JPH0677517A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To obtain a semiconductor photodetector capable of selectively obtaining an output current for a specified polarization light, by a method wherein periodic structure has a period almost generating quantum effect in the face direction. CONSTITUTION:On the InP substrate 1, the following are formed; a polarization light layer 7 composed of GaAs/InAs quantum thin line periodic structure, an InP layer 2 to which N-type impurities are added, an InGaAs layer 3 to which no impurities are added, an InGaAs layer 4 to which P-type impurities are added, and an AuZn metal electrode 5. After mesa etching is progressed as far as the N-type InP layer 2, an AuGeNi metal electrode 6 is formed on the N-type InP layer 2. A polarization light selection layer 7 is constituted of quantum wire periodic structure composed of GaAs semiconductor thin lines 8 and Inks semiconductor wires 9. Hence, in the polarization light selection layer 7, the transmittance of the polarization light parallel with the quantum thin lines is smaller than that of the polarization light vertical to the quantum wires so that an input light signal having polarization light vertical to the quantum wires can be selectively received.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor photodetector having a polarization selection function.

[0002]

2. Description of the Related Art A semiconductor photodetector is conventionally formed by diffusing impurities or implanting impurities in a crystal substrate, or by laminating semiconductor layers parallel to the surface of the substrate by a crystal growth technique. However, the progress of crystal growth technology has made it possible to form a periodic thin line structure having a period of a quantum effect in the in-plane direction of the substrate or less.

FIG. 4 shows a structural example of a conventional semiconductor photodetector. On the InP substrate 1, an n-type impurity-doped InP layer 2, an undoped impurity-doped InGaAs layer 3, a p-type impurity-doped InGaAs layer 4, and an AuZn metal electrode 5 are formed. After forming all layers and performing mesa etching to the n-type InP layer 2, the AuGeNi metal electrode 6 is formed on the n-type InP layer 2.

The semiconductor photodetector having the above structure has a pin
An optical signal is applied to the pin junction while applying a reverse bias voltage to the junction. photons are absorbed in the i-layer,
Electron-hole pairs are generated. The generated electron-hole pairs are pi
An electric field applied to the n-junction causes it to flow toward the electrodes,
It is taken out from the electrode as a photocurrent.

Since the conventional semiconductor photodetector does not have a selection function for specific polarized light, its light receiving sensitivity does not depend on the polarization direction of input light.

[0006]

Since the conventional semiconductor photodetector cannot select the polarized light, it requires an optical element such as an analyzer to selectively detect the specific polarized light, and the optical device Had the drawback of being complicated.

An object of the present invention is to provide a semiconductor photodetector which can selectively obtain an output current for a specific polarized light.

[0008]

A first semiconductor photodetector according to the present invention is a semiconductor photodetector having a pn junction composed of a p-type semiconductor and an n-type semiconductor formed on a semiconductor substrate. A semiconductor thin line having a first forbidden band width and a semiconductor thin line having a second forbidden band width wider than the semiconductor thin line having the first forbidden band width on the light incident surface side of the junction; It is characterized in that the periodic structure has a period that causes a quantum effect in the in-plane direction.

A second semiconductor photodetector according to the present invention has a pin junction formed by forming an i-type semiconductor between the p-type semiconductor and the n-type semiconductor in the first semiconductor photodetector. It is characterized by having.

[0010]

The principle of the present invention will be described with reference to the drawings. In the semiconductor photodetector with the conventional configuration shown in FIG. 4, a reverse bias voltage is applied to the pin junction and a photocurrent can be obtained by irradiating the i layer with an optical signal. FIG. 2 and FIG. 3 are diagrams for explaining the light receiving characteristics regarding the polarization of the semiconductor photodetector of the present invention. FIG. 2 is a structural view of a quantum wire forming the polarization selection layer, and FIG. 3 is a view of reflectance anisotropy of the quantum wire.

In the present invention, as shown in FIG. 2, the polarization selection layer 7 has a quantum thin wire structure in which a GaAs semiconductor thin wire 8 and an InAs semiconductor thin wire 9 are arranged at a period such that a quantum effect occurs. The quantum wire structure can be realized by a metal organic chemical vapor deposition method, a metal organic chemical vapor deposition method, or a molecular beam epitaxial growth method. For details of the quantum wire structure manufacturing method, see, for example, the magazine Applied Physics Letters (Applied).
Physics Letters), Volume 50, 198
7 years, pp. 824-826, "(AlAs) _0.5 (GaAs) _0.5 fractional superlattice ((AlA) grown on (001) vicinal surface by metalorganic chemical vapor deposition.
s) _0.5 (GaAs) _0.5 fractional-lay
er superlattices grown on
(001) vicinal surface by
metal organic chemical v
Apor deposition) ". When the period of the semiconductor wire becomes small enough to cause quantum effect, the band edges are observed separately depending on the incident polarization direction. Then, as shown in FIG. 3, optical anisotropy occurs in which the reflectance and the transmittance differ depending on the polarization direction. More specifically, on a GaAs substrate whose plane orientation is the (001) plane, GaAs parallel to the [110] direction
In the quantum wire structure formed from the wires and the InAs wires,
InAs has a narrower band gap than GaAs,
Carriers are confined in the [-110] direction. Due to this carrier confinement effect, transitions involved in heavy holes and transitions involved in light holes are separated. This is because, in FIG. 2, when the electric field of the incident light is polarized light a parallel to [110], the transition involved in the heavy holes on the long wavelength side is allowed, and in the case of the vertically polarized light b, the transition is prohibited. . Therefore, the quantum wire structure can be used for the polarization selection layer of the semiconductor photodetector. The wavelength λ _D having a large reflectance difference RD shown in FIG. 3 is matched with the incident light wavelength λ _in . In the semiconductor photodetector designed in this way, the transmittance for the polarized light a whose polarization direction is parallel to [110] is smaller than the transmittance for the polarized light b perpendicular to [110]. Transparently. The polarized light b enters the pn junction or the pin junction, and electron-hole pairs are generated at the junction. This electron-hole pair is detected as a photocurrent generated by the reverse bias voltage applied to the junction. Based on the above principle,
It becomes possible to selectively receive an optical signal having a polarization component in a specific direction.

[0012]

FIG. 1 shows an example of the structure of a semiconductor photodetector of the present invention. A polarization selection layer 7 having a GaAs / InAs quantum wire periodic structure on an InP substrate 1, an n-type doped InP layer 2, an undoped InGaAs layer 3, and a p-type doped InGaAs layer 4. , AuZ
The n metal electrode 5 is formed. After forming all layers, mesa etching is performed up to the n-type InP layer 2, and then an AuGeNi metal electrode 6 is formed on the n-type InP layer 2. As shown in FIG. 2, the polarization selection layer 7 has a quantum wire periodic structure including a GaAs semiconductor wire 8 and an InAs semiconductor wire 9. Figure 3
Shows the wavelength λ _D , which has the polarization dependence on the transmittance of the polarization selection layer. The polarization selection layer is designed so that the incident light wavelength λ _in and the wavelength λ _D are the same. In the polarization selection layer 7, the polarized light parallel to the quantum wire has a smaller transmittance than the polarized light perpendicular to the quantum wire, so that it becomes possible to selectively receive the input optical signal having the polarization direction perpendicular to the quantum wire. .

In the embodiments described above, the crystal system is I
Although the nGaAsP system is used, other crystal systems may be used, and the composition of the quantum wires in the polarization selection layer and the electrode metal material are not limited to those in the above embodiment.

[0014]

According to the present invention, a semiconductor photodetector that selectively receives light of a specific polarization direction can be easily obtained.

[Brief description of drawings]

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

FIG. 2 is a perspective view showing a polarization selection layer used in the present invention.

FIG. 3 is a diagram illustrating the principle of the present invention.

FIG. 4 is a sectional view showing the structure of a conventional semiconductor photodetector.

[Explanation of symbols]

 1 InP Substrate 2 n-InP Layer 3 i-InGaAs Layer 4 p-InGaAs Layer 5 AuZn Metal Electrode Layer 6 AuGeNi Metal Electrode Layer 7 Polarization Selective Layer 8 GaAs Semiconductor Fine Wire 9 InAs Semiconductor Fine Wire

Claims (2)

[Claims] 1. A p-type semiconductor and n formed on a semiconductor substrate.
A semiconductor photodetector having a pn junction composed of a semiconductor of a type, a second thin semiconductor wire having a first forbidden band width and a second semiconductor thin wire having a first forbidden band width on a light incident surface side of the pn junction. 2. A semiconductor photodetector characterized by having a periodic structure composed of a semiconductor thin wire having a forbidden band width, and having a period such that the periodic structure causes a quantum effect in an in-plane direction. 2. The semiconductor photodetector according to claim 1, further comprising a pin junction formed by forming an i-type semiconductor between the p-type semiconductor and the n-type semiconductor.