CN1424794A - Semiconductor laser with continuously adjustable wavelength and preparation thereof - Google Patents

Abstract

The invention belongs to the technical field of photonic materials, in particular to a quantum dot semiconductor laser with continuously adjustable wavelength and a preparation method thereof. It is a method of preparing a self-organized quantum dot array by focused ion beam sputtering, and forms a quantum dot array whose quantum dot size continuously changes along one-dimensional direction on the surface of a semiconductor. Then, according to the quantum confinement effect, the continuous tunability of the optical wavelength is realized. The invention reduces the workload of semiconductor laser material selection, accurately obtains the required light wavelength, and greatly promotes the development of optoelectronic devices and photonic devices.

Description

A semiconductor laser with continuously adjustable wavelength and its preparation method

technical field

The invention belongs to the technical field of photonic materials, and in particular relates to a semiconductor laser with continuously adjustable wavelength and a preparation method thereof.

Background technique

Semiconductor lasers have the characteristics of small size, wide operating temperature range, and low excitation current, and are widely used in the design of optoelectronic devices and photonic devices. Its inventors Zh.I.Alferov of the former Soviet Union and H.Kroemer of the United States won the 2000 Nobel Prize in Physics for this. Semiconductor lasers emit only one wavelength of light. Different optoelectronic devices and photonic devices need to use light of different wavelengths, and correspondingly require semiconductor lasers of different wavelengths. At present, semiconductor lasers of various wavelengths are mainly developed by selecting different materials, which brings great inconvenience to the application of semiconductor lasers. Moreover, due to the discontinuity of solid energy level changes, for example: the optical wavelength of InAs quantum dot semiconductor lasers It is 1080nm; the nano-Si laser is about 750nm, etc., often cannot accurately obtain the required light wavelength.

Contents of the invention

The purpose of the present invention is to propose a semiconductor laser with continuously adjustable wavelength and its preparation method, so as to conveniently and accurately meet the requirements of optoelectronic devices and photonic devices for different wavelength beams.

The wavelength continuously adjustable semiconductor laser proposed by the present invention is composed of the following parts in order: bottom electrode, n-type semiconductor, semiconductor laser material, p-type semiconductor, upper electrode, split electrode and power supply, and its structure is shown in Figure 1 . Among them, the quantum dots of the laser material sandwiched between p-type and n-type semiconductors have excited characteristics, and the surface of the material has multiple parallel quantum dot bands. The quantum dots in each quantum dot band have the same size and are evenly distributed. The size of the quantum dots between the bands is different, and from left to right, the size of the quantum dots changes monotonously (continuously increasing from left to right in FIG. 2 ), as shown in FIG. 2 .

In the present invention, the parallel quantum dot bands on the surface of the semiconductor laser material can generally be 3-10, or more. Wherein, the size of quantum dots is generally less than 100 nm.

In the present invention, the upper electrode is composed of multiple electrodes, and each quantum dot strip corresponds to one electrode. The electrodes are strip-shaped, basically the same (slightly smaller) in shape as the corresponding quantum dot strip, and positioned directly above the quantum dot strip; each electrode is made of an electrical insulating material, and the gap width is greater than that of the split-shaped electrode. The bottom electrode is a continuous metal layer.

The principle of the present invention is as follows: Due to the semiconductor luminescent material used, its quantum dot has the characteristic of stimulated emission. As the split electrode moves from left to right, the laser emits a beam of continuously varying wavelength due to quantum confinement effects. This effect indicates that when the size of the solid is small to a certain extent (such as nano-scale quantum dots), the distance between the energy levels of the solid is determined by the size of the quantum dots. The energy level spacing determines the wavelength of the emitted light. Therefore, if the quantum dot size can be continuously adjusted, the energy level spacing can be continuously adjusted, thereby obtaining a luminescent material with continuously adjustable wavelength. In the present invention, the luminescent material has the characteristic of stimulated emission, and the laser material with continuously adjustable wavelength is obtained. Due to the method of forming a self-organized quantum dot array using ion beam sputtering, the size of the quantum dots can be precisely controlled.

In the present invention, the above-mentioned semiconductor laser material can be one layer, as shown in FIG. 1, or multiple layers, that is, a multi-layer quantum dot semiconductor laser with continuously adjustable wavelength can be obtained, thereby greatly increasing the luminous intensity. The number of layers is generally below 10. Its preparation can be carried out in combination with coating technology, that is, the same layer of semiconductor material is plated on a single layer of material, and on this layer of film, an array of quantum dots exactly the same as that of the lower layer of film is produced. This process can be repeated until the desired number of layers is reached. Its side view is shown in Figure 3.

The present invention also proposes a method for preparing the above-mentioned quantum dot semiconductor laser with continuously adjustable wavelength, and the specific steps are as follows:

1. First select the semiconductor material whose known quantum dot luminescent wavelength is close to the required wavelength value. The so-called quantum dots refer to atomic group particles with a size smaller than 100nm.

2. On the doped n-type semiconductor with a flat surface (atomic level or close to atomic level), plate a layer of flat semiconductor film with a thickness of about 1 micron. Coating method can adopt the focused ion beam sputtering method that inventor develops recently to prepare self-organized quantum dot array, and it has the characteristics of accurately controlling quantum dot size, (M.Lu (Lu Ming), X.J.Yang, s.s.Perry, J.W. Rabalais, Applied Physics Letters, 80, 2096 (2002)). Using this technology, a quantum dot array as shown in Figure 2 is prepared on the surface of the semiconductor thin film. If the preparation conditions permit, the more the number of quantum dot bands and the smaller the size difference of quantum dots between adjacent bands, the better the wavelength continuity of the obtained laser. There can be 3-10 quantum dot strips on one layer. In addition, combined with coating technology, it is also possible to prepare multiple layers of laser material films with quantum dot bands as shown in Figure 3 . Generally speaking, the number of layers can be less than 10 layers.

3. On the above-mentioned laser material with parallel quantum dot strips on the surface, cover a layer of doped p-type semiconductor thin film. As shown in Figure 1. The functions of p-type and n-type semiconductors are 1) as optical waveguides, confining light to the layer between p-type and n-type semiconductors; 2) by injecting carriers, the intensity of light emission can be increased.

4. Plating the upper electrode and the interval electrical insulating material, and then plating the bottom electrode which is continuously distributed.

5. Both ends of the semiconductor film material are polished to form a resonant cavity.

6. Coupled with a split electrode and a power supply, it is assembled into a laser. Figure 1 shows an electrically excited laser. The laser emits a beam of continuously varying wavelength as the split electrode moves from left to right.

The above steps 2-4 are carried out in a vacuum environment.

The present invention prepares the quantum dot laser film material with continuously adjustable wavelength, which can be guaranteed by the following four points: 1) the selected semiconductor material, whose quantum dots are known to have stimulated emission characteristics; 2) the focused ion beam sputtering developed by us The method of preparing a self-organized quantum dot array can precisely control the size of the quantum dots; 3) the quantum confinement effect ensures that the wavelength of the light emitted by the quantum dots changes monotonously with the size of the quantum dots, which has also been proved by experiments; 4 ) The quantum dots produced by the focused ion beam sputtering method have been proved to be nano-single crystals, so the non-radiative recombination centers caused by defects have little effect on light emission.

In the present invention, a focused inert ion beam is used to be incident on the sample surface (perpendicular to the sample surface), and the ion sputtering parameters are adjusted to form the quantum dot array shown in FIG. 2 . The size of the quantum dot strips can be determined according to the size of the silicon substrate and the number of quantum dot strips. Generally, it can be: the bandwidth is 2-3 mm, the strip length is about 4-6 mm, and the distance between the strips is about 0.8-1.2 mm. The electrode width is smaller than the spacing between the ribbons, and its length is the same as the quantum dot ribbon length.

In the present invention, the quantum dots of the semiconductor samples used are known to have stimulated emission characteristics, such as: InAs (1080nm), InGaAs (1100nm), Si (750nm), ZnS (620nm), CdSe (540nm), ZnSe (445nm) wait. The values in brackets are the known emission wavelengths of quantum dots. The surface of the sample needs to be flat (at the atomic level or close to the atomic level).

In the present invention, combined with coating technology (such as ion sputtering deposition, laser ablation deposition, etc.), a multi-layer semiconductor laser material with continuously adjustable wavelength is prepared.

In the present invention, p-type and n-type semiconductors are doped from corresponding light-emitting semiconductor samples.

The semiconductor laser with continuously adjustable wavelength can be prepared by the invention, which can reduce the material selection workload of the semiconductor laser, can accurately obtain the required wavelength, and greatly promotes the development of optoelectronic devices and photonic devices.

Description of drawings

Figure 1 Schematic diagram of the structure of a single-layer continuously tunable semiconductor laser.

Fig. 2 Schematic representation of quantum dot bands on the surface of a single-layer semiconductor laser material with continuously tunable wavelength.

Fig. 3 is a schematic diagram of the composition of multi-layer quantum dot semiconductor materials with continuously tunable wavelength.

Figure 4 is a schematic diagram of the upper electrode insulation interval.

Figure 5 is a diagram of the upper electrode structure.

In the figure: 1 is the bottom electrode, 2 is the n-type semiconductor, 3 is the quantum dot semiconductor laser material with continuously adjustable wavelength, 4 is the p-type semiconductor, 5 is the upper electrode, 6 is the split electrode, and 7 is the upper electrode layer The insulation gap, 8 is the power supply.

Detailed ways

The present invention is further described below by way of example.

Embodiment: Take the preparation of a 5-layer quantum dot GaAs laser with continuously adjustable wavelength as an example.

1. On the n-type GaAs, use the coating technology to plate a GaAs film with a thickness of 1 micron.

2. Use the focused Ar ion beam generated by the sputtering ion gun to sputter the surface of the GaAs film at a positive incident angle. Quantum dot strip) × 5 mm (parallel to the quantum dot strip) range scanning. The ion gun exit electrode is about 7 cm away from the sample. The sample temperature is controlled at less than 100°C. The size of the quantum dots is controlled by tuning the ion energy. Ion energy ranges from 100-1500 electron volts, or according to actual needs. According to the pattern in Figure 1, prepare each quantum dot band from left to right, that is, first use the lowest energy to prepare the leftmost quantum dot band, then move the sample 1 mm to the left, and then adjust the ion energy appropriately to prepare the second band Quantum dot ribbon, this process continues until the preparation of the rightmost quantum dot ribbon is completed. At this point, the thickness of the GaAs film has been "cut" to 0.1-0.3 microns.

3. On the first layer of GaAs, plate a GaAs film with a thickness of 1 micron, and then continue to step 2, and so on, until the fifth layer of GaAs forms a quantum dot array as shown in Figure 1.

4. On the fifth layer of GaAs, a GaAs film with a thickness of 0.5 microns is plated as a protective layer.

5. On the sixth layer of GaAs, cover it with p-type GaAs.

6. On the p-type GaAs, using the template, plate SiO ₂ as the insulating spacer of the upper electrode. As shown in Figure 4:

7. On the p-type GaAs, use the yin-yang symmetric template as in step 6, and plate Ni/Au as the upper layer electrode. As shown in Figure 5.

8. The whole material is rapidly heated in air at 400°C for 30 seconds to form a transparent electrode.

9. Both ends of the multi-layer GaAs film are polished to form a resonant cavity.

10. Assemble a multilayer quantum dot GaAs laser with continuously adjustable wavelength according to Fig. 1 .

Claims (7)

1. A semiconductor laser with continuously adjustable wavelength is characterized in that it is composed of the following parts in sequence: bottom electrode, n-type semiconductor, semiconductor laser material, p-type semiconductor, upper electrode, split electrode and power supply, wherein, sandwiched The laser material between p-type and n-type semiconductors has excited quantum dots. The surface of the material has multiple parallel quantum dot bands. The quantum dots in each quantum dot band have the same size and uniform distribution. The quantum dot sizes of are different, and from left to right, the quantum dot size shows a continuous monotonous change. 2. The semiconductor laser according to claim 1, characterized in that there are 3-10 quantum dot bands on the surface of the semiconductor laser material. 3. The semiconductor laser according to claim 1 or 2, characterized in that the bandwidth of said quantum dot strips is 2-3 mm, the strip length is 4-6 mm, and the distance between the strips is 0.8-1.2 mm. 4. A semiconductor laser according to claim 1 or 2, characterized in that the number of layers of said semiconductor laser material does not exceed 10. 5. The semiconductor laser according to claim 1, wherein the upper layer electrode is composed of multiple electrodes, and each quantum dot strip corresponds to an electrode; the electrode is strip-shaped, and its shape is basically the same as that of the corresponding quantum dot strip, and its position It is located directly above the quantum dot strip; between the electrodes is an electrical insulating material, and the gap width is greater than the width of the split-shaped electrode. 6. A method for manufacturing a continuously adjustable wavelength semiconductor laser according to claims 1-5, characterized in that the specific steps are as follows: (1) First select the semiconductor material whose known quantum dot luminescent wavelength is close to the required wavelength value; (2) On the doped n-type semiconductor with a flat surface, a layer of flat semiconductor laser material film with a thickness of about 1 micron is plated, and a self-organized quantum dot array is prepared by focused ion beam sputtering , to obtain quantum dot bands; there are 3-10 quantum dot bands on one layer; (3) On the above-mentioned laser material with parallel quantum dot bands on the surface, cover a doped p-type semiconductor thin film; (4) plate the upper electrode and the electrical insulating material at intervals, and then plate the bottom electrode which is continuously distributed; (5) Both ends of the semiconductor film material are polished to form a resonant cavity; (6) Coupled with a split-shaped electrode and a power supply, it is assembled into a laser. 7. The preparation method according to claim 6, characterized in that combining the coating technology to prepare multiple layers of laser material film layers with the same quantum dot band, the number of layers is less than 10.

Images