KR940007450B1 - Manufacturing method of optical logic device - Google Patents

Abstract

The method is for manufacturing an optical logic device by applying electric field to a lattice of a multiple quantum well structure so that superior optical modulation characteristic is obtained. The method comprises the steps of: (A) growing a reflection layer (2) and an active region (3) by using MBE process; (B) forming an optical window and forming N-type doping region (4) and a P-type doping region (5) by injecting N-type ion and P-type ion perpendicalar to an active region (3); (C) forming an insulating area (6) to seperate devices electrically; (D) forming contact (7) on a N-type doping region (4) and a P-type region (5); and (G) spraying non-reflecting material on a layer (8).

Description

Method for manufacturing a horizontal field semiconductor optical switching device by ion implantation

1 shows a conventional semiconductor multi-quantum well optical switching device using a vertical electric field, a is a schematic diagram of a self electroopic effect device (SEED), and b is a symmetric-sEED (S-SEED) in which two SEEDs are connected in series. Schematic.

2 shows a semiconductor multiple quantum well optical switching device of the present invention using a horizontal electric field, wherein a is a schematic diagram of SEED, and b is a schematic diagram of S-SEED.

3 to 7 are cross-sectional views showing the manufacturing process of the SEED using a horizontal electric field according to the present invention.

8 is a cross-sectional view of the S-SEED completed by the present invention.

* Explanation of symbols for main parts of the drawings

1: undoped semi-insulated GaAs substrate or Cr doped GaAs substrate

2: light reflection layer 3: active area

4: N type doping area 5: P type doping area

6: electrically isolated region 7: electrode contact

8: antireflection film

The present invention provides a lattice layer in a multi-quantum well (MQW) structure in which thin lattice layers of GaAs having a small energy band gap and AlGaAs having a large energy band gap are alternately stacked by a crystal growth method. The present invention relates to a method for fabricating an optical logic device having a PIN structure that can obtain excellent optical modulation characteristics by applying an electric field in a horizontal direction. Particularly, ion implantation is applied to both walls of a multi-quantum well (MQW) lattice layer. The present invention relates to a method for manufacturing a horizontal field semiconductor optical switching device by simply forming doped regions of P type and N type using only an ion implantation method.

In a multi-quantum well (MQW) structure in which GaAs and AlGaAs lattice layers are alternately stacked, when the input light having energy close to the energy bandgap of GaAs is incident, strong exciton absorption peaks are generated in the quantum wells of GaAs. In this case, when an external electric field is applied in a direction perpendicular to the lattice layer, the excitation absorbing peak moves to a low energy band (Quantum Confined Stark Effect). By using this phenomenon, an optical logic device such as an optical intensity modulation device or an optical switching device can be manufactured.

In manufacturing such an optical logic device, conventionally, P-types are formed on the upper and lower portions of the multi-quantum wells in the process of growing crystals of the multi-quantum wells (MQW) in order to form an electric field in a direction perpendicular to the multi-quantum well region. And an N-type doping layer are grown (see FIG. 1).

Optical logic devices manufactured in this way have received a lot of attention due to their variety of functions. However, the devices manufactured by the above-described conventional method have a disadvantage in that a relatively strong external electric field (typically a supply voltage of 10 V or more) must be applied to sufficiently obtain the excitation absorption peak shift.

In addition, the switching speed is slow due to the time that the electric field is sequentially transmitted inside the multiple quantum well (MQW) layer formed of many quantum wells and the quantum barrier and the long lifetime of the excitons confined in the quantum well. there was.

SUMMARY OF THE INVENTION An object of the present invention is to provide a method for manufacturing a horizontal field semiconductor optical switching device which can operate at a low supply voltage, has a very fast switching speed, and has a simple manufacturing method.

In order to achieve the above object, the method of the present invention comprises the steps of sequentially growing an optical reflector stack and an active layer on an undoped semi-insulated GaAs substrate or a Cr doped GaAs substrate, And an N-type and a P-type by injecting impurities in a direction perpendicular to the active region to form an optical window to determine the path of output light and to form a horizontal electric field in the active region. Forming doped regions, electrically isolating respective elements, forming electrode contacts with a metal film on the N-type and P-type doped regions, and surface reflection of the optical window Coating an anti-reflecting (AR) film to reduce reflection loss caused by the coating.

Meanwhile, the present invention provides a method of simply manufacturing the S-SEED using the SEED obtained by performing each of the above-described steps. The SEEDs are connected in series, but the P-type doping region of one SEED and the N-type doping region of another SEED are connected to each other, and then a metal film is deposited. Hereinafter, the present invention will be described in detail with reference to the accompanying drawings.

2 shows a horizontal field semiconductor optical switching device according to the present invention, where a is a schematic diagram of SEED and b is a S-SEED.

In the present invention, a high energy ion implantation method is used to apply a uniform electric field in a horizontal direction to the multiple quantum well (MQW) region.

3 to 7 show the manufacturing process of the horizontal electric field feed according to the present invention. Hereinafter, the SEED manufacturing method of the present invention will be described in detail with reference to the accompanying drawings.

[Step 1]

A step of sequentially forming a light reflection layer and an active region on the substrate (FIG. 3); The light reflection layer 2 and the active region 3 are sequentially grown on the undoped semi-insulated or Cr-doped GaAs substrate 1 using an electron beam crystal growth (MBE: Molecular Beam Epitaxy) method. At this time, the active region 3 has an undoped GaAs / AlGaAs multi-quantum well structure as in the conventional vertical field type optical switching device (see FIG. 1). In addition, the width of the GaAs quantum wells should be small so that the excitons can be sufficiently confined in the quantum wells and the number of GaAs / AlGaAs pairs should be large enough to absorb the excitons as the incident light passes.

On the other hand, the light reflection layer 2 is made of a stack of dozens of GaAs and AlGaAs having a thickness corresponding to the incident light wavelength 1/4 so that the incident light is completely reflected. Incident light is incident on the surface of the active region 3 in a direction perpendicular to the surface.

Second Process

Forming an optical window for passage of incident light and output light and a doped region for a horizontal electric field in the active region (FIG. 4); 4 shows impurities of N-type and P-type ions in a direction perpendicular to the active region 3 to form an optical window for determining the path of incident light and output light and to form a horizontal electric field in the active region 3, respectively. Ion implantation is performed using an ion acceleration implanter or the like to form the N-type doped region 4 and the P-type doped region 5.

At this time, Si ions are implanted into the N-type doped region 4 as impurities, and Be ions are implanted into the P-type doped region 5.

Acceleration energy required in the ion implantation process varies depending on the mass of each implanted ion. That is, since the mass of Be ions is relatively light, the acceleration energy of the ion implanter is about 100 to 300 KeV in order to inject ions into the thick active region 3 of about 0.7 to 1 μm, whereas the mass of Si ions is Since it is relatively heavy relative to the mass of ions, the acceleration energy of the ion implanter is about 0.5 to 1.5 MeV.

[Third process]

Forming an electrically isolated region for electrically separating the elements SEED (FIG. 5); 5 shows a process of forming an electrical isolation region 6 for electrically separating each element by a proton bombardment method. Protons can easily penetrate because they are very light in mass, so that they can sufficiently isolate the active area of about 1 μm thick by appropriately adjusting the acceleration energy.

On the other hand, the formation of the electrically isolated region (6) by the proton impact method should be performed after the heat treatment of the ion implanted N-type doped region (4) and P-type doped region (5).

[4th process]

Forming electrode contacts on the doped regions (FIG. 6); As shown in FIG. 6, an electrode contact 7 is formed on the N-type doped region 4 and the P-type doped region 5 with a metal film. At this time, the metal used is Au, the electrode is formed by a non-alloyed ohmic contact method without heat treatment.

[5th process]

Anti-reflective (AR) film coating process (FIG. 7); An antireflection film 8 is applied to reduce the reflection loss caused by the surface reflection of the optical window. Therefore, the input light P _in and the output light P _out are input and output through the window of the deposited metal film, but the antireflection film 8 reduces the reflection loss caused by the window surface.

8 illustrates a process of manufacturing S-SEED by using the SEED completed by the first to fourth processes described above.

In the fourth process, two SEEDs are connected in series so that the N-type doped region 4 of one SEED and the P-type doped region 5 of the other SEED are adjacent to each other, and then a metal film is deposited. The S-SEED can be manufactured simply by performing the fifth process.

As described above, the method of the present invention has the following advantages.

First, in a multi-quantum well structure constructed by alternately stacking GaAs and AlGaAs, when an electric field is applied in a horizontal direction to each stacking surface, the remaining time of the excitons excited by the conduction band becomes very short, and a switching speed of several tens of picoseconds or less is achieved. It is possible to manufacture a high speed optical switching device having a.

Second, by forming an electric field in the stacking plane in the horizontal direction, the absorption peak of the excitons is rapidly decreased and the absorption curve is very gentle due to the rapid field ionization of the excitons in the GaAs quantum well. As a result, it is possible to operate the optical switching element at a low supply voltage.

Third, in the ion implantation doping method used to form the electric field in the horizontal direction, since the vertical section of the ion implantation region (4, 5 in FIG. 4) is much more linear than the impurity diffusion method, a uniform electric field can be formed in the entire active region. have.

Fourth, by using the ion implantation method to form the doped regions, the doped regions can be formed more easily and simply when forming the doped regions using the crystal growth method as in the conventional method.

Fifth, since the device can be optically and electrically isolated only by the ion implantation method and the doped regions are exposed on the surface of the device, the device can be easily manufactured without using a dry or chemical etching method.

Claims (11)

A first step of sequentially growing the light reflection layer 2 and the active region 3 on the GaAs substrate 1 by an electron beam crystal growth (MBE) method, and forming an optical window to determine a path of the incident light and the emitted light; In order to form a horizontal electric field in the active region 3, N-type and P-type ions are implanted in a direction perpendicular to the active region 3 to form an N-type doping region 4 and a P-type doping region 5, respectively. ), A third process of forming an electrically isolated region (6) in the active region (3) to electrically separate the elements, the N-type doped region (4) and the P-type A fourth process of forming an electrode contact 7 with a metal film on the doped region 5 and a fifth process of applying the antireflective film 8 to reduce reflection loss caused by surface reflection of the optical window. Horizontal field semiconductor optical switching, characterized in that How it's manufacturing. 2. The ion implantation acceleration energy of the N-type ions and the P-type ions respectively injected into the N-type doped region 4 and the P-type doped region 5 is characterized in that A method of manufacturing a horizontal field semiconductor optical switching element, characterized in that the mass and the P-type ions are changed correspondingly. 3. The method of claim 2, wherein the N-type ions are Be ions and the P-type ions are Si ions. The method according to claim 2 or 3, wherein the preferable ion implantation acceleration energy of the Be ions is 200 Kev, and the preferred ion implantation acceleration energy of the Si ions is 1 MeV. A method according to claim 1, wherein the electrically isolated region (6) is formed by a proton bombardment method. The light reflection layer 2 and the active region 3 are sequentially grown on the GaAs substrate 1 by the electron beam crystal growth (MBE) method, and an optical window is formed to determine the path of the input light and the output light. In order to form a horizontal electric field in the region 3, N-type and P-type ions are implanted in a direction perpendicular to the active region 3 to form the N-type doped region 4 and the P-type doped region 5, respectively. Forming, forming an electrically isolated region (6) in each of said active regions (3) and manufacturing a SEED; After the two SEEDs are connected in series so that the N-type doped region 4 of one SEED and the P-type doped region 5 of the other SEED manufactured in the step are adjacent to each other, a metal film is deposited to form an electrode contact ( 7) forming a S-SEED by forming an anti-reflective film (8) to reduce the reflection loss caused by the surface reflection of the optical window of the horizontal field semiconductor optical switching device Manufacturing method. 7. The ion implantation acceleration energy of the N-type ions and the P-type ions respectively injected into the N-type doped region 4 and the P-type doped region 5 is characterized in that the mass of the N-type ion and the A horizontal field semiconductor optical switching element, characterized in that it is changed corresponding to the mass of P-type ions. 8. The method of claim 7, wherein the N-type ions are Be ions and the P-type ions are Si ions. The method of claim 7 or 8, wherein the ion implantation acceleration energy of the Be ions is 200 KeV, and the ion implantation acceleration energy of the Si ions is 1 MeV. 7. A method according to claim 6, wherein the electrically isolated region (6) is formed by a proton bombardment method. The method of manufacturing a horizontal field semiconductor optical switching element according to claim 6, wherein the metal film deposited for forming the electrode contact (7) is Au.