JPH03211886A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To reduce a dark current flowing to a semiconductor photodetector by burying the bottom of an electrode in a photodetecting layer from the surface of the photodetecting layer. CONSTITUTION:A GaInAs epitaxially grown layer 12 and an AlInAs epitaxially grown layer 13 are sequentially formed on a substrate 11 made of InP, etc., and a photodetecting layer 15 is formed of the layers 12, 13. A pair of Schottky electrodes 16 are formed on the layer 15 formed of the layers 12, 13. The electrodes 16 are isolated from each other in a direction crossing the direction of a light emitted to the layer 15, and buried in the layers 15. Thus, the concentration of an electric field at the edge of the bottom of the electrode 16 can be alleviated, and a dark current of a semiconductor photodetector can be 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 being irradiated with light travel in a direction intersecting the direction of light irradiation, that is, a so-called horizontal light receiving element. Regarding elements.

[Conventional technology]

A conventional example of the semiconductor light receiving element shown in FIG. 3 is shown.

In the conventional semiconductor light-receiving device shown in the figure, an epitaxial growth layer of gallium, indium, arsenic, Ga1nAs, etc. is formed on a substrate 1 of indium-phosphide, InP, etc., as a light-receiving layer 2. It has a structure in which a pair of electrodes 3 are formed.

[Problem to be solved by the invention]

In the semiconductor light-receiving device having such a structure, when a voltage is applied between the electrodes 3, as shown in the figure, the electric field is concentrated at the edge of the bottom surface of the electrode facing the light-receiving layer 2, and this is the main cause of darkening. A current is generated.

Therefore, in view of the above-mentioned circumstances, an object of the present invention is to reduce the dark current flowing through the semiconductor light receiving element.

[Failure to solve the problem]

In order to achieve the above object, the semiconductor light-receiving element according to the present invention is configured such that at least the bottom surface of the electrode formed in the light-receiving layer is buried in the light-receiving layer from the surface of the light-receiving layer.

[Effect]

With such a configuration, electric field concentration on the edge portion of the bottom surface of the electrode is alleviated.

〔Example〕

Embodiments of the present invention will be described below 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, an epitaxial growth layer of gallium, indium, arsenic, Ga1nAs is formed on a substrate 11 of indium-phosphide InP, etc.
An epitaxially grown layer 13 of , aluminum indium H$A, and 171 nAs is formed in this order, and these two epitaxially grown layers 12 and 13 constitute a light-receiving layer 15. Note that the thicknesses of the two epitaxially grown layers 12 and 13 are 1 μm and 0.2 μm, respectively. A pair of Schottky electrodes 16 (T i / P L / A
u) is formed. This pair of electrodes 16 are spaced apart from each other in a direction intersecting the direction of light irradiated onto the light-receiving layer 15, and both are embedded in the light-receiving layer 15. Note that in order to form the electrode 16 by embedding it in the light-receiving layer 15, before forming the electrode by vapor deposition,
Four portions in which electrodes are embedded are formed on the surface of the light-receiving layer 15 by etching or the like, and the electrodes may be formed in these portions. By embedding the electrode 16 in the light-receiving layer 15 in this manner, as shown in the figure, the concentration of electric field on the edge portion of the bottom surface of the electrode can be alleviated, and dark current can be 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, when a voltage is applied between the electrodes in a semiconductor photodetector with a conventional structure, the electric field concentrates significantly on the edge of the bottom of the electrodes, and breaks down when the applied voltage exceeds 1.5V. It ends up. For this reason, although the dark current is 10 nA or less when the applied voltage is IV or less, when the applied voltage becomes 3V, the dark current suddenly increases to 1 μA. In contrast, in the semiconductor light-receiving element shown as an example of the present invention, even when the applied voltage is about 4 V, the dark current flows only about 25 nA, which shows that the dark current is significantly reduced.

The table below shows the comparison results of dark current when the applied voltage is 4V.

Incidentally, in the embodiment shown in FIG. 1, the electrode 16 is entirely buried in the light-receiving layer 15 and does not protrude from the surface of the light-receiving layer 15, but in the present invention, the electrode 16 is At least the bottom surface of the electrode may be buried in the light-receiving layer, or a portion of the electrode may protrude to the outside from the surface of the light-receiving layer.

Furthermore, in the embodiment of the semiconductor light-receiving device according to the present invention shown in FIG. 1, the light-receiving layer has a structure composed of two epitaxially grown layers, but the light-receiving layer may also be composed of a single layer. . Further, it is preferable to round the edge portion of the bottom surface of the electrode, as this can further alleviate the electric field concentration on that portion.

〔Effect of the invention〕

As described above, according to the present invention, concentration of electric field on the edge portion of the bottom surface of the electrode can be alleviated, and dark current of the semiconductor light-receiving element can be reduced.

[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, 12.13... Epitaxial growth layer, 15... Light receiving layer, 16... Electrode. Comparison of 1 shaku of Shitenchogu J Diagram Box, Part 2

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, wherein at least the bottom surface of the electrode is buried in the light-receiving layer from the surface of the light-receiving layer.