JP3753337B2 - Semiconductor for light emitting device and method for manufacturing the same - Google Patents

Description

[0001]
BACKGROUND OF THE INVENTION
The present invention relates to a semiconductor for a light-emitting element that is a material for a light-emitting element such as a light-emitting diode and a semiconductor laser, and a method for manufacturing the same.
[0002]
[Prior art]
Compound semiconductors doped with rare earth elements have been widely studied for application to light-emitting elements and elucidation of light-emitting mechanisms. Among them, those using erbium (Er) as the rare earth element _have a light emission wavelength of ⁴ I _13/2 → ⁴ I _15/2 of the Er ³⁺ 4f shell that matches the minimum loss wavelength of 1540 nm of the silica-based fiber. It is highly expected as a material for light emitting elements for optical communication.
[0003]
[Problems to be solved by the invention]
However, when erbium is added to a compound semiconductor having a narrow band gap, the emission intensity is greatly reduced as the temperature rises due to the narrow band gap, so that it is difficult to emit light at room temperature. For this reason, attempts have been made to add erbium to a compound semiconductor having a wide band gap, but sufficient results have not been obtained so far.
[0004]
OBJECT OF THE INVENTION
An object of the present invention is to achieve a sufficient luminous intensity when added to erbium in the broad compound semiconductor having the bandgap, semiconductor and its light emitting element thereby realizing a suitable light emitting element for use at room temperature It is to provide a manufacturing method.
[0005]
[Means for Solving the Problems]
The semiconductor for a light emitting device according to the present invention is composed of a porous compound semiconductor containing a rare earth element as a light emission center. A method for producing a semiconductor for a light-emitting device according to the present invention is a method for producing a semiconductor for a light-emitting device according to the present invention, comprising a first step of converting a single crystal compound semiconductor into a porous compound semiconductor by an anodization method, A second step of attaching a rare earth element to the porous compound semiconductor and a third step of applying an annealing treatment (annealing) to the porous compound semiconductor to which the rare earth element is attached are provided.
[0006]
The rare earth element is erbium (Er), the compound semiconductor is gallium phosphide (GaP). In this case, the second step may electrochemically attach erbium to the porous gallium phosphide. More specifically, the gallium phosphide is made porous by electrolyzing an erbium trichloride solution. It is also possible to attach erbium electrochemically. In this case, the third step may be performed at an annealing temperature of 900 to 1100 ° C. and an annealing time of 10 to 15 minutes.
[0007]
In the second step, the rare earth element may be attached to the porous compound semiconductor by sputtering or vapor deposition .
[0008]
DETAILED DESCRIPTION OF THE INVENTION
One embodiment of a semiconductor for a light emitting device and a method for producing the same according to the present invention will be described below.
[0009]
The light-emitting element semiconductor of this embodiment is manufactured by the following steps 1 to 4 as shown in the process chart of FIG. First, as a gallium phosphide single crystal, an n-type GaP substrate (hereinafter, simply referred to as “GaP substrate”) having a plane orientation (111) doped with 3 × 10 ¹⁷ cm ^{−3 of} sulfur (S) is prepared. 1 . A gold-germanium (Au—Ge) alloy is deposited on the back surface of the GaP substrate by vacuum deposition. The composition of the Au—Ge alloy is 88 wt% Au and 12 wt% Ge. The degree of vacuum during vacuum deposition is 1 × 10 ⁻⁶ Torr or more. 2 . The surface of the GaP substrate is made porous by anodization. 3 . Erbium is electrochemically attached to the porous GaP substrate. 4 . An annealing process is performed on the GaP substrate to which erbium is adhered. The annealing temperature is constant in the range of 700 to 1100 ° C., and the annealing time is 10 to 15 minutes in an argon (Ar) atmosphere. The annealing was performed in a state where the surface of the porous GaP substrate (the surface made porous) and the surface of the normal GaP substrate face each other.
[0010]
Step 2 will be described in detail with reference to FIG. The beaker 10 is made of polytetrafluoroethylene, and a through hole 10b is formed in the bottom surface 10a. The etching solution 12 in the beaker 10 is obtained by diluting 48 wt% hydrofluoric acid (HF) to 50% with ethyl alcohol (C ₂ H ₅ OH). The bottom surface 10 a of the beaker 10 faces the surface 16 a of the GaP substrate 16 through the O-ring 14. Therefore, the etching solution 12 is in contact with the surface 16a of the GaP substrate 16 through the through hole 10b. The back surface 16b of the GaP substrate 16 is bonded to the copper plate 18 with silver paste or the like. The anodization was performed under the conditions where the current source 22 was connected so that the copper plate 18 was the anode and the platinum plate 20 was the cathode, the current density was 20 mA / cm ² , the time was 10 minutes, and no illumination was applied. Thereby, the surface 16a of the GaP substrate 16 was made porous. Note that indoor lighting, a xenon lamp, a mercury lamp, or the like may be used instead of no lighting.
[0011]
Step 3 will be described in detail with reference to FIG. The erbium trichloride solution 30 in the beaker 10 is obtained by dissolving erbium trichloride (ErCl ₃ ) in ethyl alcohol (C ₂ H ₅ OH). An erbium trichloride solution 30 is brought into contact with the surface 16a of the porous GaP substrate 16, and a current source 22 is connected so that the copper plate 18 is a cathode and the platinum plate 20 is an anode, as opposed to step 2. The erbium chloride solution 30 was electrolyzed. As a result, erbium was deposited on the surface 16 a of the GaP substrate 16.
[0012]
In Steps 2 and 3 , the etching solution 12 or the erbium trichloride solution 30 is brought into contact only with the surface 16 a of the GaP substrate 16 by using the O-ring 14. Therefore, compared with the method of immersing the entire GaP substrate 16 in the etching solution 12 or the erbium trichloride solution 30, cleaning is easy and a protective film on the back surface 16b side of the GaP substrate 16 is unnecessary.
[0013]
In this way, a sample was prepared. Four types of samples were prepared according to the annealing temperature: [A] 1000 ° C, [b] 900 ° C, [C] 800 ° C, and [D] 700 ° C. For comparison, a single crystal GaP substrate with erbium ion-implanted was prepared as a sample [e], and a single crystal GaP substrate with erbium and nitrogen ions implanted as a sample [f].
[0014]
The results of evaluating these samples by the photoluminescence (hereinafter referred to as “PL”) method are shown in FIGS. In the evaluation by the PL method, a sample is attached to a cryostat, the sample is excited by light of a wavelength of 488 nm of an argon ion laser, the PL light emitted from the sample is dispersed by a double monochromator, and cooled by liquid nitrogen (pin diode) ) By receiving the PL spectrum.
[0015]
4 and 5 show the evaluation results of the samples [A] to [D], that is, the annealing temperature dependency. FIG. 4 shows a sample temperature, that is, a measurement temperature of 20K, and FIG. 5 shows a measurement temperature of 300K. The following can be seen from FIGS. (1) The higher the annealing temperature, the higher the PL intensity near 1540 nm. (2) When the annealing temperature is 800 ° C. (sample [C]) or lower, erbium is less likely to be the emission center. (3) Although not shown, when the annealing temperature is 1100 ° C. or higher, the PL strength tends to decrease. (4) Therefore, the annealing temperature is preferably 900 ° C. (sample [b]) or higher, more preferably 1000 ° C. (sample [b]) or higher, and preferably 1100 ° C. or lower. It is considered that erbium deposited on the surface of the GaP substrate diffuses into the GaP substrate by such an annealing temperature and forms an emission center.
[0016]
FIG. 6 shows the results of the PL spectrum at the measurement temperatures of 20K and 300K for the sample [A]. From FIG. 6, a large PL intensity is recognized in the vicinity of 1540 nm regardless of the measurement temperature.
[0017]
FIG. 7 shows the results of evaluating the measurement temperature dependence of the sample [A]. In FIG. 7, ▪ is the PL intensity at a wavelength of 1538.8 nm, and Δ is the PL intensity at a wavelength of 1506.6 nm. Further, ◯ is the PL intensity at a wavelength of 1538.5 nm for the sample [e], and ● is the PL intensity at a wavelength of 1528.3 nm for the sample [f]. As is clear from FIG. 7, the sample [A] has a much higher PL intensity at room temperature than the samples [E] and [F]. The light emission state of the sample [A] was surface light emission corresponding to the entire inside of the O-ring 14.
[0018]
The reason why the sample [A] emitted light very strongly at room temperature is considered as follows. (1) Erbium is directly excited, not excited from gallium phosphide (matrix). (2) If the excitation is from gallium phosphorus, the Auger effect generated from the excited erbium ions is small, or the back energy transfer to the gallium phosphorus is small. (3) Quantum effect by porous gallium phosphide is influencing. (4) A large amount of erbium optically activated in gallium phosphide.
[0019]
Needless to say, the present invention is not limited to the above embodiment. For example, a light element such as oxygen, fluorine, or hydrogen may be introduced into the gallium phosphide single crystal in advance. In step 2 shown in FIGS. 2 and 3, instead of the platinum plate 20 may be parallel platinum plate 32 (FIG. 8) on the surface 16a of the GaP substrate 16. In this case, since the electric lines of force generated between the platinum plate 32 and the GaP substrate 16 are parallel, more uniform processing is possible. Similarly, in steps 2 and 3 , the concentration of the etching solution 12 or the erbium trichloride solution 30 is made uniform by stirring the etching solution 12 or the erbium trichloride solution 30 in the beaker 10 using a stirrer or the like. Good. In this case, since the concentration of the etching solution 12 or the erbium trichloride solution 30 is uniform, more uniform processing is possible.
[0020]
【The invention's effect】
According to the semiconductor for a light emitting device and the method for manufacturing the same according to the present invention, the inclusion of erbium as the emission center in the porous gallium phosphide allows the PL at room temperature as compared with the conventional compound semiconductor containing erbium. Strength can be improved dramatically. Accordingly, since the band gap of gallium phosphide is wide, high light emission efficiency can be maintained even at room temperature, and thus a light emitting element suitable for use at room temperature can be realized.
[ 0021 ]
The lattice constant of gallium phosphide is very close to that of silicon. Therefore, since high-quality single-crystal gallium phosphide can be formed on the single-crystal silicon substrate, a highly integrated optoelectronic integrated circuit (OEIC) can be realized by making the single-crystal gallium phosphide porous.
[ 0022 ]
According to the method for manufacturing a semiconductor for a light-emitting element according to any one of claims 4 to 7, by introducing erbium electrochemically into the porous gallium phosphide, the equipment is cheaper than ion implantation, MBE, MOCVD, etc. Erbium can be easily introduced into gallium phosphide. Therefore, the method for manufacturing a semiconductor for a light emitting device according to claims 4 to 7 is suitable for mass production.
[Brief description of the drawings]
FIG. 1 is a process diagram showing an embodiment of a method for producing a semiconductor for a light emitting device according to the present invention.
FIG. 2 is an explanatory diagram showing an example of a process 2 in the process diagram of FIG. 1;
FIG. 3 is an explanatory diagram showing an example of a process 3 in the process diagram of FIG. 1;
FIG. 4 is a graph showing the results of evaluating the annealing temperature dependency of an embodiment of a light emitting device semiconductor according to the present invention.
FIG. 5 is a graph showing the results of evaluating the annealing temperature dependency of an embodiment of a light emitting device semiconductor according to the present invention.
FIG. 6 is a graph showing the results of evaluating the measurement temperature dependency of an embodiment of a light emitting device semiconductor according to the present invention.
FIG. 7 is a graph showing the results of evaluating the measurement temperature dependence of one embodiment of a semiconductor for a light emitting device according to the present invention.
FIG. 8 is an explanatory diagram showing another example of steps 2 and 3 in the step diagram of FIG. 1;
[Explanation of symbols]
10 Beaker 12 Etching solution 14 O-ring 16 GaP substrate 18 Copper plate 20, 32 Platinum plate 22 Current source 30 Erbium trichloride solution

Claims (7)

A semiconductor for a light-emitting element , comprising porous gallium phosphide, in which single crystal gallium phosphide is made porous by anodization, and erbium adhering to the porous surface becomes an emission center by annealing treatment . The semiconductor for a light emitting device according to claim 1, wherein the single crystal gallium phosphide has a plane orientation (111). A method for producing a semiconductor for a light emitting device according to claim 1,
A first step of converting single-crystal gallium phosphide into porous gallium phosphide by anodization, a second step of attaching erbium to the porous gallium phosphine, and an annealing treatment for the porous gallium phosphide to which the erbium is attached A method for manufacturing a semiconductor for a light-emitting element, comprising three steps. The method for manufacturing a semiconductor for a light emitting device according to claim 3, wherein the single crystal gallium phosphide has a plane orientation (111). 5. The method for manufacturing a semiconductor for a light-emitting element according to claim 3 , wherein the second step is to electrochemically attach the erbium to the porous gallium phosphide.   6. The method of manufacturing a semiconductor for a light-emitting element according to claim 5, wherein the second step is to electrochemically attach the erbium trichloride to the porous gallium phosphide by electrolyzing an erbium trichloride solution. 5. The method for manufacturing a semiconductor for a light-emitting element according to claim 3 , wherein the third step has an annealing temperature of 900 to 1100 ° C. and an annealing time of 10 to 15 minutes.

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