. is formed on this light-receiving layer 2. A pair of Schottky electrodes 5 of Ti/Pt/Au are formed on the epitaxial growth layer 3. The pair of electrodes 5 are spaced apart from each other in a direction intersecting the direction of light irradiated onto the light-receiving layer 2 . Incidentally, the epitaxially grown layer 3 is formed because a Schottky connection cannot be made with the light-receiving layer 2 of Ga1nAs.

In the semiconductor light-receiving element having such a structure, the dark current of the light-receiving element was reduced by the Schottky electrode 5 formed on the surface.

(Problem to be Solved by the Invention) However, in the conventional semiconductor photodetector described above, when the voltage applied between the electrodes is in the range of -11 to +IV, the dark current is less than 10 nA due to Schottky characteristics. However, if the voltage applied between the electrodes exceeds 1.5V, the Schottky characteristic will break down.
When a voltage of about 5V is applied, a dark current of about 2 μA will flow. The aim is to reduce the

[Means to solve the problem]

In order to achieve the above object, the semiconductor light-receiving device according to the present invention has a structure in which a semiconductor layer of a conductivity type opposite to that of the light-receiving layer is bonded to the surface of the light-receiving layer opposite to the light-receiving surface.

[Effect]

With such a configuration, carriers existing in the light-receiving layer are depleted, and the resistance of the light-receiving layer increases.

[Example] Hereinafter, an example of the present invention will be described with reference to FIG.

FIG. 1 shows a cross section of an embodiment of a semiconductor light receiving element according to the present invention. In the illustrated embodiment of the present invention, a semiconductor layer 12 of p-1nP or p-GaInAs is formed on a substrate 11 of indium-phosphide InP, etc., and a semiconductor layer 12 of p-1nP or p-GaInAs is formed on this semiconductor layer 12. An epitaxially grown layer is formed as the light-receiving layer 13. This light-receiving layer 13 is not doped, but is n-type. Ga1nAs light-receiving layer 13
Since it is not possible to make a Schottky connection, in order to obtain a Schottky connection, aluminum, indium
An epitaxial growth layer 15 of arsenic Aj71nAs is formed. On the upper surface of the epitaxial growth layer 15, a pair of shield electrodes 16 (T i /
Pt/Au) is formed. The pair of electrodes 16 are spaced apart from each other by M in a direction intersecting the direction of light irradiated onto the light-receiving layer 13 .

In this way, the light-receiving layer 13 and the semi-conductive semiconductor layer 1 are formed on the surface of the light-receiving layer 13 opposite to the light-receiving surface that is irradiated with light.
2 are joined, carriers existing in the light receiving layer 13 are depleted, and the resistance of the light receiving layer 13 increases. Therefore, it becomes difficult for current to flow through the light-receiving layer 13, and dark current is reduced.

FIG. 2 shows a comparison of dark current measurement results between the semiconductor light receiving element described above as an example of the present invention and a conventional semiconductor light receiving element. Note that the electrode spacing of the compared semiconductor light receiving elements was 5 μm in all cases. In the figure, the dashed line indicates the dark current of the semiconductor light receiving element described above as an example of the present invention, and the solid line indicates the dark current of the conventional semiconductor light receiving element. As is clear from the figure, in the semiconductor light-receiving element of the conventional structure, when the voltage applied between the electrodes becomes 1.5 V or more, breakdown occurs and the dark current increases rapidly. For this reason, when the applied voltage is below IV, the dark current is below IonA, but when the applied voltage becomes 5 .mu.A, the dark current suddenly increases to 2 .mu.A. On the other hand, in the semiconductor photodetector shown as an example of the present invention, the breakdown voltage is the same as that of the conventional one, but the rapid increase in dark current after breakdown is suppressed, and even when the applied voltage is about 5V, It can be seen that the dark current flows only about 100n8, and the dark current is significantly reduced. Note that when the applied voltage is 5 V, the dark current in the semiconductor light receiving element is reduced to about 1/20 compared to the conventional one.

〔Effect of the invention〕

As described above, according to the present invention, by depleting the light-receiving layer, the resistance of the light-receiving layer can be increased, thereby reducing the dark current of the semiconductor light-receiving element.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view showing an embodiment of a semiconductor photodetector according to the present invention, and FIG. 2 is a comparison of dark current between the semiconductor photodetector having the structure shown in FIG. 1 and the conventional semiconductor photodetector. FIG. 3 is a sectional view showing a conventional semiconductor light receiving element. DESCRIPTION OF SYMBOLS 11... Substrate, 12... Semiconductor layer, 13... Light receiving layer, 16... Electrode.

Claims (1)

[Claims] A semiconductor light-receiving element comprising a light-receiving layer that generates carriers when irradiated with light, and at least a pair of electrodes provided on the light-receiving layer at a distance from each other in a direction intersecting the direction in which light is irradiated. . A semiconductor light-receiving element, characterized in that a semiconductor layer having a conductivity type opposite to that of the light-receiving layer is bonded to a surface of the light-receiving layer opposite to the light-receiving surface.