JP3661801B2 - Dislocation density measurement method for II-VI group compound semiconductor single crystal - Google Patents

Description

[0001]
[Industrial application fields]
The present invention relates to a method for measuring a dislocation density in a II-VI group compound semiconductor single crystal such as zinc selenide (ZnSe), which is expected as a material for blue light-emitting devices.
[0002]
[Prior art]
Zinc selenide (ZnSe), a type of II-VI group compound semiconductor, has been conventionally produced by vapor phase growth or high pressure melting, but single crystals obtained by these production methods are not crystallographically. It is incomplete and includes an incomplete part in the crystal called dislocation. The number of dislocations per unit area is called the dislocation density, which has a close relationship with the emission lifetime of the blue light emitting device and is very important in determining whether it is suitable as an epitaxial growth substrate. One of the characteristics.
[0003]
Until now, as a method for measuring the dislocation density of a ZnSe single crystal, a method for measuring the (111) plane and the (110) plane of a single crystal is known, but a measurement method for the (100) plane is still known. Even when the crystal orientation for epitaxial growth is the (100) plane, information on the dislocation density cannot be directly obtained from the single crystal substrate coordinated in that orientation.
[0004]
For this reason, for example, two types of slicing are necessary, that is, orientation orientation of a substrate for epitaxial growth and orientation orientation of a single crystal for investigation of dislocation density from a large-diameter and long bulk crystal obtained by a high pressure melting method. It was.
[0005]
[Problems to be solved by the invention]
As described above, the conventional dislocation density measurement method cannot directly measure the dislocation density on the (100) plane, and thus can be used as the substrate itself, for example, when epitaxial growth is performed on the ZnSe single crystal substrate (100) plane. It has a drawback that it cannot be determined in a short time whether or not it is a simple substrate.
[0006]
Accordingly, an object of the present invention is to provide a method for directly measuring the dislocation density on the (100) plane of a II-VI group compound semiconductor crystal including ZnSe, which is expected as a material for blue light-emitting devices.
[0007]
[Means for Solving the Problems]
As a result of diligent research to achieve the above object, the present inventors have obtained a clear etched image of the dislocation portion when the (100) plane of a ZnSe single crystal substrate is etched using a dilute bromine methanol solution. The present inventors have found that the dislocation density can be measured and that this method can be applied to II-VI group compound semiconductor single crystals other than ZnSe single crystals.
[0008]
That is, according to the present invention, first, a substrate obtained by slicing the (100) plane of a ZnSe single crystal is subjected to surface polishing and mirror etching, and then immersed in a bromine-methanol solution. dislocation density measuring method of ZnSe single crystal, characterized in that to measure the dislocation on the (100) plane from the etched image that is;. second, the bromine methanol solution 0 1 to 1% by volume of bromine A dislocation density measurement method for a ZnSe single crystal according to the first aspect, which is a methanol solution, is provided.
[0009]
[Action]
A ZnSe single crystal substrate used as a raw material in the present invention is obtained by first growing a ZnSe polycrystal by a high pressure melting method on a seed crystal as a seed crystal using a vertical Bridgman furnace or a vertical annealing furnace. That is, in the former, the crucible containing the melt is lowered in an electric furnace with a temperature gradient to grow the crystal, and in the latter, the crucible is placed in an electric furnace with a temperature gradient in the vertical direction and the temperature gradient remains. Gradually cool and precipitate crystals from the bottom of the crucible.
[0010]
Next, this single crystal cut in the (100) direction with a slicer is polished by lapping performed with free abrasive grains interposed, and further mirror-etched to cut the surface into a predetermined shape for mirror finishing.
[0011]
In the present invention, the surface of the substrate is etched by immersing the single crystal substrate in a 0.1% by volume bromine methanol solution. As the etching conditions, the solution is stirred at room temperature for about 80 to 150 seconds. Since a clear etched image is obtained, the dislocation density can be measured from this.
[0012]
【Example】
FIG. 1 is a schematic cross-sectional view showing a single crystal substrate etching apparatus used in this example, and FIG. 2 is a micrograph showing a corroded portion after etching a ZnSe single crystal substrate. FIG. FIG. 5B is an enlarged view of 1000 times, and will be described below with reference to these drawings.
[0013]
A sample obtained by slicing a (100) plane from a ZnSe single crystal obtained in advance by the high-pressure melting method, cutting a 5 mm square × 1 mm thick substrate, polishing the surface of the substrate, and then performing a mirror etching process. A substrate was used.
[0014]
The Teflon basket 2 is reacted so that the ZnSe substrate 5 is immersed in a 1% by volume bromine methanol solution 6 at room temperature (about 20 ° C.) placed in the reaction tank 1 of the single crystal substrate etching apparatus shown in FIG. Set in the bath.
[0015]
A stirrer 3 was previously provided at the bottom of the reaction tank, and the stirrer 3 was rotated at a speed of 250 rpm for 120 seconds with a magnetic stirrer 4 at the bottom of the reaction tank to perform an etching process.
[0016]
The ZnSe substrate subjected to the above etching treatment was taken out from the reaction vessel, ultrasonically washed in methanol and dried, and then a corroded portion (dislocation portion) was observed with a Nomarski differential interference microscope.
[0017]
The observed dislocation portion on the ZnSe substrate is shown as a photograph 400 times as large as FIG. 2A and 1000 times as large as FIG. 2B. From these, the dislocation density per unit area could be easily measured. .
[0018]
In addition, although the etching process was tried also about II-VI group compound semiconductor single crystal other than ZnSe, the result almost the same as the case of ZnSe was obtained.
[0019]
【The invention's effect】
As described above, there has been no means for directly measuring the dislocation density in the (100) plane of a conventional II-VI group compound semiconductor single crystal. However, according to the method of the present invention, (100) Dislocations that are clearly clarified by etching the surface can be measured, so the dislocation density of the (100) surface can be measured in a short time, and the suitability of the II-VI group semiconductor as an epitaxial growth substrate can be easily determined. It became so.
[Brief description of the drawings]
FIG. 1 is a schematic cross-sectional view showing a single crystal substrate etching apparatus used in Examples.
FIGS. 2A and 2B are micrographs showing a corroded portion after etching a ZnSe single crystal substrate. FIG. 2A is an enlarged photograph of 400 times, and FIG.
[Explanation of symbols]
DESCRIPTION OF SYMBOLS 1 Reaction tank 2 Basket 3 Stirrer 4 Magnetic stirrer 5 ZnSe substrate 6 Bromine methanol solution

Claims (2)

The substrate obtained by slicing the (100) plane of the ZnSe single crystal was subjected to surface polishing and mirror etching, and then etched by immersing in a bromine methanol solution. From the obtained etched image, the ( 100) A dislocation density measuring method for a ZnSe single crystal characterized by measuring dislocations on a plane. The bromine methanol solution is 0. A 1 to 1 volume% bromine methanol solution, the dislocation density measuring method of ZnSe single crystal according to claim 1, wherein.

Images