JPH04367282A - Semiconductor photodetector - Google Patents

Abstract

PURPOSE:To provide a semiconductor photodetector provided with a photoabsorption layer of a high-sensitivity superlattice structure. CONSTITUTION:A semiconductor photodetector 1 is constituted into a structure wherein an N<+> GaAs electrode layer 3, a GaAs/AlGaAs superlattice layer 4 and an N<+> GaAs electrode layer 5 are laminated on a semiconductor substrate 2 and metal electrodes 3a and 5a are respectively provided on the surfaces of the layers 3 and 5. End surfaces of the superlattice layer 4 are respectively formed into bevel surfaces 4a by a wet etching using a phosphoric acid and ammonia or a dry etching using plasma and a metal reflection film 7 is provided on the outer sides of these bevel surfaces 4a via an insulator layer 6 to transmit infrared rays.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a monolithic semiconductor photodetector having a photodetector having a superlattice structure.

0002

[Prior Art] Pyroelectric sensors and semiconductor sensors have been known as photodetectors for infrared rays, etc. The former has low sensitivity and is difficult to integrate, so it is used as a single sensor, while the latter Semiconductor type sensors are used as image sensors.

[0003] Semiconductor type sensors further include a monolithic type that uses a silicon Schottky diode as a sensor, and a monolithic type that uses a silicon Schottky diode as a sensor, and a type that uses indium antimony (InSb), mercury, cadmium,
There are two main types: a hybrid type that uses tellurium (HgCdTe) as a sensor and a silicon CCD or the like as a scanning circuit. Among the semiconductor type sensors mentioned above, the monolithic type has low light detection sensitivity and there is little freedom in designing the spectral sensitivity. On the other hand, although the hybrid type has high sensitivity, it
There are issues with e integration technology.

[0004] Therefore, an infrared detector with a superlattice structure using a gallium-arsenic (GaAs)-based compound, which has more advanced integration technology than InSb or HgCdTe, was proposed in Japanese Patent Laid-Open No. 63-24.
It has been proposed as No. 6626. As shown in FIG. 4, this detector has an n-type semiconductor electrode layer 10 on a semiconductor substrate 100.
1, a semiconductor heterostructure superlattice 102 that absorbs infrared rays is formed on this electrode layer 101, and an n-type semiconductor electrode layer 103 is further formed on the superlattice 102.

By the way, FIG. 3 shows the angle of light incident on the superlattice, and the relationship between the incident angle and the light absorption rate can be expressed by the following (Equation 1).

[0006]

[Math 1]

As is clear from the above equation, the light absorption rate between subbands formed in the superlattice increases as the incident angle approaches 90°, in other words, the more parallel it is to the superlattice. becomes higher. Therefore, in the conventional example shown in FIG. 4, the end face of the semiconductor substrate 100 is processed to be inclined. Further, as shown in FIG. 5, a technique is also known in which the surface of the n-type semiconductor electrode layer 103 on the incident side is processed into a sawtooth shape so that the incident angle is oblique.

[0008]

[Problems to be Solved by the Invention] As mentioned above, in order to obtain a monolithic semiconductor photodetector with high sensitivity, it is possible to make the light absorption layer have a superlattice structure, but the conventional structure It is not possible to make the angle of incidence of light on the light absorption portion of the grating structure close to 90°.

[0009]

Means for Solving the Problems In order to solve the above-mentioned problems, the present invention provides a semiconductor photodetection device in which a photodetection section with a superlattice structure is formed on a semiconductor substrate, wherein the end face of the photodetection section is an inclined surface, A reflective film was formed on the outside of this inclined surface to allow light from the outside to enter at an angle substantially parallel to the superlattice.

0010

[Operation] When light such as infrared rays is incident on the superlattice, electrons are excited from subbands in the superlattice, and the excited electrons escape from the wells to generate current.

[0011]

DESCRIPTION OF THE PREFERRED EMBODIMENTS Examples of the present invention will be described below with reference to the accompanying drawings. Here, FIG. 1 is a sectional view showing an example of a semiconductor photodetection device according to the present invention.

The semiconductor photodetector 1 has an n+ type GaAs electrode layer 3, a GaAs/AlGaAs superlattice 4, and an n+ type GaAs electrode layer 5 stacked on a semiconductor substrate 2.
Metal electrodes 3a, 5a are provided on the surfaces of the As electrode layers 3, 5.

[0013] The superlattice 4 is formed by molecular beam epitaxy (MBE).
It is formed by an epitaxial growth method with high film thickness controllability, such as metal organic vapor phase epitaxy (MOVPE), and its period is several tens to hundreds of angstroms.

Further, the superlattice 4 has an inclined surface 4a at its end face by wet etching using phosphoric acid or ammonia or dry etching using plasma, and metal reflection is formed on the outside of this inclined surface 4a via an insulating layer 6 that transmits infrared rays. Membrane 7
has been established.

The infrared rays incident from the semiconductor substrate 2 side are reflected by the reflective film 7 and incident on the superlattice 4 at an angle substantially parallel to the superlattice 4. When light such as infrared rays is incident on the superlattice 4, electrons are efficiently excited, and the excited electrons escape from the wells to generate current.

FIG. 2 shows another embodiment, in which a collector-up heterostructure bipolar transistor 10 as a signal transfer switch is integrally formed on the semiconductor photodetector 1. There is. This bipolar transistor 10 also uses the n+ type GaAs electrode layer 5 as an emitter, and has an n
type AlGaAs heteroemitter 11, p-type GaAs base 12, n-type GaAs collector 13, and n+ type GaAs
A collector 14 is formed.

By periodically turning on and off the current flowing through the base electrode of the bipolar transistor 10 formed on the photodetecting device 1 having the superlattice structure, the light incident on the photodetecting section having the superlattice structure can be detected. can be sequentially extracted as electrical signals.

Furthermore, if a bipolar transistor is provided on a semiconductor photodetector device in which the end face of the superlattice is a sloped surface, as in the semiconductor photodetector device according to the present invention, the sloped region can be used as an element isolation region or a wiring region. This makes it possible to achieve even higher integration.

In the embodiment, an example of detecting infrared rays was shown, but it may also be possible to detect visible light, etc. Also, although a diode with an n+nn+ structure is shown as the photodetecting section, pin
It may have a p+ip+ structure or a p+pp+ structure. Furthermore, the light incident surface of the semiconductor substrate or electrode layer may be processed into a sawtooth shape as in the conventional method.

[0020]

[Effects of the Invention] As explained above, according to the present invention,
Since the end face of the photodetecting part of the superlattice structure is an inclined surface and a reflective film is formed on the outside of this inclined surface, light from the outside can be made to enter at an angle approximately parallel to the superlattice, and the light absorption rate can be reduced. It is possible to obtain a monolithic photodetection device with significant improvement and high sensitivity, and furthermore, by using this photodetection device, a highly sensitive and highly integrated image sensor can be constructed.

[Brief explanation of drawings]

FIG. 1 is a cross-sectional view of a semiconductor photodetection device according to the present invention.

[Figure 2
]A cross-sectional view of a semiconductor device in which a semiconductor photodetection device according to the present invention is integrally incorporated.

[Figure 3] Diagram showing the relationship between the superlattice and the incident angle of light

[Figure 4]
Cross-sectional view showing conventional structure

[Figure 5] Cross-sectional view showing conventional structure

[Explanation of symbols]

1... Semiconductor photodetector, 2... Semiconductor substrate, 3, 5... n+
type GaAs electrode layer, 4... superlattice, 7... reflective film, 10... bipolar transistor.

Claims (1)

[Claims] 1. A semiconductor photodetecting device in which a superlattice-structured photodetecting section is stacked on a semiconductor substrate, wherein an end surface of the photodetecting section is an inclined surface, and an external light source is formed on the outside of the inclined surface. A semiconductor photodetection device characterized in that a reflective film is formed that allows the light to be incident at an angle substantially parallel to the superlattice.