JPS62183570A - Photodetector - Google Patents

Abstract

PURPOSE:To form a serrated periodic potential barrier, to separate spatially a photocurrent consisting of electrons and holes subjected to photoexcitation, and also, to carrier-transport these separated photocurrents in a two-dimensional electron gas layer by forming the two-dimensional electron gas layer into a multilayer periodic structure consisting of planar doped N-type layers and planar doped P-type layers. CONSTITUTION:Planar doped N-type layers 13 and planar doped N-type layers 14 are in this semiconductor epitaxial layer 12 and are ones doped an N-type dopant and a P-type dopant to the respective N-type and P-type layers in such a way that the N-type and P-type layers are alternately formed in a periodic structure and laminated within the range of one atomic layer or several atomic layers and at the carrier concentration of 10<12>-10<13>cm<-2>. In case a periodic structure consisting of the planar doped N-type layers 13 and the planar doped P-type layers 14 is formed in the low-carrier concentration semiconductor epitaxial layer 12 which is used as a photoabsorption region, the energy level between the lower end of the conduction band and the upper end of the valence band becomes of a serrate state to form a periodic potential barrier.

Description

DETAILED DESCRIPTION OF THE INVENTION [Industrial Application Field] The present invention relates to a photodetection device, and more particularly to an improved structure of a photodetection device comprising a semiconductor light receiving element for converting an optical signal into an electrical signal.

[Conventional technology]

In general, as representative examples of light receiving elements using this type of semiconductor, the configurations of a PIN photodiode and an avalanche photodiode are well known, and there is also a photodetecting device using a doped superlattice.

FIG. 4 and FIG. 5 first schematically show the general configurations of a PIN photodiode and an avalanche photodiode according to these conventional examples, respectively.

That is, in the PIN photodiode shown in FIG. 4, reference numeral 21 denotes a p-layer with a low carrier concentration (p-type semiconductor substrate), and numeral 22 selectively forms a p-n junction on one main surface of the p-layer. One layer with high carrier concentration to be formed, 23
is a p layer with high carrier concentration provided on the other main surface of the p layer.
25 and 28 are electrodes for current detection, respectively, and 27 is an insulating layer.

Further, in the avalanche photodiode shown in FIG. 5, reference numeral 24 is a p layer provided between the p layer 21 and the n+ layer 22, and the other structure is exactly the same as the previous example.

In the case of the PIN photodiode having the configuration shown in FIG. 4, a reverse bias is applied between the P layer 21 and the N+ layer 22 to form a depletion layer over the entire region of the P layer 21, and in this region, Electrons and holes that are photoexcited by light incident on the n+ layer 22 are transferred to the n+ layer 22 and the p+ layer 23.
In addition, in the case of the avalanche photodiode with the configuration shown in FIG. The photocurrent is amplified by an avalanche multiplication mechanism in the high electric field region formed between the photocurrents and detected as a larger photocurrent.

Further, FIG. 6 shows a photodetector using a doped superlattice structure.

In FIG. 6, reference numeral 31 denotes a semiconductor substrate, 32 and 33 a light receiving area on this substrate 31, and a thickness of several hundred and fifty-fifty.
N-layers and p-layers are alternately stacked to form a periodic structure, and 34.34 indicates a doped layer with a high carrier concentration, one of which is n-type and the other is p-type, and the n-layer 32 and the two layers are 33, ohmic connections are established between each of these layers.

In the case of this element configuration, the first layer 32 and the second layer 3
Due to the periodic structure of 3, the potential distribution between the lower end of the conduction band and the upper end of the valence band near the band gap shows a sinusoidal shape as shown in the band diagram in Figure 7, and when there is such a potential barrier, , quantum levels 35 and 35 are formed at the bottom of the conduction band and valence band, respectively, and electronic transitions between these quantum levels 35 become possible, allowing light to be received with energy smaller than the band gap. It can be done.

[Problem that the invention seeks to solve]

Here, in conventional photodetecting devices represented by the PIN photodiode and avalanche photodiode shown in FIGS. 4 and 5, in order to obtain steep photoresponse characteristics, light absorption is Electrons and holes are generated mainly in the depletion layer caused by the junction and are accelerated in the reverse biased pn junction region. In this case, the thickness of the depletion layer is as follows: It is necessary to optimize the design according to the applied crystal material and the wavelength of the incident light, and on the other hand, in order to keep the capacitance of the device itself to a smaller value, the thickness of this depletion layer is usually set from several ILm to several tens of ILm. IL
This result is set to a range of m.

There is a problem in that it is difficult to integrate these PIN photodiodes and avalanche photodiodes with other electronic photodiodes, and in the case of the conventional photodetector shown in FIG. However, there was a problem in that the donor ions in the n-layer were screened by photoexcited electrons, resulting in the potential region between the n-layer and p-layer becoming dull.

This invention was made in order to improve such problems in the conventional device, and its purpose is to have high photodetection sensitivity and photoresponse characteristics, and also to provide high photodetection sensitivity and photoresponse characteristics. The object of the present invention is to obtain a photodetecting device that can be integrally integrated with a red light element.

[Means for solving problems]

In order to achieve the above object, the photodetection device according to the present invention includes a multilayer periodic structure of alternating thinly planar-doped n-layers and p-layers in an n-type or p-type semiconductor layer with a low carrier concentration as a light absorption region. A highly doped p-type or n-type layer is formed through each of these n-layers and p-layers to form an ohmic contact with each electrode.

[For production]

Therefore, in this invention, a sawtooth periodic potential barrier is formed by the multilayer periodic structure of the planar-doped n-layer and p-layer, and the photocurrent caused by photoexcited electrons and holes can be spatially separated. , and these can be transported as carriers within the two-dimensional electron gas layer.

〔Example〕

Hereinafter, one embodiment of the photodetecting device according to the present invention will be described in detail with reference to FIGS. 1 to 3.

FIG. 1 is a perspective view showing the general configuration of a photodetecting device according to this embodiment. In this FIG. 1 embodiment configuration, reference numeral 1
1 is a semiconductor substrate, 12 is a semiconductor epitaxial layer with a low carrier concentration as a light absorption region grown on this semiconductor substrate 11, and 13 and 14 are in this semiconductor epitaxial layer 12, each having one to several atomic layers. range, sheet carrier density is 1 to 1013c+
A planar-doped n-layer and a planar-doped double layer doped with n-type and p-type dopants are stacked alternately to form a periodic structure.
5.15 is a doped layer with a high carrier concentration formed through each of these layers 13.14 to form an ohmic contact with the electrodes to, te, respectively, in which the semiconductor epitaxial layer 12 is formed with an n layer with a low carrier concentration. −
If the former is a p-type, an n-type dopant is used in these heavily doped layers 15.15, and conversely, if the former is a p-type, a p-type dopant is used in the latter.

Therefore, when a periodic structure of a planar-doped first layer 13 and a second layer 14 is formed in the semiconductor epitaxial layer 12 with a low carrier concentration, which serves as a light absorption region, as in the configuration of this embodiment, the lower end of the conduction band and The energy level with respect to the upper end of the valence band has a sawtooth shape as shown in FIG. 2, forming a periodic potential barrier.

Here, the height V of the potential barrier measured from the lower end of the conduction band mentioned above is given by the following equation. Namely.

V = g-NDd/2 ε ・°・Glance: elementary quantity of electricity.

ND: Donor doping concentration.

d: Distance between planar doped n-layer and p-layer.

ε: dielectric constant of semiconductor epitaxial layer.

It is.

Now, if the semiconductor epitaxial layer 12 is GaAs (gallium arsenide), ND=2X 1012 cm-2,
When d = too, V = 0.58 (V), and if there is such a potential barrier, there will be quantum levels 17 and 1? at the bottom of the conduction band and valence band, respectively. is formed,
This quantum level 17.1? The occupied electrons form a two-dimensional electron gas layer - and the electrons within this periodic potential barrier region are excited by absorbing light with energy greater than the band gap. and holes are diffused and spatially separated at the bottom of the triangular potential well due to the potential barrier, which reduces the probability of electron-hole recombination and increases and improves quantum efficiency. be able to.

For example, in the configuration of this embodiment, the electrode te
, te interval to l0JL11. When the bias voltage is IOV, the electric field strength in the in-plane direction in the semiconductor epitaxial layer 12 is 10'V/c■, and the drift speed at this electric field strength corresponds to the saturation speed region.
The saturation velocity of the two-dimensional electron gas layer is on the order of 106 to 1070■/SeC, and therefore, in the photodetector according to the configuration of this embodiment, the photocurrent due to electrons and holes is Since each carrier is transported within a two-dimensional electron gas layer, carriers are transported at a high speed, and higher photodetection sensitivity and photoresponse characteristics can be expected when compared to conventional examples. Since the direction of photocurrent is in-plane and the light absorption region and carrier transport region are in the same region, the device structure can be made smaller and can be integrated with other electronic/optical devices. This makes integration possible.

In the above embodiment, the structure of each planar-doped layer is a multilayer periodic structure of 11+P+11+...n, but a multilayer periodic structure of P+n+P+, old..., p is also applicable. Of course, the highly doped layer for making ohmic contact with each electrode may be formed by ion implantation, and each electrode may be formed in a comb-like shape as shown in Figure 3. form,
Even if a highly doped layer is disposed below the layer, similar actions and effects can be obtained.

〔Effect of the invention〕

As detailed above, according to the present invention, a multilayer periodic structure of alternating and thinly planar-doped n layers and p layers is formed in a semiconductor layer with a low carrier concentration as a light absorption region. The periodic structure allows the formation of saw-tooth periodic potential barriers and, in turn, multiple two-dimensional electron gas layers to enable carrier transport, which enables highly efficient and fast-response photodetection, and also improves the device structure. It can exhibit excellent features such as miniaturization and integral integration with other electronic/optical devices.

[Brief Description of the Drawings] Fig. 1 is a perspective view schematically showing the general configuration of an embodiment of the photodetecting device according to the present invention, Fig. 2 is a band diagram of the above, and Fig. 3 is an arrangement of the above electrodes. FIGS. 4 and 5 are perspective views showing the configuration separately; FIGS. 4 and 5 are cross-sectional views schematically showing the general configurations of a PIN photodiode and an avalanche photodiode as conventional photodetecting devices; and FIG. A seventh perspective view schematically showing the general configuration of a photodetection device using a doped superlattice structure in an example.
The figure is a band diagram of the same as above. DESCRIPTION OF SYMBOLS 11... Semiconductor substrate, 12... Semiconductor epitaxial layer with low carrier concentration, 13... Planar doped n layer, 14... Planar doped two layer, 15...
- Highly doped layer, 16...electrode, 17...quantum level. Agent Masuo Oiwa Figure 4 Figure 5 ♂〉41 Figure 6 Figure 7

Claims (5)

[Claims] (1) A planar-doped n-layer and a planar-doped p-type semiconductor layer with a multilayer periodic structure in which n-type and p-type dopants are alternately and thinly planar-doped into an n-type or p-type semiconductor layer with a low carrier concentration as a light absorption region. layer, and a highly doped layer that forms ohmic contact with the electrode through each of these n-layers and p-layers, and the sawtooth periodic potential barrier of the multilayer periodic structure allows photoexcited electrons and positive 1. A photodetection device characterized in that photocurrents caused by holes are spatially separated and these can be transported as carriers within a two-dimensional electron gas layer. (2) Planar doped n layer and planar doped p layer,
Each has a range of one to several atomic layers, and a sheet carrier concentration of 10^1^2 to 10^1^3 cm^-^2
2. The photodetecting device according to claim 1, wherein the photodetecting device is formed to have the following properties. (3) The multilayer periodic structure of each planar doped layer is defined as n, p,
The photodetecting device according to claim 1, characterized in that the photodetecting device is formed in the order of n, p, . . . , n type. (4) The multilayer periodic structure of each planar doped layer is p, n,
The photodetecting device according to claim 1, characterized in that p, n, . . . , p-types are formed in this order. (5) The photodetecting device according to claim 1, wherein the highly doped layer is selectively diffused and formed by ion implantation.