JPH0992930A - Semiconductor device - Google Patents

Abstract

PROBLEM TO BE SOLVED: To provide a semiconductor device having an electrode on a conductivity type semiconductor layer which is capable of good ohmic contact and excellent in crystallinity. SOLUTION: This semiconductor device has a P-type side electrode on a P-type semiconductor layer composed of II-IV group compound semiconductor which contains Zn and Se. The P-type semiconductor layer 7 has nitrogen containing region films 8 whose acceptor concentration is greater than that of the P-type semiconductor layer 7, in the vicinity of the P-type side electrode 9 side.

Description

Detailed Description of the Invention

[0001]

TECHNICAL FIELD The present invention includes Zn and Se.
The present invention relates to a semiconductor device having a p-type side electrode on a p-type semiconductor layer made of a II-VI group compound semiconductor.

[0002]

2. Description of the Related Art ZnS having a wide bandgap of direct transition type
Since II-VI group compound semiconductors such as e, ZnSSe, and MgZnSSe are capable of emitting light in the bands from ultraviolet light to blue and green, active research has been conducted mainly as a material for light emitting devices.

However, by simply forming an electrode made of Au, Pt, or the like on the p-type II-VI group compound semiconductor layer (contact layer) containing Zn and Se as described above, ohmic contact with good characteristics can be obtained. Is hard to get.

This is because it is difficult to manufacture the above material system so that the acceptor concentration exceeds 1 × 10 ¹⁸ cm ^-3 .

That is, in such a material system, since the p-type contact layer cannot have a high concentration of acceptor,
When the type contact layer is ZnSe, there is an energy barrier of about 0.75 eV in the valence band between the contact layer and the electrode. As a result, a high resistance depletion layer is formed in the vicinity of the surface of the p-type ZnSe contact layer, which prevents ohmic contact.

As a method for solving this problem, for example, in Japanese Utility Model Application Laid-Open No. 63-191657 (H01L 33/00), p-type ZnSe is formed on a p-type ZnSe contact layer.
Superlattice structure layer composed of a film / p-type ZnTe film and p-type Z
A configuration has been proposed in which an nTe layer is formed in this order, and an Au electrode is formed on the p-type ZnTe layer.

As another method, on the p-type ZnSe layer or the p-type ZnTe layer, a semi-metal HgSe layer is interposed and A
A configuration for forming a u electrode has been proposed.

[0008]

However, in the first method, it is necessary to accurately control the film thickness of each film forming the superlattice structure layer, but it is difficult to perform this control with good reproducibility. Is.

Further, in a semiconductor device represented by a light emitting element using a II-VI group compound semiconductor, a GaAs single crystal substrate is generally used as a substrate, and a II-VI group compound semiconductor is lattice-matched with the GaAs substrate. The layer is crystallized. However, the ZnTe crystal has a remarkably large lattice mismatch with the GaAs crystal. For this reason, it is difficult to obtain a good semiconductor crystal, such as dislocation occurring in the crystal in the semiconductor device, and device resistance, that is, power consumption may increase.

Further, the second method has a problem that it is difficult to grow crystals because mercury has a high vapor pressure.

The present invention has been made in view of the above problems, and Z having good ohmic contact and good crystallinity can be obtained.
An object of the present invention is to provide a semiconductor device having a p-type side electrode on a p-type semiconductor layer made of a II-VI group compound semiconductor containing n and Se.

[0012]

According to the present invention, there is provided a semiconductor device comprising:
A semiconductor device having a p-type side electrode on a p-type semiconductor layer made of a II-VI group compound semiconductor containing Zn and Se, comprising:
The p-type semiconductor layer has a nitrogen-containing region film having an acceptor concentration higher than that of the p-type semiconductor layer in the vicinity of the p-type side electrode side.

In particular, the distance between the p-type side electrode and the nitrogen-containing region film is 26 Å or less.

Further, the p-type semiconductor layer has a nitrogen-containing region film having an acceptor concentration higher than that of the p-type semiconductor layer, in addition to the vicinity of the p-type side electrode side.

In particular, the nitrogen-containing region film is an ultrathin film.

Further, the nitrogen-containing region film is a delta-doped film of nitrogen.

The p-type semiconductor layer is made of ZnSe, Z
It is characterized by comprising nSSe, ZnSSeTe or MgZnSSe.

Further, the p-type semiconductor layer is formed on a GaAs substrate.

[0019]

BEST MODE FOR CARRYING OUT THE INVENTION A semiconductor laser according to an embodiment of the present invention will be described with reference to FIG. 1, which is a schematic sectional structural view.

In FIG. 1, reference numeral 1 is an n-type GaAs single crystal substrate. On this substrate 1, n-type ZnMgSSe having a layer thickness of 1 μm is formed.
Cladding layer 2, n-type ZnSSe optical guide layer 3 having a layer thickness of 0.1 μm, undoped ZnSe active layer 4, layer thickness of 0.1 μm
m p-type ZnSSe optical guide layer 5 and p having a layer thickness of 1 μm
The type ZnMgSSe cladding layer 6 is epitaxially grown in this order.

On the p-type cladding layer 6, a nitrogen-doped p-type ZnSe crystal film 7a having a layer thickness of 5 nm and an acceptor concentration of 1 × 10 ¹⁸ cm ⁻³ and an acceptor concentration of 1.2 × 1 are formed.
A laminated structure layer in which, for example, 10 pairs of p-type nitrogen delta-doped films 8 having a layer thickness of 0 ¹⁹ cm ^{−3 and} a thickness of approximately 2 Å are alternately grown, and a nitrogen-doped acceptor concentration at the top thereof is 1 × 10 ¹⁸ cm ^−. The p-type ZnSe crystal film 7b having a layer thickness tÅ of ³ is epitaxially grown, and the p-type ZnSe crystal films 7a and 7b form a so-called conventional p-type contact layer 7.

Reference numeral 9 denotes a p-type side electrode made of Au formed on the contact layer 7, and 10 denotes In formed on the lower surface of the substrate 1.
Is an n-type side electrode.

As described above, in this semiconductor device, p-type ZnS is used.
The e-contact layer 7 has a high-concentration nitrogen delta-doped film (high-concentration nitrogen-containing region film) 8 in the vicinity of the p-type side electrode 9 and a plurality of high-concentration nitrogen delta-doped films (high-concentration nitrogen-containing region film) spaced apart from each other by a predetermined distance. Including 8, 8, ...

A manufacturing process of such a semiconductor device will be briefly described. Incidentally, FIG. 2 is a schematic configuration diagram of an MBE (molecular beam epitaxy) apparatus used in this embodiment.

In FIG. 2, 11 is a vacuum container, 12 is an exhaust port connected to a vacuum pump (not shown) to evacuate the inside of the vacuum container 11, and 13 supports the substrate 1 installed in the vacuum container. It is a substrate holder for heating the substrate 1 and maintaining it at a desired crystal growth temperature. 14, 15, 16, 1
Reference numeral 7 denotes high-purity Zn (zinc), high-purity Se (selenium), high-purity S (sulfur), and high-purity for irradiating the surface of the substrate 1 installed in the vacuum container 11 with a molecular beam. Of Mg
A cell as a molecular beam source in which (magnesium) is stored, and 18 is a nitrogen for plasma doping method installed in a vacuum chamber 11 for irradiating the surface of the substrate 1 with a gas for p-type dopant simultaneously with the molecular beam. The cell 19 is a chlorine cell as a molecular beam source that stores high-purity ZnCl ₂ for irradiating the surface of the substrate 1 with the molecular beam for the n-type dopant at the same time as the molecular beam.

An example of a method of manufacturing the above semiconductor laser using this device will be described below. The only difference from the conventional method is the method of manufacturing the p-type contact layer 7 containing the delta-doped film 8. Therefore, only this point will be described in detail.

First, after mounting a GaAs semiconductor substrate as the substrate 1 on the substrate holder 13, the inside of the vacuum chamber 11 is evacuated to a high vacuum, preferably about 10 ^-9 Torr.

After that, the cells 14, 15, 16 are heated with the substrate 1 kept at a crystal growth temperature (substrate temperature) of 260.degree.
17 is heated, and a molecular beam made of Zn, a molecular beam made of Se, a molecular beam made of S, M
A molecular beam composed of g is appropriately emitted, and the nitrogen molecules are connected to a gas cylinder (not shown) containing nitrogen molecules (N ₂ ) as a p-type dopant, and the nitrogen molecules are supplied with high-frequency power of 140 W at high frequency power 140 W. A nitrogen plasma gas turned into plasma under the conditions is irradiated, and a molecular beam of Cl from the chlorine cell 19 is irradiated as the n-type dopant.

The p-type ZnSe crystal film 7a and the p-type ZnSe crystal film 7b of the p-type contact layer 7 are formed in the same manner as in the conventional case.
From each of the cells 14, 15 and 18 above, 1.2 × 10 ⁻⁷ To
It is formed by simultaneously irradiating a molecular beam of Zn of rr, a molecular beam of Se of 1.8 × 10 ⁻⁷ Torr, and a nitrogen plasma gas of 1 × 10 ⁻⁶ Torr. On the other hand, the nitrogen delta-doped film 8 is 1.2 × 10 ⁻⁷ To in order to suppress the evaporation of Zn while stopping the irradiation of the molecular beam made of Se.
Irradiation with a molecular beam of Zn of rr and 1 × 10
It is formed by irradiating a nitrogen plasma gas of ^-6 Torr.

The formation of the high-concentration nitrogen delta-doped film 8 in such a device can be confirmed by, for example, measuring the capacitance-voltage characteristics. As an example, FIG. 3 is a profile of the acceptor concentration of the nitrogen delta-doped film 8 formed by irradiating the Zn molecular beam and the nitrogen plasma gas for 10 minutes while stopping the supply of Se.

From FIG. 3, the acceptor concentration of the nitrogen delta-doped film 8 thus formed is 1.2 × 10 ¹⁹ cm.
^It can be seen that a high concentration of ^-3 can be formed. Moreover, since the above-mentioned profile approximates the pseudo-Gaussian distribution, it can be seen that the surface density of the nitrogen delta-doped film 8 is a high acceptor concentration of 6 × 10 ¹² cm ^-2 .

From this fact, the nitrogen dope has a large film thickness.
If the acceptor concentration is 1 × 10 ¹⁸cm^-3Greater than
However, it is difficult to achieve high
It turns out that the septa concentration can be used.

Thus, nitrogen doping can be made to have a high acceptor concentration by reducing the width of the doped region. By the way, in the above description, the nitrogen delta-doped film which is ideally composed of a monoatomic layer is shown as an example, but a high concentration nitrogen-containing region film which is an ultrathin film wider than this can also be used.

FIG. 4 shows the contact layer 7 of the semiconductor laser.
3 is a schematic band structure diagram of FIG.

As can be seen from FIG. 4, the valence band term in each high-concentration nitrogen delta-doped film 8 is located higher than the Fermi level at zero bias, and as a result, degenerate.

Due to this degeneracy, holes are localized in the high-concentration nitrogen delta-doped film 8 adjacent to the p-type side electrode 9,
Holes are supplied from the adjacent doped film 8 to the depletion layer side generated between the p-type side electrode 9 and the contact layer 7. Therefore, the width of the depletion layer can be reduced.

Moreover, when an electric field is applied (device operation) to this structure, the depletion layer generated between the p-type side electrode 9 and the contact layer 7 has a high resistance, so that the applied electric field is concentrated and this The energy band of the depletion layer bends extremely. As a result, the localized wave function of the holes in the high-concentration nitrogen delta-doped film 8 adjacent to the p-type side electrode 9 changes so as to exude to the p-type side electrode 9. As a result, the tunnel probability (tunnel current) of holes from the p-type side electrode 9 to the contact layer 7 side is increased by the application of the electric field, so that a good ohmic contact can be obtained.

In addition to the high-concentration nitrogen delta-doped film 8 adjacent to the p-type side electrode 9 and the plurality of high-concentration nitrogen delta-doped films 8 separated from each other by a predetermined distance, the wave function of holes of the adjacent films 8 is different. Since the predetermined distance (preferably 10 nm or less) is set so as to overlap, the device resistance becomes small. Moreover, it has an effect of reducing the width of the depletion layer.

FIG. 5 is a calculation result showing the relation between the layer thickness t of the p-type ZnSe crystal film 7b in contact with the p-type side electrode 9 and the characteristic contact resistance of the device.

From FIG. 5, the contact resistance is generally 10 ⁻⁴ Ω.
Since it is preferably about cm ² or less, the preferable film thickness of the p-type ZnSe crystal film 7b in contact depends on the material of the p-type side electrode 9 and the like, but is typically 26 Å or less.

Although the nitrogen plasma doping method is used in the above description, the nitrogen gas doping method can also be used.

Although the p-type ZnSe crystal contact layer has been described above, the Z-type contact layer such as the p-type MgZnSSe crystal contact layer or the p-type ZnSSeTe crystal contact layer is used.
The same can be applied to the p-type semiconductor crystal contact layer made of a II-VI group compound semiconductor containing n and Se as main components.

If the p-type contact layer has a p-type high-concentration nitrogen-containing region film at least in the vicinity of the p-type side electrode, good ohmic contact can be made. Therefore, it is not necessary to provide a plurality of high-concentration nitrogen-containing region films. Good.

In addition, although the semiconductor laser has been described in the above embodiment, the semiconductor laser can be appropriately used for other semiconductor devices such as a light emitting diode.

[0045]

The semiconductor device of the present invention has a p-type semiconductor layer made of a II-VI group compound semiconductor containing Zn and Se.
In the semiconductor device including the mold side electrode, the p-type semiconductor layer has a nitrogen-containing region film having an acceptor concentration higher than that of the p-type semiconductor layer in the vicinity of the p-type side electrode. This nitrogen-containing region film can be easily formed with a large acceptor concentration, and since it is not necessary to control this film thickness with high precision, it can be easily and reproducibly manufactured.

The valence band term in the nitrogen-containing region film having a high acceptor concentration is located higher than the Fermi level at 0 bias and can be degenerated.

Due to this degeneracy, holes are localized in the nitrogen-containing region film, so that holes are supplied from this nitrogen-containing region film to the depletion layer side generated between the p-type side electrode and the p-type semiconductor layer. . Therefore, the width of the depletion layer can be reduced.

Moreover, when an electric field is applied to this structure (device operation), the depletion layer generated between the p-type side electrode and the p-type semiconductor layer has a high resistance, so that the applied electric field is concentrated,
The energy band of the depletion layer is extremely bent, and the wave function of the localized hole in the nitrogen-containing region film is changed so as to exude to the p-type side electrode. As a result,
By applying an electric field, the tunnel probability (tunnel current) of holes from the p-type side electrode to the p-type semiconductor layer is increased, so that good ohmic contact can be obtained.

In such a structure, there is almost no difference in lattice constant between the p-type semiconductor layer and the nitrogen-containing region film.
Good lattice matching with an aAs semiconductor substrate or a ZnSe substrate is possible. As a result, the p-type semiconductor layer and the nitrogen-containing region film have good crystallinity.

Further, when the distance between the p-type side electrode and the nitrogen-containing region film is 26 Å or less, the contact resistance becomes a very preferable value.

Furthermore, when the nitrogen-containing region film is an ultra-thin film, nitrogen can be easily doped at a high concentration, so that the acceptor concentration can be easily increased. In particular, when the nitrogen-containing region film is a nitrogen delta-doped film, it can be doped at a higher concentration, so that the acceptor concentration can be easily increased.

When the p-type semiconductor layer has a nitrogen-containing region film having an acceptor concentration higher than that of the p-type semiconductor layer in addition to the vicinity of the p-type side electrode side, the plurality of nitrogen-containing region films are adjacent to each other. Since the predetermined distance can be set so that the wave functions of the holes of the region film overlap, the device resistance can be reduced.

[Brief description of drawings]

FIG. 1 is a schematic sectional structural view of a semiconductor laser according to an embodiment of the present invention.

FIG. 2 shows an MBE used for manufacturing the semiconductor laser.
It is a schematic structure figure showing an apparatus.

FIG. 3 is a diagram showing a profile of an acceptor concentration of a nitrogen delta-doped film.

FIG. 4 is a schematic band structure diagram of a contact layer portion of the semiconductor laser.

FIG. 5 is a diagram showing a relationship between a distance between a p-type side electrode and a high-concentration nitrogen-containing region film adjacent thereto and a characteristic contact resistance.

[Description of Reference Signs] 1 n-type GaAs substrate 7 p-type contact layer (p-type semiconductor layer) 7a p-type ZnSe layer 7b p-type ZnSe layer 8 p-type high-concentration nitrogen delta-doped film (high-concentration nitrogen-containing region film) 9 p-type Side electrode

Claims (7)

[Claims] 1. A semiconductor device having a p-type side electrode on a p-type semiconductor layer made of a II-VI group compound semiconductor containing Zn and Se, wherein the p-type semiconductor layer is near the p-type side electrode. And a nitrogen-containing region film having an acceptor concentration higher than that of the p-type semiconductor layer. 2. The semiconductor device according to claim 1, wherein the distance between the p-type side electrode and the nitrogen-containing region film is 26 Å or less. 3. The p-type semiconductor layer has a nitrogen-containing region film having an acceptor concentration higher than that of the p-type semiconductor layer, in addition to the vicinity of the p-type side electrode side. Semiconductor device. 4. The semiconductor device according to claim 1, wherein the nitrogen-containing region film is an ultrathin film. 5. The semiconductor device according to claim 4, wherein the nitrogen-containing region film is a nitrogen delta-doped film. 6. The p-type semiconductor layer is ZnSe or ZnS.
6. The semiconductor device according to claim 1, wherein the semiconductor device is made of Se, ZnSSeTe, or MgZnSSe. 7. The p-type semiconductor layer is formed on a GaAs substrate.
The semiconductor device according to 4, 5, or 6.