JPH06350199A - Semiconductor light emitting device and its manufacturing method - Google Patents

Abstract

PURPOSE:To improve the power consumption and temperature characteristics by causing the necessary current to flow at a low voltage between the p-type II-VI compound semiconductor film and the electrode. CONSTITUTION:After forming a ZnCdSSe type of II-VI semiconductor film 2 on an n-type GaAs substrate by the growing using MBE successively the n-type semiconductor layer 8, active layer 5, and p-type semiconductor layer 9 at a substrate temperature of 350 deg.C or less, a p-type AlGaAs film 10 with a carrier concentration of 10<19>/cm<3> or more and a p-type GaAs film 11 are grown using MBE successively on the p-type semiconductor layer 9 at a substrate temperature lower than the substrate temperature at which the II-VI compound semiconductor film 2 was grown, and finally the electrode 12 is formed on top of these layers. In this manner, the energy band gap is made to become successively higher from the electrode 12 to the II-VI compound semiconductor film 2, and the voltage-current characteristic is improved utilizing the fact that the current decreases exponentially with increasing height of the energy barrier.

Description

Detailed Description of the Invention

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a semiconductor laser device, a blue light emitting portion which is an element in a display panel of a display of various electronic devices, a blue light emitting element (LED) used alone in a display device, and other CDs. Player,
The present invention relates to a semiconductor light emitting device used as a signal reading and writing light emitting element in a LD player and a magneto-optical disk player, a light emitting element of a bar code reader, and the like, and a manufacturing method thereof.

[0002]

2. Description of the Related Art FIG. 5 schematically shows a basic structure of a semiconductor laser device as a semiconductor light emitting device of this type and a state of an energy band corresponding to the basic structure. Generally, in a semiconductor laser device, a semiconductor N-type layer B1, an active layer B2, and a semiconductor P-type layer B3 are sequentially formed on a surface of an N-type semiconductor substrate A by MB.
Semiconductor film B formed by E (Molecular Beam Epitaxy) growth
And a metal electrode E ₁ provided on the back surface of the substrate A.
When forward between the metal electrodes E2 provided on the surface of the semiconductor P-type layer B3 of the semiconductor film uppermost layer direction, i.e. by applying a bias voltage from the electrode E2 to electrode E _1, so that the light emitting from the active layer B ₂ It is configured.

As is well known, in the energy band structure of the semiconductor laser device having the above configuration, the energy levels of the semiconductor N-type layer B ₁ and the semiconductor P-type layer B ₃ are high, and the active layer C which is the PN junction has an energy level. A valley is formed, and an energy barrier Δ is provided between the electrodes E ₁ and E ₂ and the semiconductor film B.
V occurs.

Therefore, the voltage required for obtaining the current I enough for the hole h to exceed the energy barrier ΔV is set to the electrodes E2 and E1.
When applied during this period, the carriers thus injected, that is, holes h and electrons, are confined in the active layer C having a low energy level, and stimulated emission actively occurs. Then, when the excitation current exceeds the threshold value, light resonates between both parallel end faces of the active layer C, and laser oscillation occurs.

FIG. 6 shows an example of a more specific structure of a conventional semiconductor laser device. In the device shown in this figure, an N-type GaAs substrate 21 is used as an N-type semiconductor substrate, and a ZnCdSSe (or MgZnCdSSe) II-VI group semiconductor film 22 is formed as a semiconductor film on this substrate 21. , A so-called ZnSe-based blue light emitting semiconductor laser.

The II-VI semiconductor film 22 includes an N-type ZnSe layer 23 which is a buffer layer, an N-type ZnSSe layer 24 which is a cladding layer, a ZnCdSe layer 25 which is an active layer, and a P layer which is a cladding layer.
A type ZnSSe layer 26 and a P type ZnSe layer 27 which is a buffer layer are MBE grown on the substrate 21 in that order,
A positive electrode 28 is formed by vapor-depositing a metal such as Au directly on the P-type ZnSe layer 27 which is the uppermost layer of the II-VI semiconductor film.
Reference numeral 29 is a negative electrode formed on the back surface of the substrate 21.

[0007]

By the way, in the above-described semiconductor laser device having the conventional structure, the metal electrode 28 is formed directly on the P-type ZnSe layer 27. However, such a ZnSe-based P-type semiconductor is directly formed on the metal. It is known that Schottky type voltage / current characteristics exist between the two in the joined state.

That is, as is apparent from the energy band structure shown in FIG. 7, in the related art, when a forward bias voltage is applied between the electrodes 28 and 29, the P-type ZnSe forming the surface layer of the II-VI semiconductor film 22 is formed. Since a steep Schottky type energy barrier ΔV is generated between the layer 27 and the metal positive electrode 28, the current necessary for the holes h to exceed the energy barrier ΔV unless a considerably high voltage is applied. Can't get

Therefore, in the above-mentioned conventional structure, not only the power consumption required for driving the device increases, but also the device consumes several amperes.
Since a large current flows, the current density in the device becomes very high, and heat generation at a high temperature is inevitable during driving. As described above, in the above conventional device, there is a problem that power consumption increases and it is difficult to operate the device in a normal temperature environment due to thermal destruction.

In order to solve the above-mentioned problems, the structure is such that a current easily flows from the metal electrode 28 to the II-VI group semiconductor film 22, and the bias voltage applied between the electrodes 28 and 29 is made as low as possible. Although it is necessary to suppress the temperature, it is conceivable to maintain the II-VI group semiconductor film 22 at a temperature higher than the growth temperature after forming the electrode 28, for example.

That is, when the II-VI semiconductor film 22 is MBE-grown on the substrate 21, the substrate temperature is usually 350 ° C. or less. Therefore, the II-VI semiconductor film 2
After depositing the metal electrode 28 on the second layer 2, the semiconductor film 22 is again formed.
Is heated to a temperature higher than the growth temperature, for example, about 400 ° C. to diffuse the metal forming the electrode 28 into the II-VI semiconductor film 22.

When the metal is diffused into the P-type ZnSe layer 27 which is the surface layer of the II-VI semiconductor film as described above, the slope of the energy barrier ΔV is relaxed as shown by the broken line in FIG. Can be improved. However, II-
If the Group VI semiconductor film 22 is kept at a temperature higher than the growth temperature,
It has the property of increasing its own electric resistance.

Therefore, in this case, the alloying treatment performed by diffusing the electrode metal into the ZnSe layer 27 while suppressing the electric resistance of the P-type ZnSe layer 27 to a low level is difficult at present, and as a result, it is necessary. Electrode 28,
The same high voltage as in the above-described conventional example must be applied between the two terminals 29, which cannot be a solution to the above-mentioned problems.

As a solution different from the above, 10 ¹⁹
It is considered that the II-VI group semiconductor film 22 having a high carrier concentration of / cm ³ or more is grown on the substrate 21. In this way, as shown by the chain double-dashed line in FIG. 7, P-type ZnSe
Since the energy band of the layer 27 shifts so that the energy barrier becomes low, a structure in which current easily flows is obtained. II
In the case of group VI semiconductors, P having such a high carrier concentration is used.
Obtaining a mold film is technically almost impossible at present.

The present invention solves the above problems and improves the voltage / current characteristics between the II-VI group P-type film and the electrode so that the necessary current can flow at a low voltage. By doing so, it is intended to reduce the power consumption and the heat generation amount and improve the temperature characteristics of the entire semiconductor light emitting device.

[0016]

In order to achieve the above object, in a semiconductor light emitting device of the present invention, a semiconductor film in which a semiconductor N-type layer, an active layer, and a semiconductor P-type layer are laminated in this order is formed of GaAs. In a semiconductor light emitting device formed on a substrate, the semiconductor film is ZnCdSS obtained by MBE growing on the GaAs substrate.
e-type or MgZnCdSSe-based II-VI group semiconductor,
MB is formed on the uppermost semiconductor P-type layer of the II-VI semiconductor film.
It is assumed that a P-type AlGaAs film and a P-type GaAs film, which have been grown by E, are formed in this order in a laminated shape, and an electrode is further formed on the P-type GaAs film.

In the above structure, preferably P-type AlGaAs
Both the film and the P-type GaAs film have a carrier concentration of 10 ¹⁹ / cm ³ or more.

In the method for manufacturing a semiconductor light emitting device of the present invention, the semiconductor N-type layer, the active layer,
MBC-grown ZnCdSSe system or M in the order of semiconductor P-type layers
After a gZnCdSSe-based II-VI group semiconductor film is formed on a GaAs substrate, the semiconductor P as the uppermost layer of the II-VI group semiconductor film is formed at a substrate temperature lower than the substrate temperature during the growth of the II-VI group semiconductor film. A P-type AlGaAs film and a P-type GaAs film are sequentially formed on the mold layer in the order M.
BE growth is performed, and then an electrode is formed on the P-type GaAs film.

[0019]

The size of the energy band gap with respect to the electrode in each layer having the above-mentioned structure is determined by P-type GaAs film <P-type AlGaAs
Film <Semiconductor P-type layer made of II-VI semiconductor. Therefore, the state of the energy band from the electrode to the semiconductor P-type layer is in a state in which a level difference is created stepwise,
The energy barrier is divided into three stages.

Generally, the amount of current flowing through the PN junction structure between the positive and negative electrodes decreases exponentially with the height of the energy barrier. Therefore, as in the conventional configuration, the electrodes and the semiconductor P are
If there is a single large energy barrier between the mold layers, the current is more likely to flow when divided into three stages as described above, so even if the energy barriers have the same potential difference,
The voltage for obtaining the current required for holes to cross the energy barrier between the electrode and the semiconductor P-type layer can be greatly reduced as compared with the conventional case.

Further, according to the method of the present invention, P-type AlGaAs
It is possible to avoid alteration of II-VI group semiconductor film due to diffusion of AlGaAs and GaAs by setting the substrate temperature during growth of P-type GaAs film to below the substrate temperature during growth of II-VI group semiconductor film. become.

[0022]

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS An embodiment in which the present invention is applied to a semiconductor laser device will be described below with reference to the drawings. FIG. 1 schematically shows the configuration of this embodiment. The device shown in this figure is
This is a blue light emitting semiconductor laser in which a ZnCdSSe-based II-VI group semiconductor film 2 is formed on a type GaAs substrate 1.

The II-VI group semiconductor film 2 includes an N-type ZnSe layer 3 which is a buffer layer, an N-type ZnSSe layer 4 which is a clad layer, and ZnCdS.
An e-layer 5, a P-type ZnSSe layer 6 which is a clad layer, and a P-type ZnSe layer 7 which is a buffer layer are formed on the N-type GaAs substrate 1 in the order named M.
It was grown by BE, whereby a semiconductor N-type layer 8 composed of an N-type ZnSe layer 3 and an N-type ZnSSe layer 4 and a P-type ZnS layer were formed.
PN with the semiconductor P-type layer 9 composed of the Se layer 6 and the P-type ZnSe layer 7
PN with ZnCdSe layer 5 as an active layer sandwiched in the junction
It is configured as a junction element structure.

An MBE-grown P-type AlGaAs film 10 is formed on the P-type ZnSe layer 7 which is the uppermost layer of the II-VI group semiconductor film, and further MBE-grown on the P-type AlGaAs film 10 in the same manner. A P-type GaAs film 11 is formed, and the P-type Ga is formed on the P-type GaAs film 11.
A positive electrode 12 is formed on the As film 11 by depositing a metal such as Au. Reference numeral 13 denotes a negative electrode, which is formed on the back surface of the N-type GaAs substrate 1 by vapor-depositing a metal such as Au similar to that of the positive electrode 12.

In this embodiment, as shown in the plan view of FIG. 2, the positive electrode 12 is formed in a band shape with a constant width to prevent current diffusion and to contribute efficiently to the light emission. However, the shape of the positive electrode 12 is not necessarily limited to the band shape.

When a bias voltage is applied between the positive and negative electrodes 12 and 13 in the forward direction, that is, when a bias voltage is applied from the positive electrode 12 to the negative electrode 13 in the above structure, a current flows in the positive electrode 12 and the P-type GaAs film 11.
And through the P-type AlGaAs film 10 to the II-VI group semiconductor film 2 and the current causes the holes to pass through the energy barrier between the positive electrode 12 and the II-VI group semiconductor film 2 and the semiconductor P-type layer. 9
Flow into the ZnCdSe layer 5, which is an active layer, and similarly electrons flow from the semiconductor N-type layer 8 into the ZnCdSe layer 5.

By injecting carriers in this way, electrons and holes confined in the ZnCdSe layer 5 having a low energy level are recombined, and natural light is emitted from the ZnCdSe layer 5. Furthermore, when the excitation current exceeds the threshold,
Transition from natural light emission to stimulated emission occurs, and light resonates between both parallel end faces of the ZnCdSe layer 5, causing laser oscillation.

FIG. 3 shows the state of the energy band in this embodiment. As shown in this figure, the size of the energy band gap with respect to the positive electrode 12 of each layer is
The P-type GaAs film 11 <P-type AlGaAs film 10 <the P-type ZnSe layer 7 of the II-VI group semiconductor film 2 increases in this order. Therefore, the energy barrier between the positive electrode 12 and the P-type ZnSe layer 7 is 3
It becomes a step-like step, and the potential difference between each is the positive electrode 12
ΔV ₁ between the P-type GaAs film 11 and the P-type GaAs film 11, and the P-type GaAs film 11 and the P-type Al
The space between the GaAs films 10 is ΔV ₂ , and the space between the P-type AlGaAs film 10 and the P-type ZnSe layer 7 is ΔV ₃ .

The sum of these ΔV _{1 to} ΔV ₃ is shown in FIG.
Although the potential difference ΔV between the positive electrode 28 and the P-type ZnSe layer 27 of the conventional configuration shown in FIG.
The amount of current flowing through the PN junction structure between the three decreases exponentially with the height of the energy barrier.

FIG. 4 shows the voltage / current characteristics of this embodiment and the conventional example. As is clear from this figure, in this embodiment, compared with the conventional example, even if the energy barrier of the same potential difference, the holes h exceed the energy barrier between the positive electrode 12 and the P-type ZnSe layer 7. It is possible to greatly reduce the voltage for obtaining the required current.

Next, the manufacturing process of the semiconductor laser device having the above structure will be described. First, a ZnCdSSe group II-VI group semiconductor is formed on an N-type GaAs substrate 1 whose substrate temperature is set to a predetermined temperature value of 350 ° C. or less. By MBE growing the film 2,
N-type ZnSe layer 3, N-type ZnSSe layer 4, Z on the N-type GaAs substrate 1.
The nCdSe layer 5, the P-type ZnSSe layer 6 and the P-type ZnSe layer 7 are formed in a laminated shape.

Then, the substrate temperature is set lower than the substrate temperature during the growth of the II-VI group semiconductor film 2, that is, lower than 350 ° C., for example, about 300 ° C., and under this temperature condition, the II-VI group is formed. A P-type AlGaAs film 10 is MBE grown on the P-type ZnSe layer 7 which is the uppermost layer of the semiconductor film 2. In this case, the carrier concentration of the P-type AlGaAs film 10 is 10 ¹⁹ / cm ³ or more.

Further, the P-type GaAs film 11 is MBE-grown on the P-type AlGaAs film 10. In this case, the P-type GaAs film 11
Is less than the critical thickness, and the carrier concentration is P
Similar to the type AlGaAs film 10, it is 10 ¹⁹ / cm ³ or more. Further, the substrate temperature at this time is also set to be equal to or lower than the substrate temperature at the time of growing the II-VI group semiconductor film 2 as in the case of growing the P-type AlGaAs film 10.

As described above, the P-type AlGaAs film 10 and the P-type GaAs
By setting the growth temperature of the film 11 to be equal to or lower than the growth temperature of the ZnCdSSe-based II-VI group semiconductor film 2, the P-type ZnSe layer 7
It is possible to prevent the AlGaAs film 10 and the P-type GaAs film 11 from being diffused to form an alloy layer having a high electrical resistance, and to prevent the P-type ZnSe layer 7 from being altered.

After the P-type GaAs film 11 is formed on the P-type AlGaAs film 10, Au serving as the positive electrode 12 is formed on the P-type GaAs film 11.
And other metals are vapor-deposited, and the positive electrode 12 and the P-type GaAs film 11 are further deposited.
And unnecessary portions of the P-type AlGaAs film 10 are removed by a method such as etching, and finally, as shown in FIG.
The AlGaAs film 10, the P-type GaAs film 11 and the positive electrode 12 are formed into a strip shape.

In the above embodiment, the semiconductor film 2 is made of ZnCd.
Although shown as being composed of an SSe-based II-VI group semiconductor, in the present invention, the semiconductor film 2 is formed of MgZnCdSSe-based II-VI.
Even if it is made of a group semiconductor, the same action and effect can be obtained.

[0037]

As described above, according to the semiconductor light emitting device of the present invention, ZnCdSS grown by MBE on a GaAs substrate is grown.
MBE is formed on the e-based or MgZnCdSSe-based II-VI group semiconductor film.
When the bias voltage is applied between the positive and negative electrodes, the grown P-type AlGaAs film and the P-type GaAs film are laminated in that order and electrodes are further formed on the P-type GaAs film. A sharp energy barrier does not occur between the electrode and the semiconductor P-type layer, but an energy barrier divided in stages is generated due to the existence of the P-type AlGaAs film and the P-type GaAs film.

In this case, the amount of current flowing through the PN junction structure between the positive and negative electrodes exponentially decreases with respect to the height of the energy barrier, so that the current easily flows. Therefore, even if the energy barriers have the same potential difference, the voltage for obtaining the current required for holes to cross the energy barrier between the electrode and the semiconductor P-type layer can be greatly reduced as compared with the conventional case. it can.

As described above, in the present invention, the voltage / current characteristic between the II-VI group P-type film and the electrode is improved so that the required current flows at a small voltage, so that the current required for the operation of the device is improved. The voltage for obtaining the voltage is reduced, and the power consumption is reduced. Moreover, since the amount of heat generated is reduced by suppressing the voltage low, it is possible to improve the temperature characteristics of the semiconductor light emitting device as a whole, and it is also possible to suppress the deterioration rate of the device and prolong the product life. It has become effective.

According to the second aspect, the P-type AlGaAs film and the P-type GaAs film having a carrier concentration of 10 ¹⁹ / cm ³ or more are used, so that the II-VI having such a high carrier concentration is obtained.
In the present situation where it is impossible to obtain a group P-type film, a structure in which a current easily flows can be formed in combination with the effect of improving the voltage / current characteristics.

According to the third aspect, the MBE growth of the II-VI semiconductor film on the GaAs substrate is performed at a substrate temperature of 350 ° C. or lower, and the II-VI semiconductor film is grown. At a substrate temperature below the substrate temperature,
A P-type AlGa layer is formed on the uppermost semiconductor P-type layer of the II-VI group semiconductor film.
Since the As film and the P-type GaAs film are grown by MBE, it is possible to prevent the P-type AlGaAs film and the P-type GaAs film from being diffused to form an electrically high resistance alloy layer. It is possible to avoid alteration of the group VI semiconductor film.

[Brief description of drawings]

FIG. 1 is a sectional view schematically showing the configuration of an embodiment of the present invention.

FIG. 2 is a plan view thereof.

FIG. 3 is a characteristic diagram showing a state of an energy band in the present embodiment.

FIG. 4 is a diagram showing voltage / current characteristics of the present example and a conventional example in comparison.

FIG. 5 is a diagram schematically showing a configuration of a general semiconductor laser and a state of an energy band corresponding to the configuration.

FIG. 6 is a sectional view schematically showing the configuration of a conventional example.

FIG. 7 is a characteristic diagram showing an energy band in a conventional example.

[Explanation of symbols]

 1 GaAs Substrate 2 II-VI Group Semiconductor Film 5 Active Layer 8 Semiconductor N-type Layer 9 Semiconductor P-type Layer 10 P-type AlGaAs Film 11 P-type GaAs Film 12 Electrode

Claims (3)

[Claims] 1. A semiconductor light emitting device having a semiconductor film, in which a semiconductor N-type layer, an active layer, and a semiconductor P-type layer are stacked in this order on a GaAs substrate, wherein the semiconductor film is
ZnCdSSe system or MgZnCdSSe grown by MBE on GaAs substrate
P formed by MBE growth on the uppermost semiconductor P-type layer of the II-VI semiconductor film of the II-VI group semiconductor film.
A semiconductor light emitting device, characterized in that a p-type AlGaAs film and a p-type GaAs film are laminated in this order, and electrodes are further formed on the p-type GaAs film. 2. The semiconductor light emitting device according to claim 1, wherein both the P-type AlGaAs film and the P-type GaAs film have a carrier concentration of 10 ¹⁹ / cm ³ or more. 3. A semiconductor N-type layer at a substrate temperature of 350 ° C. or lower,
MBC grown ZnCdSSe in order of active layer and semiconductor P-type layer
System or MgZnCdSSe system II-VI group semiconductor film is formed on a GaAs substrate, under the substrate temperature below the substrate temperature during the growth of the II-VI group semiconductor film, the II-VI group semiconductor film top layer A method of manufacturing a semiconductor light emitting device, comprising: forming a P-type AlGaAs film and a P-type GaAs film on a semiconductor P-type layer by MBE in that order, and further forming an electrode on the P-type GaAs film.