JP2712257B2 - How to grow zinc selenide - Google Patents

Description

Description: TECHNICAL FIELD The present invention relates to a method for growing zinc selenide (ZnSe).

[Summary of the Invention]

The present invention relates to a method for growing zinc selenide in which zinc selenide containing oxygen as a dopant is grown by molecular beam epitaxy, wherein ZnO is used as an oxygen source.
And a partial pressure of about 1 × 10 ⁻⁹ Torr, whereby p-type zinc selenide can be easily obtained.

[Conventional technology]

ZnSe is a type of II-VI compound semiconductor, and has attracted attention as a blue light emitting element material. This ZnSe can be obtained only in n-type by ordinary crystal growth. For this reason, various attempts have been made to obtain p-type ZnSe. Conventionally, as a p-type dopant for obtaining the p-type ZnSe, lithium (Li), sodium (Na), arsenic (As), phosphorus (P),
Attempts have been made to use nitrogen (N) and the like.

[Problems to be solved by the invention]

However, Li and Na are mobile in the crystal,
There are drawbacks such as entry into interstitial sites of the crystal and acting as donors. Since As and P have a deep acceptor level, it is necessary to increase the doping amount.
There is a disadvantage that (self-activated) defects (combined defects of Zn vacancies and impurities) are likely to occur. Further, N has a relatively shallow acceptor level of about 110 meV.
The disadvantage is that the rate of incorporation into the crystal during crystal growth is small and doping is difficult. To give a specific example,
Even when the N partial pressure during growth is about 1 × 10 ⁻⁵ Torr, the N concentration in ZnSe is about 10 ⁻¹⁵ to 10 ⁻¹⁶ cm ⁻³ .

As described above, all of the p-type dopants that have been conventionally used have problems, and as a result, it has been difficult to obtain p-type ZnSe.

Accordingly, an object of the present invention is to easily obtain p-type ZnSe.

[Means for solving the problem]

The present invention relates to a method for growing zinc selenide (ZnSe) containing oxygen (O) as a dopant, wherein the oxygen source is
It is characterized by using a molecular beam of ZnO and making its partial pressure approximately 1 × 10 ⁻⁹ Torr.

[Action]

According to the above-mentioned means, since oxygen (O) is a dopant having the same valence as selenium (Se), the acceptor level is as shallow as about 90 meV. For this reason, the doping amount of oxygen as a dopant can be reduced, so that SA defects hardly occur. In addition, this oxygen hardly moves in the crystal and is easily taken into the crystal during crystal growth.
Furthermore, oxygen can be doped at a high concentration even though the partial pressure of ZnO is as low as about 1 × 10 ⁻⁹ Torr, so that doping is easy.

As described above, p-type zinc selenide can be easily obtained.

〔Example〕

Hereinafter, an embodiment of the present invention will be described with reference to the drawings.

As shown in FIG. 1, in the present embodiment, for example, an n-type gallium arsenide (GaAs) substrate 2 is arranged in a molecular beam epitaxy (MBE) apparatus 1 kept in an ultra-high vacuum state, and Zn, Z generated by Knudsen Cells C ₁ , C ₂ and C ₃ constituting the evaporation sources of Se and ZnO
The GaAs substrate 2 is irradiated with molecular beams of n, Se and ZnO. Thus, an O-doped ZnSe epitaxial film 3 is grown on the GaAs substrate 2. The base pressure of the MBE apparatus 1 is, for example, 10 ^-10 to 10 ^-11 Torr, and the substrate temperature is, for example,
It is around 250 ° C. In addition, Knudsen cells C ₁ , C ₂ and C
The standard temperatures of ₃ , e.g., 250 ° C, 130 ° C and 700 ° C respectively
° C. In this case, the partial pressure of ZnO is, for example, 1 × 10 ⁻⁹ Torr.
It is about. The growth time is, for example, 2 hours, and the film thickness of the ZnSe epitaxial film 3 grown thereby is, for example, about 3 μm.

FIG. 2 shows O-doped ZnSe grown as described above.
4 shows an example of a photoluminescence spectrum of the epitaxial film 3. FIG. 3 shows an example of a photoluminescence spectrum of an N-doped ZnSe epitaxial film using ion-implanted N as a dopant.
It is measured for comparison with the figure. These photoluminescence spectra are obtained by using He-
It was measured using a Cd laser (wavelength 3250 °), and the measurement was performed at 4K. In these photoluminescence spectra, peak a is light emission by a bound exciton, and peak b is so-called donor
Light emission due to acceptor transition. Note that this peak b
Peak c that appears on the longer wavelength (lower energy) side than
-E are so-called phonon replicas.

Comparing FIG. 2 with FIG. 3, the peak b appears at a wavelength of about 4600 ° in FIG. 3, whereas the peak b in FIG.
It appears at around 4550Å, and is shifted to the short wavelength (high energy) side by about 50Å (about 27meV in energy conversion). This means that the O acceptor level in the O-doped ZnSe epitaxial film 3 is about 27 meV lower than the N acceptor level in the N-doped ZnSe epitaxial film.
Indicates shallowness. Therefore, the acceptor level of O is about
About 90meV and shallow. Since the acceptor level is shallow, the doping amount of O can be reduced, and accordingly, SA defects are less likely to occur.

Next, FIG. 4 shows the O-doped layer grown as described above.
The result of measuring the distribution profile of O in the ZnSe epitaxial film 3 by secondary ion mass spectrometry (SIMS) is shown.
Note that Cs ⁺ was used as a primary ion.

From FIG. 4, it is considered that under the epitaxial growth conditions of a substrate temperature of 250 ° C. for 2 hours, O in the ZnSe epitaxial film 3 hardly diffuses during the growth. That is, it can be seen that O in the ZnSe epitaxial film 3 hardly moves. The secondary ion ⁽¹⁶ O ^-) intensity of 9.3 × 10 ³ c /
s, the O in the ZnSe epitaxial film 3
Is about 3.6 × 10 ¹⁸ cm ⁻³ . In this embodiment, the partial pressure of ZnO is 1 × 10 ⁻⁹ Torr as described above.
It can be seen that O can be doped at such a high concentration in spite of its low degree, and thus the doping is easy.

As described above, since the ZnSe epitaxial film 3 according to the present embodiment contains O as a p-type dopant, a p-type ZnSe epitaxial film 3 which has been difficult to obtain conventionally can be obtained.

Although the embodiments of the present invention have been specifically described above, the present invention is not limited to the above-described embodiments, and various modifications based on the technical idea of the present invention are possible.

For example, in the above-described embodiment, the ZnSe epitaxial film 3 is grown by the MBE method. However, as this growth method, a metal organic chemical vapor deposition (MOCVD) method can be used. In addition, O ₂ can be used as a raw material for supplying O. Furthermore, it goes without saying that a p-type GaAs substrate can be used instead of the n-type GaAs substrate 2 used in the above embodiment, and for example, a Ge substrate can also be used.

〔The invention's effect〕

According to the present invention, since oxygen is contained as a dopant, the acceptor level is shallow, so that the SA defect is less likely to occur because the doping amount can be reduced, and this oxygen hardly moves in the crystal, Moreover, doping can be easily performed. This gives p
A type of zinc selenide can be easily obtained.

[Brief description of the drawings]

FIG. 1 is a cross-sectional view for explaining a method of growing a p-type ZnSe epitaxial film according to one embodiment of the present invention, and FIG.
FIG. 3 is a graph showing an example of a photoluminescence spectrum of an O-doped ZnSe epitaxial film grown by the method shown in FIG. 3; FIG. 3 is a graph showing an example of a photoluminescence spectrum of an N-doped ZnSe epitaxial film;
The figure is a graph showing the result of measuring the distribution profile of O in the O-doped ZnSe epitaxial film grown by the method shown in FIG. 1 by SIMS. Explanation of main symbols in the drawings 1: MBE device, 2: GaAs substrate, 3: ZnSe epitaxial film, C ₁
~ C ₃ : Knudsencel.

Continuation of the front page (56) References Preprints of the 35th Symposium on Applied Physics and Related Sciences, Spring, 1988, pp. 237, 29p-Q-10

Claims (1)

(57) [Claims] 1. A method for growing zinc selenide, comprising growing zinc selenide containing oxygen as a dopant by a molecular beam epitaxy method, wherein a molecular beam of ZnO is used as an oxygen source and the partial pressure thereof is substantially reduced. 1 × 1
A method for growing zinc selenide, characterized in that the pressure is set to 0 ^-9 Torr.