JPS584833B2 - Method for manufacturing G↓aA↓s light emitting diode - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention relates to a method of manufacturing a GaAs light emitting diode.

In the conventional manufacturing method of high-power light emitting diodes using GaAs crystal, Ga
Ga containing Si, an amphoteric impurity, in As crystal
Using a melt (Ga solvent containing GaAs or As), n-type GaAs crystals and p-type GaAs crystals are continuously grown by a liquid phase epitaxial method.

The external quantum efficiency of a GaAs light emitting diode manufactured in this manner, in which both the n-layer dopant and the p-layer dopant are Si, is usually as high as 3 to 4%.

However, the rise time of light emission from this Si-doped GaAs light emitting diode varies depending on its current density;
It's not fast at all.

For example, the rise time of light emission is approximately 2.0 μsec at a current density of 6 A/cm 2 and approximately 0.5 μsec at 60 A/cm 2 .

The method of manufacturing a GaAs light emitting diode of the present invention provides a light emitting diode with high output and fast rise time.

The method for manufacturing a GaAs light emitting diode according to the present invention will be explained in detail below with reference to the drawings.

FIG. 1 shows an example of a crystal growth apparatus used in manufacturing the GaAs light emitting diode of the present invention.

In the figure, 10 is a boat for crystal growth.

11 is a substrate holder, and an n-type GaAs crystal substrate 1 is placed in a groove 12 of this substrate holder 11.

On the other hand, 13 is a melt holder, a melt reservoir 14 contains a Ga melt containing Si (Ga solvent containing GaAs or As) 16, and a melt reservoir 15 contains a p
A Ga melt (containing GaAs or As in a Ga solvent) 17 containing a form impurity such as Zn is prepared.

The crystal growth board 10 prepared as described above is pushed into the soaking section 22 of the quartz tube 21.

After the entire crystal growth board 10 has settled down to a constant temperature,
A Ga melt 16 is brought into contact with the surface of the GaAs crystal substrate 1 to lower its temperature.

As the temperature decreases, Si is deposited on the surface of the GaAs crystal substrate 1.
A doped n-type GaAs crystal layer 2 is grown (FIG. 2a).

(At this time, care must be taken to ensure that the conductivity type of the Si-doped GaAs crystal deposited on the surface of the GaAs crystal substrate 1 is n-type by setting the crystal growth temperature range sufficiently high.

) At the stage when the Si-doped n-type GaAs crystal layer 2 has grown to an appropriate thickness, the Ga melt 16 is
s Remove from above the crystal layer 2.

Next, a Ga melt 17 is brought into contact with the surface of the Si-doped n-type GaAs crystal layer 2.

The temperature of the soaking section 22 of the quartz tube is kept constant and this state is maintained.

During this period, the Zn contained in the Ga melt 17 was Si-doped.
Zn-doped p-type GaAs diffuses into the crystal layer 2.
An s-diffusion layer 3 is formed (FIG. 2b).

After maintaining this state until the depth of diffusion reaches an appropriate value, the temperature is lowered and a Zn-doped p-type GaAs crystal layer 4 is formed on the Zn-doped p-type GaAs diffusion layer 3 to finish the growth ( Figure 2C).

Surface of n-type GaAs crystal substrate 1 and p-type GaAs crystal layer 4
Electrodes 6 and 7 are formed on the surface, respectively, to complete the production of the GaAs light emitting diode 8 (FIG. 2d).

FIG. 3 shows the vicinity of the pn junction of the GaAs light emitting diode 8.

Each number in FIG. 3 corresponds to that in FIG. 2.

GaAs light emitting diode 80 light emitting region is Zn doped p
This is a part of the Zn-doped p-type GaAs diffusion layer 3 and the Zn-doped p-type GaAs growth layer 4, that is, a portion in contact with the Zn-doped p-type GaAs diffusion layer 3.

In Fig. 3, when a current is applied to the light emitting diode, some of the electrons injected from the Si-doped n-type GaAs crystal layer 2 are radiatively recombined in the Zn-doped p-type GaAs diffusion layer 3, and the rest pass through this layer and are transferred to the Zn The light reaches the doped n-type GaAs growth layer 4K and undergoes radiative recombination there.

Generally, in a light emitting diode that generates light in the p layer by electron injection, the internal quantum efficiency of the p layer depends on the carrier concentration of the p layer, and the higher the carrier concentration, the higher the internal quantum efficiency.

However, if the carrier concentration in the n layer is increased, the electron p
The injection efficiency into the layer will be poor, and the external light efficiency of the light emitting diode will not be large.

Therefore, if you increase the carrier concentration in the p-layer and at the same time increase the carrier concentration in the n-layer, the leakage current of the diode increases due to the increase in crystal defects and the effects of the impurities themselves, making it impossible to increase the external quantum efficiency. .

In FIG. 3, the p layer adjacent to the p-n junction 5 is made of Si.
This is a Zn diffusion layer 3 of a doped GaAs crystal growth layer.

The Si-doped GaAs epitaxial layer has very good crystallinity and has few non-radiative recombination centers.

The electrons injected from the Si-doped GaAs growth layer 2
Part of the radiative recombination occurs in the Zn diffusion layer 3 of the i-doped QaAs growth layer, but the rest passes through this layer and the Zn-doped p-type Ga
The light reaches the As growth layer 4, where radiative recombination and non-radiative recombination occur.

The carrier concentration of the p-type GaAs diffusion layer 3 is Zn-doped p
Since the carrier concentration is lower than the carrier concentration of the Zn-doped p-type GaAs growth layer 4, the injection efficiency of electrons into the p-layer becomes better than when the Zn-doped p-type GaAs growth layer 4 is in direct contact with the p-n junction.

Therefore, by controlling the Zn doping amount of the p-type diffusion layer 3 and the p-type growth layer 4 and the thickness of the p-type GaAs diffusion layer 3, a GaAs light emitting diode with high external quantum efficiency can be manufactured.

On the other hand, the rise time of light emission also depends on the Zn doping amount of the p-type diffusion layer 3 and the p-type growth layer 4 and the thickness of the p-type GaAs diffusion layer 3.

If the p-type GaAs diffusion layer 3 is made thinner, the rise time of light emission can be made faster, but if it is made too thin, the external quantum efficiency becomes extremely small.

In fact, using the manufacturing method of the present invention, we have been able to improve the external quantum efficiency by controlling the Zn doping amount and the thickness of the p-type GaAs diffusion layer (both the n-layer dopant and the p-layer dopant are Si). The external quantum efficiency is approximately the same as that of a GaAs light emitting diode, and the rise time of light emission is approximately 20
A GaAs light emitting diode with a current density of 60/cm 2 could be obtained.

In the above description, crystal growth was performed by a tipping method, but the method for manufacturing a GaAs light emitting diode of the present invention can also be applied to other liquid phase crystal growth methods, such as a taping method or a temperature difference method.

In addition to Zn, the acceptor impurities doped into the second Ga melt include Cd, Ge, Hg, Li, and N.
Of course, a, Mg, etc. may also be used.

[BRIEF DESCRIPTION OF THE DRAWINGS] FIG. 1 shows an example of a crystal growth apparatus used in the method of manufacturing a GaAs light emitting diode of the present invention, FIG. 2 is a diagram illustrating an example of the manufacturing process, and FIG. The figure is the second
This figure shows the vicinity of the pn junction of the GaAs light emitting diode shown in Figure d. In the figure, 1: n-type GaAs crystal substrate, 2: Si-doped n-type GaAs crystal layer, 3: p-type GaAs diffusion layer, 4: Zn-doped p-type GaAs growth layer, 5: p-n junction.

Claims (1)

[Claims] 1 A first Ga containing Si on an n-type GaAs crystal substrate.
A step of forming an acceptor in a Si-doped n-type GaAs crystal using a melt (GaAs or As dissolved in a Ga solvent); A second Ga melt containing impurities (GaAs in the Ga solvent)
By keeping this state in contact for a certain period of time, impurities that serve as acceptors contained in the second Ga melt are removed from the Si-doped n-type G.
The Si doped n is internally diffused into the aAs crystal growth layer.
forming a p-n junction in the GaAs crystal growth layer;
After the step, the second Ga melt is used to form the n-type G.
A method for manufacturing a CaAs light emitting diode, comprising a step of performing liquid phase growth of a p-type GaAs crystal on an aAs crystal growth layer.