JPS596583A - Znse blue light emitting diode - Google Patents

Abstract

PURPOSE:To enable to form a P-N junction of high perfectibility by epitaxial growth. CONSTITUTION:Using Se 4 as the solvent on e.g. an N type ZnSe substrate 3 in a quartz ampule 1, the impurities of I-a and I-b groups of P type impurities are added into the solvent, source crystal ZnSe 5 is arranged on the high temperature side of the solution wherein temperature is formed, and then the solution reaches equilibrium state, thereafter the N type substrate and the low temperature side of the solution are put into contact each other by errecting the entire body of quartz ampule. Epitaxial growth advances at a constant temperature by the diffusion phenomenon caused by the temperature difference shown on the right side of the figure. Further, to control the pressure of Zn of II group elements, the metal Zn 6 is placed into a Zn chamber through the connected body to the growing chamber with a quartz tube of fine inner diameter and through an equivalent quartz spacer 2, and then the temperature of this chamber is controlled most appropriately. After growth for a required time, the solution is isolated from the substrate, resulting in the completion of the growth, and accordingly the P-N junction is formed.

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a Zn5e semiconductor device, which is expected to emit light on the higher energy side (shorter wavelength side) than green because it has a wider barrier than a light-emitting diode constructed by epitaxial growth. It is a crystal. Among these, ZnS e in particular.

The forbidden voltage of the crystal is 2.67 eV at room temperature, which corresponds to a wavelength of 465 nmK, which is exactly blue.

Therefore, unlike ZnS, which has a wide band gap, Zn5e is a direct transition crystal that can efficiently emit blue light through interband transition without using deep units.

As a result of strenuous efforts made in various places for this purpose, there have been various reports on p-n junctions, but n-type Zn
There is a relatively reliable report that a pn junction is formed by ion implantation of P or As, which becomes a p-type impurity and replaces the lattice position of 5eKSe. However, in this case as well, the forward light emission obtained from the pn junction is dominated by light emission from deep levels, and no light emission from the vicinity of the forbidden band is observed at all.

There are two possible reasons for this. The first is a problem with the crystallinity of the grown crystal. In Zn5e, where the vapor pressure of group Ⅰ elements is higher than that of group Ⅰ elements, Se, a group Ⅰ element, is present in the grown crystals. Since a large number of empty dots are generated and these act as donors, normally only an n-type crystal can be obtained, and a practical p-type crystal cannot be obtained, so that a pn junction has not been formed.

In other words, when a vacancy of a group II element and an impurity combine, they act as a non-luminescent center or form a deep level, so even if p-
Even if an n-junction is formed, the luminous effect is ff! This means that only extremely low levels or those in which light emission is predominant from deep levels can be produced.

The second point is that the important point is under what conditions the impurity that creates a level in the shallow level in the forbidden cloth is added.
1a or G' to be replaced with genus case 1000 points! The nucleus is either an Ib element or a Vb group element substituting at a group (■) lattice point.

For each element, experiments have been conducted to add it by ion implantation or diffusion in hopes of making it p-type, but in each case a deep impurity level is formed. The reason for this is thought to be that a good crystal cannot be grown, so even if impurities are added, a deep level is formed due to a complex of impurities and defects.

In order to eliminate these drawbacks and obtain an efficient blue light emitting diode having an emission peak only near the forbidden area, it is desirable to implant ions into the n-type crystal. However, a p-type epitaxially grown layer of high purity has not been obtained using conventional growth methods.

In order to achieve this objective, the present inventor has already proposed a vapor pressure controlled temperature difference method, and has proposed an epitaxial growth method in which the vapor pressure of Zn is controlled using Se as a solvent in Japanese Patent Application No. 55-78620 and Japanese Patent Application No. 55-78. No. 149693. By using this method, it is possible to form a highly perfect pn junction by epitaxial growth, similar to the IV compound. This specific growth procedure is shown in FIG.

For example, n-type Zn5e is placed in a quartz ampoule l as shown in Figure 1.
A p-type impurity I is deposited on the substrate 3 using Se4 as a solvent.
A and Ib group impurities are added to the solvent to form a temperature difference. A source crystal, ZnS'e5, is placed on the high temperature side of the solution, and after the solution reaches equilibrium, the entire quartz ampoule is turned vertically and placed on an n-type substrate. and the cold side of the solution. Epitaxial growth progresses at the Kazuhiro temperature due to a diffusion phenomenon caused by the temperature i1+%' shown on the right side of FIG.

Furthermore, in order to control Zn7E, which is a Wataru group element, metal Zn6 was introduced into the Zn chamber through a quartz Nupesa 2, which is equivalent to a quartz tube with a narrow inner diameter, and the temperature of this chamber was Optimally controlled.

After growth for a required period of time, the solution and substrate are separated to complete the growth and form a pn junction.

Conversely, it is of course possible to manufacture a pn junction by using a p-type substrate and forming a Kn-type layer thereon.

When epitaxial growth allows the growth of p-type layers on flexible Kn-type substrates and n-type layers on p-type substrates, the question of optimal device structure naturally arises.

The present invention focuses on crystal mobility to provide an optimal device structure. Generally reported Zn5e
The p-type and n-type mobilities of the platform crystal are as follows.

Mobility (crn2/■・5ee) ZnSe n (electron) 600 p (hole) 40 The point that must be noted is that when comparing the mobility, the p-type layer is much smaller than the viscosity, and is several tens of cm2/V.・S
The problem is that the extremely small value of ee (
Ru.

What this fist (1) means is: Insigni: hole diffusion coefficient, μ: mobility.
Assuming that the respective diffusion coefficients at room temperature are between a (cm2/V* s e c) D (c
In2/5ee)20 0.5
2100 2.6, and if we estimate the carrier life τ to the maximum and set it as lμ5 (io-' seconds), the diffusion distance is L = □ and μ = 20ffi, and ■・8ec−・1L table 0.72pfn
10(Lσ1VIIsec e1*L:1.6
Since it is 0 μfi, the thickness of the p-type layer is 10 to 2
A thickness of 4.0 .mu.m is sufficient, and a thickness of 5 .mu.m should also be satisfactory; if the thickness is made thicker than this, the p-type layer merely acts as a series resistance.

Therefore, when manufacturing a diode with low series resistance by forming a Zn5e p-n junction by epitaxial growth, it is preferable to use an n-type crystal as the substrate and grow a thin p-type layer thereon. The thickness of the p-type layer is
The thickness is preferably 5 to 20 μm, particularly preferably around 10 μm.

In light emitting diodes manufactured by growing a p-type epitaxial growth layer using an n-type Zn5e substrate, a remarkable difference in IV characteristics was found depending on the thickness of the p-type' layer, and the impurity density of the p-type layer was 1013 ~ As shown in FIG. 2, it was measured that when the thickness was about 10"7 cm", the series resistance increased when the thickness was 10 .mu.m or more.

With the above structure, high efficiency blue Zn5e can be produced.
A light emitting diode is obtained and is considered to be of high bQtl of industrial value.

Description of the Drawings Figure 1 shows the quartz amble and temperature distribution used in the present invention, and Figure 2 shows the p of the manufactured Zn5e blue light emitting diode.
This is the relationship between the thickness of the shaped layer and the voltage-current characteristics.

1...Quartz ampule, 2--Quartz Nupesa, 3--
-jl type Zn5e substrate, 4 fist**36, 5 se+
+zISe Sorme 1i9k, 6...eznO patent applicant

Claims (1)

[Claims] A thin p-type layer is formed by epitaxial growth on a low-resistance n-type crystal.
Zn5e color #5 characterized by the formation of a shape layer
Shining iode.