JPS62209833A - N-type semiconductor crystal - Google Patents

Abstract

PURPOSE:To obtain a crystal which has a low resistivity and emits blue light at a room temperature by making the composition ratio of a group II element in the crystal less than a specific value. CONSTITUTION:In order to realize a blue light emitting device (especially LED and LD), a low resistivity and a high blue light emission intensity are essential. For that purpose, paying attention to a group II element which is an N-type donor impurity contained by ZnSxSe1-x, the relations between the group II element concentration in the crystal, the electron concentration (n), the electron mobility mu, a deep electron trapping level and further a PL spectrum at a room temperature obtained by SIMS analysis are studied. As a result, if the group II impurity concentration is predetermined within a proper range, the growth of the crystal which shows a low resistivity and blue light emission can be made to grow. In other words, the group II impurity concentration contained in ZnSxSe1-x (0<=x<=0.1) is selected to be less than 50ppm, or more preferably, less than 50ppm and not less than 1ppm.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a vapor phase growth method (MOC) using an organometallic compound.
The present invention relates to an N-type semiconductor crystal consisting of a zinc selenide sulfide (Zn5x8e, -x (0≦X≦1) crystal containing Group I elements grown by VD method).

[Technical background of the invention and its problems]

Zn5xSe has high expectations as a blue light emitting element
, -x (0≦X≦1) crystal has a strong self-compensation effect and is extremely difficult to control as an electrically conductive type. Therefore, it is difficult not only to form a PN junction but also to obtain a crystal with low resistivity without appropriate post-treatment. In recent years, MBg and MOCVD, which are said to be crystal growth methods under non-thermal equilibrium,
As the law develops, there are expectations that it will suppress the self-compensation effect. Actually MBE.

With both MOCVD methods, it has become possible to obtain low-resistance N-type semiconductor crystals without post-treatment by adding appropriate impurities.

However, semiconductor crystals with lower resistance (ZnSxSe,

Although the crystal) can emit light (~47.011 m1) due to interband transition at room temperature, which is essential for blue light emitting devices,
Moreover, DA emission with a wide spectrum width involving deep levels appears predominant. Furthermore, the intensity of light emission involving this deep level increases as the amount of impurity added increases. Also, according to Deepleiel evaluation by DLTS, an increase in the deep electron trap concentration is observed as the amount of impurity added increases.

From the above, although it is possible to grow a low-resistance crystal using MBg and MOCVD, there are problems such as the generation of deep levels due to the addition of impurities, which inhibits blue light emission.

[Purpose of the invention]

In view of the above circumstances, the present invention defines an appropriate range of n-type impurity concentration contained in a crystal aimed at realizing a blue light emitting device.

[Summary of the invention]

The gist of the present invention is that Zn5XSe1-X(0
≦X≦0.1), the concentration of group ■ impurities contained in
A more preferable range is 11) so that it is less than m.
It is characterized in that it is set to I) m or more and 50 pI) m or less.

As mentioned above, in order to realize a blue light emitting device (especially an LED or LD), it is essential that the device has low resistance and high blue light emission intensity at room temperature. Therefore, the present inventor proposed Zn5xSe, -X
Focusing on Group I elements, which are n-type donor impurities, contained in the crystal, we analyzed the Group 1 element concentration in the crystal, electron concentration (n), electron mobility -), and deep electron trap level obtained by SIMS analysis. Furthermore, the relationship with the PL spectrum at room temperature was investigated. As a result, it was found that it is possible to grow crystals that have low resistivity and emit blue light by setting the concentration of group (Ⅰ) impurities within an appropriate range. The range is as described above, and in crystals with a concentration higher than this range, the emission in the green to red region involving deep levels becomes stronger, so the emission color does not appear to be blue, and as the concentration increases, it changes from white to white. It becomes visible as orange luminescence.

Furthermore, when the concentration is low, the resistivity increases and the relative luminescence intensity is also weak, making it unsuitable for practical use.

Furthermore, in carrying out the present invention, it is particularly important to use MO as a growth method.
CVD method is suitable, especially selenium and sulfur.

When organic compounds are used as both zinc and Xia group impurity raw materials, there are advantages of excellent crystallinity and excellent controllability of impurity concentration.

Furthermore, MIS exploded using the above N-type semiconductor crystal.
The type or PN junction type light emitting device exhibited good blue light emission with a low applied voltage. If the concentration of Group 1 impurities is lower than the above-mentioned range, the applied voltage will be high, making it unsuitable for practical use.

On the other hand, when the concentration is high, there is a problem that the emitted light color shifts to the longer wavelength side.

〔Effect of the invention〕

According to the present invention, Zn8xSeI, which is a blue light emitting element material,
-x(0≦X≦0.1) It has become possible to obtain a crystal that has a low resistivity and emits blue light at room temperature.Furthermore, an MIS type or PN junction type light emitting device using the above crystal can be obtained. When the applied voltage was low, it began to emit blue light.

[Embodiments of the invention]

Embodiments of the present invention will be described below with reference to the drawings.

<Example 1> This will be explained using Zn5e grown on a GaAs substrate as an example.

Dimethyl selenium (DM8e), dimethyl zinc (DMZ)
And triethylaluminum (
Zn5e was grown on a GaAs substrate under the conditions shown in Table 1 using Zn5e (TEAL). The amount of Al added was determined by changing the amount of Thalium supplied.

Table 1 Growth Conditions Figure 1 shows the relationship between carrier concentration (11), electron mobility (11), and resistivity C) determined by the van der Pouw method for the amount of Al added. Figure 2 shows the ratio of the interband emission intensity (IB) of the t-luminescence (PL) spectrum and the emission intensity related to the deep level (Ideep) for the same (aluminum addition amount and 325 f'1 m He-Cd laser light excitation). It shows R(I deep/I n ). Further, FIG. 3 shows the relationship between the electron trap level concentration obtained from the DLT8 spectrum and the amount of Al added.

From FIG. 1, n increases with the amount of Al added, but begins to decrease at a point where n increases. μ decreases with the amount of Al added. This result is AI! When the amount of addition reaches a certain point, the degree of compensation increases rapidly, and it can be considered that the generation of carriers is hindered. This tendency becomes even clearer in FIG. That is, as the Al concentration increases, the number of scattering centers such as ionized impurities increases, resulting in a sharp decrease in μ at low temperatures.

According to FIG. 2, when the Al11 degree is low, I deep is hardly observed. R increases as A69 degrees increases. When A69 degrees exceeds 5099 m, R increases rapidly, and the color does not appear blue, but instead appears white or even orange. This phenomenon corresponds to the fact that IB decreases on the i high concentration side. Furthermore, in areas where the Al degree is lower than 1 pl)m, blue light emission is dominant, but the intensity is very weak.

From FIG. 3, relatively shallow electron traps with a low concentration can be seen when the Al9 degree is low. However, as the A77 degree increases, the concentration of deeper levels increases, and deeper trap levels that were not seen at low concentrations occur.
This concentration increases. The increase in these deeper trap levels is correlated with the behavior of Ideep.

The above results show that simply having a large n and a low ρ does not necessarily result in blue light emission (Deepleve
It is clear that there is a limit to the region where l is small and ρ is low. Therefore, low resistivity and blue light emission can be obtained within the AA' concentration range of 1 to 50 ppm.

The AllQ degree in the Zn5e crystal can be controlled by the amount of 'I'BAl supplied during growth. However, the manner in which 'Al is incorporated into the crystal varies depending on conditions such as temperature, pressure, W/V ratio, combination of raw materials, etc. during growth, and cannot be determined unambiguously. However, even if the crystal is grown under various growth conditions, it is essential that the IJI degree in the grown crystal be within the above-mentioned range.

<Example 2> A MIS type light emitting device will be explained in which ZnSe doped with A/ is grown on a GaAs substrate, 5in2 of about 100A is deposited on this, and a metal electrode is further formed on it. .

FIG. 6 shows intensity changes of blue light emission (In) and long wavelength side light emission (I deep ) in the emission spectrum of the device shown in FIG. 5 with various A69 degrees. Furthermore, the applied voltage and A when the current flows 10mA
Examining the relationship between l concentration, we found that when the concentration is lower than lppm, the applied voltage increases suddenly, and when the concentration is high, I de
EP is increasing. Therefore, also when forming a light emitting element, it can be said that the group II concentration is appropriate in the range of 1 to 50 ppm.

[Other embodiments of the invention] Note that the present invention is not limited to the above embodiments.

By using Zn8x8e, lattice matching with the substrate can be achieved, resulting in a crystal layer of even better quality. The group impurity is not limited to kl, and Ga, In, etc. can also be used. Furthermore, it is possible to grow the raw materials in various combinations of Zn, S, Se, and any of the Zhen group raw materials. The growth conditions can also be changed in various ways, such as temperature, pressure, and supply amount.
The group impurity concentration may be within the range of the present invention. Furthermore, if the present invention is applied to the N layer of a PN junction type light emitting element, not only the MIS type, a more reliable and purer blue light emitting element can be obtained.

In addition, various modifications can be made without departing from the gist of the present invention.

[Brief explanation of drawings]

Figure 1 shows Al in Zn5e obtained from SIMs analysis.
A diagram showing the relationship between a and n, and rice and ρ. Figure 2 is a diagram showing the relationship between Al concentration in Zn5e and PL intensity ratio obtained from SIMS analysis. Figure 3 is a diagram showing the relationship between a and n and PL intensity ratio. Zn
Figure 4 shows the temperature change in Hall mobility, and Figure 5 shows the composition of the MIS type light emitting device obtained by the present invention. The figure shown in FIG. 6 is a diagram showing the relationship between A49 degrees in Zn5e obtained from SIMS analysis and emission intensity. 51 51-41 electrode, 52... Zn5e: kl crystal, S3... GaAs substrate, 54... Ohmic electrode.

Claims (2)

[Claims] (1) Zinc selenide sulfide (ZnSxS) containing group III elements grown by a vapor phase growth method using an organometallic compound
In the N-type semiconductor crystal consisting of e_1_−_x {0≦x≦0.1), the composition of the group III element in the crystal is 1.
An N-type semiconductor crystal characterized by having a concentration of ppm or more and 50 ppm or less. (2) The semiconductor crystal according to item 1 of the patent description, characterized in that the crystal is grown using organic compounds as raw materials for selenium, sulfur, zinc, and Group III elements.