JPH1135398A - Compound semiconductor single crystal - Google Patents

Abstract

PROBLEM TO BE SOLVED: To obtain the subject single crystal appropriately used as a substrate for epitaxial growth in the manufacture of a green light emitting device that causes no reduction in luminance by adjusting the concn. of Si and O, both of which exist as impurities in the substrate for epitaxial growth, to values within specified ranges respectively. SOLUTION: In this compound semiconductor single crystal used as a substrate for epitaxial growth, the concn. of Si and O, both of which exist as impurities in the substrate, are adjusted so as to meet the relational expressions, (Si concn.) <1×10<17> atoms/cm<3> and (O concn.) <7×10<16> atoms/cm<3> , respectively. A liquid phase epitaxial growth equipment 2 is provided with a quartz reaction tube 4 in which a boat 6 for epitaxial growth is placed. The boat 6 is provided on its inside with: a substrate holder 8 for setting several, for example five GaP substrates W1 to W5 on it in the longitudinal direction; suveral, several, for example, five growth solution reservoirs 10a to 10e placed in front of the substrate holder 8 so as to correspond to the GaP substrates W1 to W5 , respectively; and also, a solution receiving boat 12.

Description

DETAILED DESCRIPTION OF THE INVENTION

[0001]

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a compound semiconductor single crystal, particularly a GaP single crystal, which is suitably used as an epitaxial substrate for a green light-emitting device without a decrease in luminance.

[0002]

2. Description of the Related Art The demand for higher luminance in a GaP green light emitting diode is increasing year by year, but it is not easy to achieve high luminance because the luminance is reduced by various factors. For example, in a process of manufacturing an epitaxial wafer for a green light-emitting device by performing liquid phase epitaxial growth on a GaP single crystal substrate, there has been a problem that a specific position of the substrate has low brightness.

[0003]

The present inventor examined the impurity concentration of a GaP single crystal substrate having a low luminance and a GaP single crystal substrate having no luminance decrease, and found that the luminance and a specific impurity concentration were constant. It has been found that a relationship exists and the present invention has been completed.

An object of the present invention is to provide a compound semiconductor single crystal, particularly a GaP single crystal, which is suitably used as an epitaxial substrate for a green light emitting device without a decrease in luminance.

[0005]

In order to solve the above-mentioned problems, a compound semiconductor single crystal of the present invention is a compound semiconductor single crystal used as an epitaxial substrate, wherein impurities contained in the substrate are: Si concentration less than 1 × 10 ¹⁷ atoms / cm ³ and O concentration 7 × 10 ¹⁶ atoms
The relationship of less than s / cm ³ is satisfied.

If the concentration is out of the above range, S
Precipitation of iO _{2 and the} like has occurred, and in the epitaxial growth step, defects are increased and luminance is reduced.

The compound semiconductor single crystal is a GaP single crystal.

The compound semiconductor single crystal of the present invention is suitably used for producing a green light emitting device.

[0009]

Embodiments of the present invention will be described below.

FIG. 2 shows a liquid phase growth apparatus used in Experimental Example 1 described below. In the figure, reference numeral 2 denotes a liquid phase growth apparatus having a reaction tube 4 made of quartz. A growth boat 6 is arranged in the reaction tube 4. The growth boat 6 includes a substrate holder 8 for setting a plurality of, for example, five GaP substrates W1 to W5 in a longitudinal direction, and a plurality of growth solution reservoirs 10a to 10e provided corresponding to the respective substrates W1 to W5. And a solution storage boat 12 provided on the front of the substrate holder 8 and slidable with respect to the substrate holder 8.

At a position slightly away from the growth boat 6,
For example, a dopant evaporation source 14 made of Zn is provided. A gas supply port 16 for supplying gas is provided at one end of the reaction tube 4, and a gas outlet 18 for discharging gas is provided at the other end.

Reference numerals 20a and 20b denote heaters provided outside the reaction tube 4. 21 is a drawbar.

EXPERIMENTAL EXAMPLE 1 Using 14 kinds of GaP single crystal substrates shown in Table 1 having different silicon concentrations and oxygen concentrations manufactured by the LEC method and using a liquid phase growth apparatus 2 shown in FIG. The liquid phase epitaxial layer was grown by the procedure, and a green epitaxial wafer was manufactured.

[0014]

[Table 1]

Procedure for Growing Liquid Phase Epitaxial Layer The temperature is raised to 1000 ° C. in an H ₂ atmosphere to dissolve the GaP polycrystal in the Ga melt into the Ga melt. Operate the pull rod 21 to obtain the Ga melts 10a to 10e.
And the substrates W1 to W5.

Next, the temperature is raised to 1010 ° C., and a part of the substrate is melted in a Ga melt to perform a melt back. While cooling the device at a rate of 1 to 3 ° C. per minute,
Grow the layer.

Subsequently, cooling is continued while supplying ammonia gas together with H ₂ gas from the gas supply pipe 16 to grow an n-layer to which N is added. Finally, the dopant evaporation source 14 is heated, and cooling is continued while supplying the Zn vapor together with the H ₂ gas to grow the p-type layer.

When the growth is finished, the Ga melt is separated from the substrate by manipulating 21 to complete the growth.

Next, p is added to this epitaxial wafer.
An Au alloy was vapor-deposited as a mold electrode, and an Au alloy was vapor-deposited as an n-type electrode, and a 0.3 mm square pellet was manufactured to produce a green light emitting diode, and its luminance was measured.

Under the condition of no epoxy coating on the TO-18 header, a good luminance of 4.5 mcd or more was obtained at I _f = 10 mA and a good luminance of 4.5 mcd or more was obtained, and the relationship between the luminance and the impurity concentration was graphed. This is shown in FIG. In FIG. 1, Δ indicates that there was no SiO ₂ deposition and the luminance was 4.5 mcd or more, and X indicates that SiO ₂ deposition was likely to occur locally,
Therefore, those having poor crystallinity and a luminance of less than 4.5 mcd are shown.

From the results shown in FIG. 1, the condition of the impurity concentration suitable for the epitaxial substrate of the green light emitting diode without a decrease in luminance is that the Si concentration is 1 × 10 ¹⁷ atoms / cm ³ or less or the Si concentration is 1 × 10 ¹⁷ atoms / cm ³ or less. When the concentration was 1 × 10 ¹⁷ atoms / cm ³ or more, it was found that the O concentration was 7 × 10 ¹⁶ atoms / cm ³ or less. That is, in order for the green light emitting diode to have a suitable luminance, it is sufficient that the Si concentration is 1 × 10 ¹⁷ atoms / cm ³ or less and / or the O concentration is 7 × 10 ¹⁶ atoms / cm ³ or less.

In the present invention, in particular, the Si concentration is set to 1 × 1
Less than 0 ¹⁷ atoms / cm ³ and O concentration of 7 × 10 ¹⁶ atoms / cm ³
Specifically, a green light-emitting diode having a suitable luminance is obtained.

[0023]

As described above, the compound semiconductor single crystal of the present invention, in particular, the GaP single crystal has an effect that it can be suitably used as an epitaxial substrate of a green light-emitting device without luminance reduction.

[Brief description of the drawings]

FIG. 1 is a graph showing the relationship between Si concentration and O concentration and luminance in Experimental Example 1.

FIG. 2 is a schematic side view illustrating a liquid phase growth apparatus used in Experimental Example 1.

[Explanation of symbols]

2: liquid phase growth apparatus, 4: reaction tube, 6: growth boat,
8: substrate holder, 10a to 10e: growth solution reservoir, 1
2: solution storage boat, 14: dopant evaporation source, 16:
Gas supply ports, W1 to W5: substrate.

Claims (3)

[Claims] 1. Used as an epitaxial substrate
Compound semiconductor single crystal containing impurities contained in the substrate
About 1 × 10¹⁷atoms / cm ^ThreeLess than and
O concentration is 7 × 10¹⁶atoms / cm^ThreeMeet less than
A compound semiconductor single crystal, characterized in that: 2. The compound semiconductor single crystal according to claim 1, wherein said compound semiconductor is GaP. 3. The method according to claim 1, wherein the compound semiconductor single crystal is used for manufacturing a green light emitting device.
The compound semiconductor single crystal according to the above.