JPH1065200A - Infrared radiation detecting element - Google Patents

Abstract

PROBLEM TO BE SOLVED: To enable increasing the photodetection sensitivity wavelength band, in an infrared radiation detecting element using transition in the band of multiple quantum well structure by forming a multiple quantum well light-absorbing layer, wherein quantum well layers of a plurality of kinds of quantum well layer, widths are formed on a substrate. SOLUTION: On a GaAs substrate 8, an n<+> contact layer 7 is formed, on which an electrode 4b and a multiple quantum well light absorbing layer 6 are formed. In the layer 6, quantum well layers of a plurality of kinds of quantum well layer widths are formed. On the layer 6, an n<+> contact layer 5 is formed, on which an electrode 4a is formed. A bias voltage is applied across the electrodes 4a and 4b. In the layer 6, quantum well layers of two kinds of quantum well layer widths are formed, and two kinds of normal energy levels of electrons in the quantum well layer are constituted. Thereby the photodetection sensitivity wavelength band can be widened.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to an infrared light receiving device using an in-band transition of a multiple quantum well structure, and more particularly to an infrared light receiving device capable of broadening a light receiving sensitivity wavelength band.

[0002]

2. Description of the Related Art As a light absorbing layer used in a conventional infrared light receiving element, there is an "HgCdTe layer".
The “Te layer” can detect infrared light in an infrared wavelength region of 3 μm or more.

[0003] However, in the crystal growth of the "HgCdTe layer", techniques such as the vapor phase growth method other than the liquid phase growth method are immature, and even if the "Hg" composition is small even in the liquid phase growth method, There was a problem that it was difficult to control the composition of "HgCdTe".

It is also possible to use the Bridgman method or the like as the "HgCdTe" bulk crystal growth method, but there is a problem that the composition control is difficult due to the difference in the segregation coefficient between "Hg" and "Cd".

[0005] Therefore, in order to improve the difficulty of the above manufacturing method, there is an infrared light receiving element that detects the infrared light by detecting photoexcited electrons generated from the quantum well layer by the infrared light.

FIG. 6 is a sectional view showing an example of such a conventional infrared light receiving element. In FIG. 6, 1 is a window layer, 2 is a multiple quantum well light absorbing layer, 3 is a substrate, 100 is incident light,
1 is a bias voltage.

A multiple quantum well light absorption layer 2 is formed on a substrate 3, and a window layer 1 is formed on the multiple quantum well light absorption layer 2. The incident light 100 enters the multiple quantum well absorption layer 2 via the window layer 1, a bias voltage 101 is applied to the window layer 1, and the substrate 3 is grounded.

Now, the operation of the conventional example shown in FIG. 6 will be described with reference to FIG. FIG. 7 is a band structure diagram showing a state when the bias voltage 101 is applied. In FIG. 7, “A” indicates a quantum well layer, and “B” indicates a conduction band.

Electrons at the ground level of the quantum well layer "a" absorb the incident light 100 and excite the conduction band "b" beyond the discontinuous band existing at the heterojunction interface as shown at "c". Is done.

A bias voltage of 10 is applied to the infrared light receiving element.
Since 1 is applied and an electric field is generated, the electrons excited in the conduction band "b" drift and can be taken out as a current signal as shown in "d".

Further, since the infrared light receiving element shown in FIG. 6 is easy to form, the problem in the case of using the "HgCdTe layer" can be solved. As a result, an infrared light receiving element that can be easily formed and that can detect infrared light can be realized.

[0012]

However, in the conventional example shown in FIG. 6, the quantum state of the electrons in the quantum well layer is a discrete quantum level. The characteristic has a narrow peak near the transition energy from the to the conduction band. In other words, there is a problem in that the light receiving sensitivity wavelength band is narrowed. Accordingly, an object of the present invention is to realize an infrared light receiving element that can broaden a light receiving sensitivity wavelength band in an infrared light receiving element using an in-band transition of a multiple quantum well structure.

[0013]

In order to achieve the above object, an infrared light receiving element for detecting infrared light by detecting photoexcited electrons generated by infrared light from a quantum well layer, the substrate comprising: A multiple quantum well light absorbing layer provided on the substrate and provided with the quantum well layers having a plurality of types of quantum well layer widths; and an electrode for applying a bias voltage to the multiple quantum well light absorbing layer. It is characterized by the following.

According to a second aspect of the present invention, there is provided an infrared light receiving element for detecting the infrared light by detecting photoexcited electrons generated from the quantum well layer by the infrared light.
A multi-quantum well light-absorbing layer formed on the substrate and provided with the quantum well layers of a plurality of compositions; and an electrode for applying a bias voltage to the multi-quantum well light-absorbing layer. It is.

According to a third aspect of the present invention, in the infrared light receiving element for detecting the infrared light by detecting photoexcited electrons generated from the quantum well layer by the infrared light, the substrate comprises:
A multiple quantum well light absorbing layer provided on the substrate and provided with barrier layers of a plurality of compositions separating the quantum well layers from each other; and an electrode for applying a bias voltage to the multiple quantum well light absorbing layer. It is characterized by the following.

[0016]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS The present invention will be described below in detail with reference to the drawings. FIG. 1 is a sectional view showing the configuration of an embodiment of the infrared light receiving element according to the present invention.

In FIG. 1, 4a and 4b are electrodes, 5 and 7 are n ⁺ contact layers, 6 is a multiple quantum well light absorbing layer, 8
Is a GaAs substrate, and 100a is incident light.

An n ⁺ contact layer 7 is formed on a GaAs substrate 8.
Is formed, and the electrode 4b and the multiple quantum well light absorption layer 6 are formed on the n ⁺ contact layer 7, respectively.

An n ⁺ contact layer 5 is formed on the multiple quantum well light absorbing layer 6, and an electrode 4a is formed on the n ⁺ contact layer 5. A bias voltage is applied between the electrodes 4a and 4b by means not shown.

Further, the incident light 100a polarized so that the electric field vector "A" is perpendicular to the stacking direction of the multiple quantum well light absorption layer 6 is incident. For example,
Incident light 100a is obliquely incident from the GaAs substrate 8 side so that the electric field vector "a" is perpendicular to the stacking direction of the multiple quantum well light absorption layer 6.

Here, the embodiment shown in FIG. 1 will be described with reference to FIGS. 2, 3 and 4. FIG. 2 is a band structure diagram showing a state when no bias is applied, FIG. 3 is a band structure diagram showing a state when a bias voltage is applied, and FIG. 4 is a characteristic curve diagram showing an example of a photosensitivity wavelength characteristic.

In FIG. 2, reference numerals 5 and 7 denote the same reference numerals as in FIG. 1. In FIG. 2, "A" indicates a barrier layer, and "B" and "C" indicate quantum well layers.

Further, as shown by "b" and "c" in FIG. 2, there are two types of widths of the quantum well layer.
The ground levels of the electrons in the quantum well layers shown in "b" and "c" are in different states, in other words, the wavelengths of the absorbed infrared light are different.

In this state, when a bias voltage is applied to the infrared light receiving element, a band structure as shown in FIG. 3 is obtained. In FIG. 3, 5 and 7 are denoted by the same reference numerals as in FIG.

When an infrared light having a wavelength "λ1" as shown by "a" in FIG. 3 is incident as the incident light 100a, "in FIG.
Electrons in the quantum well layer indicated by "b" and "c" absorb this infrared light and are excited to the conduction band.

Similarly, the wavelength "d" shown in "d" in FIG.
When the infrared light of λ2 ”is incident as the incident light 100a, the electrons in the quantum well layer indicated by“ e ”and“ f ”in FIG. 3 absorb this infrared light and are excited to the conduction band.

The electrons thus excited in the conduction band drift by an electric field generated by the applied bias voltage and are extracted as current signals from the electrodes 4a and 4b. The relationship between the current signal and the wavelength is shown in FIG. Become like

As can be seen from FIG. 4, the current signal characteristic "A" due to the absorption of infrared light has the wavelength "λ1" shown in "B" in FIG.
It can be seen that the current signal characteristic “c” caused by the above and the current signal characteristic “e” caused by the wavelength “λ2” indicated by “d” in FIG. 4 are superposed.

For this reason, the current signal characteristic "A" due to the absorption of infrared light has a wide light receiving sensitivity wavelength band between the wavelengths "λ2" and "λ1".

As a result, by providing a quantum well layer having two kinds of quantum well layer widths in the quantum well light absorbing layer 6 and using two kinds of ground levels of electrons in the quantum well layer, the light receiving sensitivity wavelength band can be increased. It becomes possible to spread.

In FIGS. 2 and 3, quantum well layers having different quantum well layer widths are sequentially formed after appropriately forming quantum well layers having the same quantum well layer width. However, as shown in FIG. Quantum well layers having different layer widths may be alternately formed.

Further, in the embodiment shown in FIG. 1, two types of quantum well layer widths are used. However, if the type of the quantum well layer width is made larger, it is possible to further widen the light receiving sensitivity wavelength band.

For example, the wavelengths “λ1”, “λ2” to “λ”
By forming the quantum well layer width so as to correspond to n ″, the light receiving sensitivity wavelength band can be broadened.

In the embodiment shown in FIG. 1, the ground level of electrons in the quantum well layer is changed by changing the width of the quantum well layer of the quantum well light absorbing layer 6, but the composition of the quantum well layer is changed. Alternatively, by changing the composition of the barrier layer,
The ground level of the electrons in the quantum well layer may be changed.

The multiple quantum well structure is described as “AlGaAs
/ GaAs "," AlGaAs / InGaAs ", and" InGaAsP / InP "can be easily formed.

In the embodiment shown in FIG. 1, the GaAs substrate 8 is used.
It is also possible to manufacture an infrared light receiving element by forming a multi quantum well structure or the like.

[0037]

As is apparent from the above description,
According to the present invention, the following effects can be obtained. By providing a quantum well layer having two types of quantum well layer widths in the quantum well light absorption layer and using two types of ground levels of electrons in the quantum well layer, infrared light can broaden the wavelength band of light sensitivity. A light receiving element can be realized.

[Brief description of the drawings]

FIG. 1 is a sectional view showing the configuration of an embodiment of an infrared light receiving element according to the present invention.

FIG. 2 is a band structure diagram showing a state without bias.

FIG. 3 is a band structure diagram showing a state when a bias voltage is applied.

FIG. 4 is a characteristic curve diagram showing an example of a photosensitivity wavelength characteristic.

FIG. 5 is a band structure diagram showing a state without bias.

FIG. 6 is a sectional view showing an example of such a conventional infrared light receiving element.

FIG. 7 is a band structure diagram showing a state when a bias voltage is applied.

[Explanation of symbols]

DESCRIPTION OF SYMBOLS 1 Window layer 2, 6 Multiple quantum well light absorption layer 3 Substrate 4a, 4b Electrode 5, 7n ⁺ contact layer 8 GaAs substrate 100, 100a Incident light 101 Bias voltage

Claims (3)

[Claims] 1. An infrared light receiving element for detecting infrared light by detecting photoexcited electrons from a quantum well layer generated by infrared light, comprising: a substrate; and a plurality of types of quantum well layers formed on the substrate. An infrared light receiving element comprising: a multiple quantum well light absorption layer provided with the quantum well layer having a width; and an electrode for applying a bias voltage to the multiple quantum well light absorption layer. 2. An infrared light-receiving element for detecting infrared light by detecting photoexcited electrons from a quantum well layer generated by infrared light, comprising: a substrate; and a plurality of types of compositions formed on the substrate. An infrared light receiving element comprising: a multiple quantum well light absorbing layer provided with a quantum well layer; and an electrode for applying a bias voltage to the multiple quantum well light absorbing layer. 3. An infrared light receiving element for detecting infrared light by detecting photoexcited electrons from a quantum well layer generated by infrared light, comprising: a substrate; and a quantum well layer formed on the substrate. An infrared light receiving element comprising: a multiple quantum well light absorption layer provided with barrier layers of a plurality of types of compositions separating the electrodes; and an electrode for applying a bias voltage to the multiple quantum well light absorption layer.