JP2783140B2 - Surface treatment method for compound semiconductor device - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for reducing reactive current due to non-radiative recombination occurring on the surface of a compound semiconductor device such as an etched surface.

[0002]

2. Description of the Related Art In a compound semiconductor device manufactured by processing by a method such as etching, a reactive current due to non-radiative recombination generated on a processed surface of the device is expressed by:
It is considered as one factor of deterioration of device characteristics. Since the surface effect becomes more important as the element size becomes smaller,
The effect of surface non-radiative recombination is more serious for devices with smaller processing sizes. In particular, quantum wire devices and quantum dot devices, which have been actively studied in recent years, necessarily have an extremely small element size. Therefore, reduction of surface non-radiative recombination is an important issue for realizing practical devices.

Conventional methods for reducing non-radiative recombination of the processed surface of these devices include the following: a. Embedding the device with a high band gap material to prevent carriers from diffusing near the surface (embedding regrowth method: Applied Physics Letter (Appli)
Physics Letter), Vol. 63, 13
P. 07 (1993)), b. A method of inactivating the surface by covering the device surface with a high band gap material (surface passivation method:
JP-A-5-175602 (Japanese Patent Application No. 3-35574)
No. 5) "Method of manufacturing surface emitting laser"), c. A method of increasing the bandgap of the device surface by locally changing the composition of the material near the surface (intermixing method: Applied Physic Letter (A
Applied Physics Letter), 5th
9, pp. 1488 (1991); Applied Physic Letter (Applied Physi).
cs Letter), vol. 61, p. 2205 (1
992)) d. A method of treating the element surface with a sulfur compound and sulfurizing it (sulfur passivation method: applied physics, vol. 58, 13)
40 pages (1989)).

[0004]

Among the techniques described above, a to c agree with each other in that a high bandgap material is formed on the surface of the manufactured semiconductor device, but there are differences in the method of realizing the same. . The method a or b is a method in which another material having a high band gap is crystal-grown or deposited on the surface of the manufactured device. This method has the advantage that the range of choice of high bandgap material used for embedding and coating is wide, but it is difficult to maintain the crystallinity and coating properties of the interface,
Further, there is a disadvantage that the process of manufacturing the element is complicated. c
Is a method for modifying the element surface itself, and the steps required for the surface modification are simpler than the former, but a very large band gap of the surface layer obtained by the modification cannot be obtained. Although the method described in d is reported to have a great effect by a simple step, it is pointed out that there is a change with time, and the required sulfur compound usually grows a III-V compound semiconductor. Since the material system is different from the material system used for this purpose, it may be a source of contamination in the growth processing apparatus. The surface treatment method for a compound semiconductor device according to the present invention belongs to the category c in which the effect of reducing surface non-radiative recombination can be obtained by a relatively simple process. Even in the case of the method belonging to the category c, in the conventional method, the vicinity of the surface is made amorphous by ion beam implantation or the like for surface modification,
_It requires a process that requires expensive equipment separately, such as forming a dielectric coating layer such as _{2 on the} surface of the semiconductor. For this process, the device is carried out of a high vacuum chamber for growing and processing the device. Since the necessity arises, there is a concern that the device processing surface may be contaminated by exposure to the air, such as oxidation and carbide adhesion. Therefore, in order to produce a large number of practical devices at low cost, it was necessary to further simplify the surface treatment step and to perform the step in a vacuum chamber for performing growth processing.

It is an object of the present invention to provide a method for effectively treating a reactive current caused by non-radiative recombination of a surface without the risk of contamination by impurities.

[0006]

According to the present invention, there is provided a method for processing a surface of a compound semiconductor device, comprising the steps of: preparing a multilayer structure having a group III-V compound semiconductor containing gallium (Ga) and arsenic (As); Etching process
After that , heat treatment is performed in a phosphorus (P) atmosphere.

[0007]

Next, the basic operation of the present invention will be described.

[0008] Recent studies have shown that gallium arsenide (Ga
When a so-called group III-V compound semiconductor containing gallium (Ga) and arsenic (As) such as As) and indium gallium arsenide (InGaAs) is exposed to a phosphorus (P) atmosphere, phosphorus atoms enter the semiconductor from the semiconductor surface. However, the phenomenon of dissolving into the inside (solid solution) while replacing arsenic atoms was discovered. For example, Applied Physics Le
ter), Vol. 49, p. 1302 (1986), reports that surface morphology is degraded when P is irradiated to the InGaAs surface. This is InGa
InGaAs with large P composition due to substitution of As and P in As
This is because P is formed on the surface. On the other hand, P
In the case of irradiation, it is also found that GaAsP having a large P composition is formed on the surface by replacement of As and P in GaAs by the Journal of Electronic Materials (Journal of Electronic Materials).
terails) Vol. 21, p. 129 (1991)
Has been reported to. Also, the Applied Physics Letter
r) Vol. 63, p. 1047 (1993) proves that these results arise from the difference in the chemical bonding strength of arsenic and phosphorus atoms to gallium atoms. The principle of the present invention is based on this finding.

Generally, in a group III-V compound semiconductor containing arsenic such as gallium arsenide or indium gallium arsenide, a material in which arsenic atoms are replaced with phosphorus atoms has a higher band gap than the original material. For example, the band gap energy of gallium arsenide (GaAs) is 1.424 eV at room temperature, whereas that of gallium phosphide (GaP) is 2.78 eV. The band gap energy of indium arsenide (InAs) is 0.354 eV at room temperature, while that of indium phosphide (InP) is 1.344.
eV. When some of the arsenic atoms are replaced with phosphorus atoms, the band gap change as described above cannot be obtained, but there is no difference that the band gap becomes higher than before the replacement. Therefore, when the phosphorus solid solution phenomenon described above occurs, the band gap of the material near the surface of the compound semiconductor becomes large. Carriers cannot be diffused near the semiconductor surface due to the potential barrier resulting from the increase in the band gap, so the chance of non-radiative recombination at the surface is reduced, and consequently the reactive current is reduced.

Therefore, if this phenomenon is actively used,
It can be used as a surface treatment method for reducing reactive current due to surface non-radiative recombination. Phosphorus is common as a raw material of III-V compound semiconductors, and there is little concern about contamination such as sulfide.

[0011]

Embodiments of the present invention will be described below in detail. The following is an example showing that device characteristics were improved by fabricating a minute surface emitting semiconductor laser having an InGaAs active layer by dry etching and subjecting the etched surface to surface treatment by the method of the present invention. It is an example.

FIGS. 1 to 3 are sectional views showing a semiconductor layer structure formed in a step of manufacturing a surface emitting laser in one embodiment of the present invention.

An n-type AlAs layer 2 on an n-type GaAs substrate 1
The n-type GaAs layer 3 is formed with a thickness of λ / 4n _r (λ: laser oscillation wavelength substantially determined by the band gap of the active layer, n _r : refractive index of each semiconductor layer). Thereafter, the above steps are repeated, and the n-type lower semiconductor multilayer reflective film 4 is formed by laminating about 20 cycles.

Next, an n-type Al _x Ga _{1 -x} As (x =
0.3-0.7) about 500 angstroms to 1 micron
m. On the lower cladding layer 5, as an active layer 6, for example, In _y Ga having a thickness of about 100 Å is used.
_A quantum well structure including a _1-y As (y = 0.05 to 0.5) quantum well layer and a GaAs confinement layer having a thickness of about 30 to 200 angstroms is formed. This quantum well active layer 6
P-type Al _z Ga _{1 -z} As as the upper cladding layer 7
A (z = 0.3-0.7) layer is formed in a thickness of about 500 Å to 1 μm. On this upper cladding layer 7, a p-type A
Each formed by the thickness lambda / 4n _r a lAs layer 8 and the p-type GaAs layer 9, an upper semiconductor multilayer reflection film 10 of p-type by laminating about 10 to 20 cycles repeat the above steps. The steps so far are performed using crystal growth such as molecular beam epitaxy (MBE).

Next, an insulating film such as SiO ₂ or SiN is formed on the grown substrate at a thickness of about 1000 Å to 5000 Å, and a circular mask 11 is formed by photolithography. Using this mask 11, Cl
₂ Reactive ion beam etching (RI
By a dry etching technique such as a BE) method or an ion beam assisted etching (IBAE) method using Ar ions and Cl ₂ gas, etching is performed right under the active layer 6 to form a columnar light emitting region 12 (FIG. 1). ). In this type of surface-emitting type semiconductor laser, carrier confinement and light confinement in the active layer are effectively performed by performing etching right below the active layer 6. When the active layer itself is etched as in this example, if the surface is exposed to the atmosphere without processing the processed surface, large surface non-radiative recombination occurs due to oxidation of the semiconductor surface and adhesion of carbides. Therefore, some processing surface treatment is required before exposure to the atmosphere. The present invention is particularly effective in such a case.

After the etching process, the sample is introduced into the high vacuum growth chamber by moving the sample in the high vacuum transfer path. At this time, since the sample is not exposed to the atmosphere, it is not subject to contamination such as oxidation and adhesion of carbide. Also, residual reactive gas (eg, chlorine molecules) and reaction products (eg, GaCl _x ) attached to the sample after etching can be easily removed by heating in a high vacuum transfer path, so that a clean semiconductor surface can be obtained. can get. By irradiating the sample with phosphorus gas (P2) for several minutes while heating the sample to about 400 ° C. in a high vacuum growth chamber, a surface protective semiconductor layer 13 composed of a layer in which As atoms in the sample are replaced with P atoms is formed. . At this time, the thickness of the formed surface protection semiconductor layer 13 is estimated to be about several tens angstroms to several hundred angstroms (FIG. 2).

Thereafter, the sample is taken out of the growth chamber, and the mask 11 is removed by etching with, for example, buffered hydrofluoric acid. Further, an Au / Cr layer is deposited as a p-side electrode 14 on the entire surface. Finally, AuGeNi / A is formed as an n-type electrode 15 on a portion other than the light emitting region 12 serving as a laser emitting portion on the back surface of the substrate.
A device is completed by depositing a uNi layer (FIG. 3).

In order to examine the effect of the present invention, the oscillation threshold currents of the device A to which the method according to the present invention is applied and the device B to which the method is not applied are compared. According to the results, the device of A has an oscillation threshold current of about 1 under the same conditions as the device of B
It was found to be reduced by a factor of 0. In addition, according to the results of another time-resolved fluorescence lifetime measurement experiment, it was found that the non-radiative recombination lifetime of the carriers in the device A was three times as long as that in the device B. These results show that non-radiative recombination on the etched side surface is equivalently suppressed in the A element to which the method of the present invention is applied, and the effectiveness of the method of the present invention has been proved.

In the above embodiment, the active layer has a single quantum well structure, and the material is InGaAs / GaAs. However, the present invention is not limited to this. Even if a multiple quantum well structure or a bulk material is used, other gallium and arsenic may be used. The present invention can also be applied to a material system that includes, for example, a GaAs / AlGaAs system.

In the above embodiment, an example in which the method of the present invention is applied to a semiconductor laser device has been described. However, the method of the present invention may be applied to other devices involving etching, such as a high electron mobility transistor (HEMT) and a heterogeneous device. The present invention is also applicable to a bipolar transistor (HBT) and the like.

[0021]

As described above, according to the surface treatment method for a compound semiconductor device of the present invention, the reactive current due to surface non-radiative recombination can be effectively reduced by a simple process, and a highly efficient compound can be obtained. Semiconductor devices can be mass-produced at low cost.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view showing a semiconductor laminated structure manufactured in a process according to an embodiment of the present invention.

FIG. 2 is a cross-sectional view showing a semiconductor laminated structure manufactured in a process in one embodiment.

FIG. 3 is a cross-sectional view showing a semiconductor laminated structure manufactured in a process in one embodiment.

DESCRIPTION OF SYMBOLS 1 n-type GAAs substrate 2 n-type AlAs layer 3 n-type GalAs layer 4 lower semiconductor multilayer reflection film n 5 lower cladding layer 6 active layer 7 upper cladding layer 8 AlAs layer 9 GaAs layer 10 semiconductor multilayer reflection film 11 Mask 12 light emitting region 13 surface protection semiconductor layer 14 p-type electrode 15 n-type electrode

Claims (1)

(57) [Claims] 1. A multi-layer structure having a group III-V compound semiconductor containing gallium (Ga) and arsenic (As) is etched.
A method for processing a processed surface of a compound semiconductor device, comprising: performing heat treatment in a phosphorus (P) atmosphere after performing a chining process.