JPH0556669B2 - - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION (a) Field of Application This invention relates to a near-infrared light receiving element that exhibits high sensitivity to light in the near-infrared region.

(b) Prior art and problems to be solved by this invention Thin-film semiconductor light-receiving elements such as PbS (lead sulfide) and CdS (cadmium sulfide) are commercially available as light-receiving elements that detect light using the photoconductive effect. In addition, light receiving elements using single crystals are also known.

However, the light receiving element has photosensitivity over the visible light region and the infrared light region. Therefore, when these light-receiving elements are used as infrared light-receiving elements in an environment of natural light or indoor light, visible light, which is disturbance light, is received as noise. For this reason,
When the light receiving element receives infrared light emitted from a commercially available GaAs (gallium arsenide) infrared light emitting diode, a filter for blocking indoor light is required. If this filter is provided in the light-receiving element, the dielectric constant of the propagating medium becomes discontinuous, resulting in a weakening of the intensity of the infrared rays, making signal processing such as providing an amplifier in the light-receiving circuit complicated and expensive.

Furthermore, the problem of receiving visible light as disturbance light is
It also existed in photodiodes with Pn junction or pin junction structures.

An object of the present invention is to provide an inexpensive near-infrared receiving element that exhibits high sensitivity only in a specific region of near-infrared rays.

(c) Means for solving the problem In order to solve the above-mentioned problem, the present invention uses a semi-insulating GaAs single crystal, and the angle is perpendicular or acute to the light-receiving surface, and the angle is smaller than the area of the light-receiving surface. It also forms a large electrode surface. Furthermore, the light-receiving surface is made into a lap surface, or a non-electrode surface having a width of at least 1 micrometer or more from the ridgeline of the light-receiving surface is formed on a surface of the electrode surface adjacent to the light-receiving surface.

(d) Effect A high-purity GaAs single crystal that exhibits semi-insulating properties at room temperature has an energy level in the central part of the forbidden band, and its absorption coefficient is generally 1/several centimeters, approximately
It has an extrinsic light absorption phenomenon due to free electron excitation in the near-infrared light energy range from 0.7eV to approximately 1.4eV. By utilizing the properties of this GaAs single crystal and increasing the electrode area compared to the light receiving area to obtain a high photocurrent, near-infrared rays can be received with high sensitivity.

(E) Embodiment FIG. 1 shows a first embodiment of this invention.
indicates a semi-insulating GaAs single crystal 1. this
GaAs single crystal 1 is formed into a rectangular parallelepiped, one surface of which serves as a light-receiving surface 1a. This light receiving surface 1a is polished to a mirror surface. Two parallel surfaces perpendicular to the length direction of the light-receiving surface 1a form electrode surfaces, and the electrodes 2 are provided on these electrode surfaces by ohmic contact. The area of this electrode 2 is larger than the area of the light receiving surface 1a.

FIG. 2 shows a spectral characteristic diagram when light is irradiated onto the light receiving surface 1a of the near-infrared light receiving element configured as shown in FIG. Figure 2 shows that when moving from low optical energy (long wavelength) to high optical energy (short wavelength), the photocurrent increases continuously from approximately 0.7 eV to approximately 1.4 eV, and after approximately 1.4 eV. This shows that the photocurrent suddenly decreases. Therefore, it can be seen that the light-receiving element exhibits low sensitivity to visible light (1.6 eV or more) and high sensitivity to near-infrared rays. For example, commercially available GaAs infrared light emitting diodes have a maximum emission intensity of about 1.3 eV, and therefore exhibit high sensitivity to that light.

Further, the area of the electrode 2 of the light receiving element is the light receiving surface 1
Since it is large compared to the area of a, a large photocurrent can be extracted even when a low voltage is applied to the electrode 2.

Figure 3 shows the light-receiving surface 1a of the GaAs single crystal 1 in Figure 1.
FIG. 4 is a diagram showing changes in spectral characteristics when polished to a lap surface instead of a mirror surface. As shown in Figure 3, in the infrared region, there is no difference in photocurrent sensitivity to incident light between the lap surface and the mirror surface, whereas in the visible light region, the incidence on the lap surface is higher than that on the mirror surface. photocurrent sensitivity is significantly reduced. Therefore, by polishing the light-receiving surface 1a of the GaAs single crystal 1 into a lap surface, the effect of shielding visible light becomes more pronounced.

FIG. 4 shows a second embodiment of the invention.
In this embodiment, two parallel planes perpendicular to the length direction of the light-receiving surface 3a of the GaAs single crystal 3 having the same shape as the GaAs single crystal 1 shown in FIG. A non-electrode surface 4 is provided on which no electrode is provided by a width of at least approximately 1 micrometer from one longitudinal ridgeline, and the remaining surface serves as an electrode surface on which an electrode 5 is formed by ohmic contact. There is. The area of each electrode 5 is larger than the area of the light receiving surface 3a, and is polished to a mirror surface.

High-purity GaAs single crystals (commercially available) that exhibit semi-insulating properties at room temperature belong to direct transition semiconductors, and reflect incident light with optical energy greater than the forbidden band width at the light-receiving surface, or It has the property of absorbing within a micrometer. Also,
GaAs single crystal has a forbidden band width of 1.4 eV at room temperature, which is in the near-infrared light energy range. Therefore, even if the GaAs single crystal is irradiated with visible light having a light energy of about 1.4 eV or more, the light will not reach a distance of 1 micrometer or more from the light receiving surface.

FIG. 5 shows a spectral characteristic diagram when light is irradiated onto the light receiving surface 3a of the near-infrared light receiving element configured as shown in FIG. As shown in FIG. 5, the light-receiving element of FIG. 4 exhibits significantly lower sensitivity to light energy in the visible light range than the light-receiving element of FIG. 1. Therefore, a simple structure in which the non-electrode surface 4 is provided on the GaAs single crystal 3 can reliably block light in a high energy range of 1.4 eV or more.

FIG. 6 shows a third embodiment of the invention.
In the case of this embodiment, one electrode surface is formed at an acute angle inclined by several degrees with respect to the light-receiving surface 6a of the semi-insulating GaAs single crystal 6, and the electrode 7 is provided on this electrode surface by ohmic contact. There is. Furthermore, an electrode 8 is also provided on an electrode surface that is perpendicular to the light-receiving surface 6a that faces the electrode 7. The area of each of the electrodes 7 and 8 is larger than the area of the light-receiving surface 6a, and is provided larger in the direction in which light travels.

By tilting the electrode surface 7 with respect to the light-receiving surface 6a, a photocurrent accompanying incident light is generated across the entire electrode surface, and the light irradiation effect decreases as the electrode surface moves away from the light-receiving surface 6a. This phenomenon can be removed and it becomes possible to perform better photocurrent detection.

FIG. 7 shows an example of a specific circuit configuration diagram using the above-mentioned near-infrared light receiving element. For example, the light-receiving surface 3a of the GaAs single crystal 3 constructed as shown in FIG. 4 is arranged so that the infrared rays from the infrared light emitting diode 9 are perpendicularly incident thereon. A positive terminal of a power source 10 is connected to one electrode 4 of this GaAs single crystal 3, and the other electrode is grounded via a resistor. Further, two side surfaces of the GaAs single crystal 3 are coated with a light shielding film 11, so that incident light is restricted only to the light receiving surface 3a. With this configuration, the GaAs single crystal itself can sense near-infrared light to obtain a photocurrent output.

(E) Effect This invention provides a near-infrared light receiving element that is obtained by combining the characteristics and shape of the element itself so as to have high sensitivity in the near-infrared region and low sensitivity to visible light. , there is no need for a filter to block visible light, which was required in the past. Furthermore, since no filter is used, it is possible to prevent the photodetection signal from weakening, and there is no need to provide an auxiliary circuit such as a noise filter for processing the photodetection signal, making it inexpensive and easy to process the signal.

Furthermore, since the light-receiving surface of the present invention is formed as a lap surface, the sensitivity to visible light is significantly reduced, and visible light can be reliably blocked. Further, according to another aspect of the present invention, since the non-electrode surface is formed with a width of at least 1 micrometer from the ridgeline of the light receiving surface, visible light cannot reach the electrode surface and the sensitivity to visible light is significantly reduced. It can detect near-infrared rays with high sensitivity.

[Brief explanation of the drawing]

Fig. 1 is a perspective view showing an embodiment of the present invention;
The figure is a spectral characteristic diagram of the device shown in FIG. 1, FIG. 3 is a spectral characteristic diagram showing a comparison when the light-receiving surface of the device shown in FIG. FIG. 5 is a spectral characteristic diagram of the device shown in FIG. 4, FIG. 6 is a perspective view showing a third embodiment of the present invention, and FIG. 7 is a near-infrared light-receiving device of the present invention. FIG. 3 is a diagram showing an example of a specific circuit configuration used. 1, 3, 6...GaAs single crystal, 1a, 3a, 6
a... Light receiving surface, 2, 5, 7, 8... Electrode, 4...
Non-electrode surface, 9... Infrared light emitting diode, 10...
...power supply, 11...light-shielding film.

Claims (1)

[Claims] 1. In order to detect near-infrared rays with high sensitivity, an electrode surface is formed at a right angle or an acute angle to the light-receiving surface of a semi-insulating GaAs single crystal and has a larger area than the light-receiving surface. . A near-infrared light-receiving element, characterized in that the light-receiving surface is a wrap surface. 2. In order to detect near-infrared rays with high sensitivity, an electrode surface is formed at a right angle or an acute angle to the light-receiving surface of the semi-insulating GaAs single crystal and has a larger area than the light-receiving surface. A near-infrared light-receiving element, characterized in that a non-electrode surface having a width of at least 1 micrometer or more from the ridgeline of the light-receiving surface is formed on a surface adjacent to the light-receiving surface.