JPS58193B2 - Semiconductor optical detection device - Google Patents

Description

[Detailed description of the invention] The present invention relates to a semiconductor optical detection device.

PIN photodiode as a semiconductor optical detection device.

There are avalanche photodiodes, phototransistors, etc., but PIN photodiodes have the advantage of having a simple structure and being easy to manufacture, but since they do not have an amplification effect, they have a detection output that has a large gain by itself. Moreover, avalanche photodiodes have the opposite advantages and disadvantages to PIN photodiodes, and also have the disadvantage of requiring a particularly harsh usage environment.Furthermore, phototransistors are relatively Although a detection output can be obtained with a large gain, it has the disadvantage of slow response speed.

Furthermore, a structure in which a diode is connected between the base and collector of an npn transistor has been proposed, as shown in a cross-sectional view in FIG. 1 and an equivalent circuit diagram in FIG.

(Japanese Unexamined Patent Publication No. 53-71590) However, even with this type of structured device, the optical detection characteristics have the disadvantage that they can be used only up to a certain frequency, as shown in the part A in Figure 3. had.

The present invention solves these drawbacks and proposes an apparatus suitable for high-frequency optical detection and wave detection.

That is, the present inventors believe that the skirt pull shown in FIG. 3 is caused by the recombination of minority carriers, and by introducing impurities that form deep levels that promote recombination,
This is to prevent the hem from pulling.

The present invention will be described in detail below using the drawings. FIG. 4 shows an example of a semiconductor optical detection device according to the present invention, which is designated as a whole by M, and includes, for example, an N-type semiconductor layer 1, an N-type semiconductor layer 2 formed on this layer 1, and this layer. 2, P-type semiconductor regions 3 and 4 are formed from the side opposite to the layer 1 side with a required spacing between them; N-type semiconductor regions 5 and 6
and terminals 7 and 8 led out from layer 1 and region 6, respectively.

In such a configuration, layers 1 and 2 and region 3 are used to form a P layer, with layer 1 being an N layer, layer 2 being a 1 layer, and region 3 being a P layer.
IN photodiode H is also located in layers 1 and 2 and region 3.
and 5 form an NPN transistor T1 having layers 1 and 2 as collector, region 3 as base, and region 5 as emitter.
This structure is the same as the conventionally known structure shown in FIG.

Furthermore, it is clear that in the present invention, layers 1 and 2 and regions 4 and 6 constitute an NPN transistor T2 in which layers 1 and 2 are collectors, region 4 is a base, and region 6 is an emitter. be.

Further, a region 5 constituting the emitter of the NPN transistor T1 is connected to a region 4 constituting the base of the NPN transistor T2 via a wiring 9, while the transistor T1
The collectors of T2 and T2 are constructed of layers 1 and 2 common to them, and thus have two transistors having a common collector region, and the base regions of these transistors are in the collector. The so-called Darlington connection circuits provided are also known from the prior art.

(Japanese Patent Publication No. 53-10434) The present invention differs from these conventional devices in that an impurity is introduced into the layer 2 to form a deep level.

This impurity is for compensating the carrier concentration and making the carrier concentration of layer 2 sufficiently low.

Furthermore, layer 2 is formed on layer 1 as a substrate by, for example, epitaxial growth.
and is selected to be sufficiently large compared to the specific resistance of layer 3,
The thickness D2 under layer 3 is chosen to be greater than the characteristic absorption length of layer 2 for light.

Moreover, in order to perform optical detection under quantitative conditions, layer 3 is obtained by impurity diffusion into layer 2, but the thickness D3 of layer 3 is less than 1/10 of the characteristic absorption length of layer 3 for light. The layer 4 is preferably obtained by diffusion of impurities into the layer 3, and the area of the layer 4 when viewed from the side on which the light is incident is selected to be 115 or less of the area of the layer 3 when viewed from the same side. It is preferable that the

FIG. 5 is a photodetection waveform diagram showing the effect of introducing an impurity that forms a deep level.

The optical detection device used had the following configuration.

Layer 1: n-type Si substrate with specific resistance 0.015 Ωcm Layer 2: n-type epitaxial growth layer with specific resistance 132 Ωcm, thickness 43 μm Layer 3: Doped with BN at 1000°C for 30 minutes, 1000°C
P-type region of Bdope, 1μ thick, driven for 90 minutes with
m, main surface is 265 μmφ circular layer 4: N + type region doped with P at 950° C. for 40 minutes thickness 0.5 μm, main surface is 50 μmφ circular deep level Forming impurity is Au in 02 atmosphere Diffusion was performed at 850°C for 20 minutes.

Furthermore, the irradiation light is pulsed light with a wavelength of 0.85 μm and a pulse width of about 0.5 ns.

The photodetection waveform shown in FIG. 3 uses the above-described configuration except that Au is not diffused as a photodetection device, and the irradiation light is also the same as that described above.

From FIG. 5, it is clear that the optical detection device of the present invention does not exhibit any skirting as shown by A in FIG.

FIG. 6 is a diagram showing the dependence of recovery time on the amount of Au doping.

The recovery time is directly related to the recombination time of minority carriers, and the forward voltage of the PN junction formed by layers 2 and 3 between electrode 7 and the electrode connected to layer 3 or layer 4 is In addition, when switching to the reverse voltage, it is the time from when the voltage is switched to the reverse voltage until the forward current flowing due to minority carriers remaining without recombination disappears.

When measuring Figure 6, the peak current value (current value when forward voltage was applied) was obtained when a forward voltage of 0.5V was applied and the voltage was switched to -4.0V. is 1/10
It shows the time when

In Figure 6, the doping amount was not changed, but the diffusion time was kept constant (20
(min)) It shows the dependence on the doping temperature, but since there is a relationship that the doping amount increases as the doping temperature increases, it shows the doping amount dependence.

Note that the values indicated by the dotted line in FIG. 6 are the values when Au is not doped.

As explained with reference to FIGS. 5 and 6, it is clear that the apparatus of the present invention is a significant improvement over the conventional apparatus with respect to high-frequency optical detection.

As described above, the semiconductor optical detection device according to the present invention described above can function as a photodetection device, and since the specific resistance of layer 2 is selected to be sufficiently large compared to that of region 3,
The depletion layer obtained by expanding to both sides of the PN junction 10 is obtained by largely expanding to the layer 2 side, and on the other hand, the thickness of the layer 2 is larger than the characteristic absorption length of the layer 2 for light at the thickness below the layer 3. Since the thickness of the depletion layer expanded to the layer 2 side can be made larger than the characteristic absorption length of layer 2 for light, it is possible to prevent the incident light from becoming electric carriers within the depletion layer. The conversion is done with great efficiency.

This also means that if the thickness of the region 3 is selected to be 1/10 or less of the characteristic absorption length of the region 3 for light, light can efficiently enter the depletion layer that extends through the region 3 toward the layer 2 side. This is even more so since the area of region 5 is viewed from the side where the light enters and the area of region 3 is 11 when viewed from the same side.
This is especially true if the value is selected to be 5 or less, since the presence of the region 4 does not reduce the problem of light incident on the depletion layer, which passes through the region 3 and widely spreads toward the layer 2 side.

In addition, the incident light is converted into electrical carriers with high conversion efficiency, and the current based on it is P.
The output current obtained as the IN photodiode H is amplified by the NPN transistors T1 and T2, and the amplified output current becomes the output current of the device M, so the detection output of the incident light is efficiently It has the characteristic that it can be obtained with a good and large gain.

Furthermore, since an impurity is introduced into layer 2 to form a deep level to compensate for the carrier concentration, recombination of minority carriers is promoted in layer 2 as described above, making it difficult to increase the frequency. It has the characteristics of being

Moreover, transistor T1. As is clear from the above, the conversion of incident light into electric carriers in T2 is mainly performed on the layer 2 side as the collector, not in the region 3 as the base of the transistor T1. The transistor T2 responds at a high speed according to the incident light, and of course the transistor T2 responds at a high speed. It has the characteristic that a detection output that responds quickly can be obtained.

Furthermore, according to the semiconductor optical detection device M according to the present invention described above, a configuration in which a plurality of the devices (hereinafter referred to as Ml, M2, etc.) can be used as an imaging device in which they are arranged side by side can be extremely easily constructed. It can be configured.

That is, although a detailed explanation will be omitted, one of the layers 1 is connected to the device M.
12M2..., and one of the layers 2 is also commonly used for the devices M12M2..., it is possible to easily obtain a configuration in which a plurality of devices M are arranged side by side. In this case, even if the layer 2 for the husband and wife of the devices M12M2, etc. is common, a depletion layer is generated in the layer 2 at the position where each device is formed when each device is operated, so this causes mutual interference. It has the feature that adjacent devices can be electrically isolated from each other without using any special means.

Furthermore, according to the semiconductor optical detection device M according to the present invention described above, as shown in FIG. 15, and further connect one end of the region 14 to the region 4 using a wiring 16.
and 5, and the other end is connected to the region 15 using a wiring 17, and a common region 14 is provided between the collector and emitter of the transistor T1 and between the base and collector of the transistor T2. Since a configuration in which the resistors are connected is obtained, this configuration has great features such as improving the response operation of the Darlington connection circuit formed by the transistors T1 and T2.

It should be noted that the above description is merely an example of the present invention, and the above-mentioned "P type" may be replaced with "N type", "N type" may be replaced with "P type", and various other configurations may also be used. Variations may be made.

[Brief explanation of the drawing]

Fig. 1 is a sectional view of a conventional optical detection device, Fig. 2 is an equivalent circuit diagram of Fig. 1, Fig. 3 is an optical pulse detection characteristic diagram of the device shown in Figs. 1 and 2, and Fig. 4 5 is a line sectional view showing an example of the semiconductor optical detection device of the present invention, FIG. 5 is a diagram of the optical pulse detection characteristics of the device of the present invention shown in FIG. 4, and FIG. 6 is a diagram showing the doping amount dependence of recovery time. The figure shown in FIG. 7 is a line sectional view showing an example of application of the semiconductor optical detection device according to the present invention. In the figure, M, Ml, M2... are semiconductor optical detection devices, L is light, H is PIN photodiode, T1 and T2
is an NPN transistor, 1 and 2 are semiconductor layers, 3.4
, 5, 6, 14 and 15 are semiconductor regions, 7 and 8 are terminals, and 9 and 17 are wirings, respectively.

Claims (1)

[Claims] 1 a first semiconductor layer having a first conductivity type; a second semiconductor layer having the first conductivity type formed on the first semiconductor layer; first and second semiconductor regions having a second conductivity type opposite to the first conductivity type formed from the side opposite to the first semiconductor layer side; and inside the first and second semiconductor regions. third and fourth semiconductor regions having a first conductivity type formed from the side opposite to the first semiconductor layer side, and lead-out from the first semiconductor layer and the fourth semiconductor region, respectively. the second semiconductor layer has a specific resistance selected to be larger than that of the first semiconductor layer and the first semiconductor region; The thickness below the semiconductor region is such that light is incident on the second semiconductor layer through the first semiconductor region from the side opposite to the first semiconductor layer side of the first semiconductor region. the second and third semiconductor regions are connected to each other, and a deep level is formed in the second semiconductor layer to compensate for its carrier concentration. A semiconductor optical detection device characterized in that impurities that form are introduced.