JPH04215422A - Liquid epitaxial growth of inp semiconductor - Google Patents

Abstract

PURPOSE:To make In1-xGaxAsyP1-y crystals suitable for manufacture of a light emitting diode whose lattice constant matches an InP substrate within 0.1% and which have a band gap wavelength of 1.3-1.5mum and a thickness of more than 0.5mum epitaxially grow stably on the InP substrate. CONSTITUTION:It is preferable that phosphorus vapor developed from an InP/ In1-zSnz (Zn>=0.4) solution is brought to a substrate surface until an InP substrate is contacted with a material solution at a growth temperature of 650-700 deg.C and until this substrate is contacted again with this solution at a cooling temperature of 0.09+ or -0.01 deg.C per min, preferably, under the temperature control over a range of + or -0.1 deg.C.

Description

[Detailed description of the invention]

0001

BACKGROUND OF THE INVENTION 1. Field of the Invention The present invention relates to a method for liquid phase epitaxial growth of InP-based semiconductors used for manufacturing light emitting devices, light receiving devices, etc.

0002

2. Description of the Related Art FIG. 2 is a cross-sectional view of a surface-emitting type light emitting diode. InP type cladding layer 4, p type In1-i Ga
i Asj P1-j It has a structure in which four types of crystal layers of the contact layer 5 are sequentially formed. A current confinement insulating film 6 is formed on the surface of the p-type contact layer 5.
Furthermore, a p-side electrode 7 is formed. Further, a donut-shaped n-side electrode 8 is formed on the opposite surface of the n-type InP substrate 1, and a condensing ball lens 9 is formed on the surface of the n-type InP substrate 1 at the center of the donut-shaped electrode 8 using silicone resin or the like. fixed, allowing light to be focused into an optical fiber.

The crystal composition of the active layer is adjusted so that the bandgap wavelength of the crystal matches the intended emission wavelength of the light emitting diode and is lattice matched with the InP substrate. At this time, the emission wavelength of light emitting diodes often used in the optical communication field is 1.3 μm or 1.5 μm.
There are m etc. In addition, the design of the thickness of the active layer varies depending on the desired characteristics of the light emitting diode, but the thickness is 0.1 μm.
They range from as thin as 2 μm to as thick as 2 μm. The growth temperature is usually below 650°C, but for example, for an active layer with an emission wavelength of 1.3 μm, the growth temperature is 650°C or less.
It is often carried out in a temperature range of 30 to 640°C, and low-temperature growth of 600°C or less is often adopted for crystal growth of the active layer in the 1.5 μm emission wavelength band. The reason for lowering the growth temperature with a 1.5 μm active layer is as follows.
An InP cladding layer is grown on the 1.5 μm active layer, but during the cladding layer growth, there is a risk that the previously grown active layer will be redissolved in the cladding layer growth solution and the crystals will be destroyed. , in order to prevent this.

The temperature profile of liquid phase epitaxial growth is often determined based on the growth temperature of the active layer. In order to dissolve the growth solution sufficiently and uniformly, the temperature is maintained at a temperature higher than the crystal growth temperature for a certain period of time, and then the growth solution and the substrate crystal are cooled at a predetermined cooling rate until the growth temperature is reached. This temperature profile is typically ±0.2
This is achieved with temperature controllability on the order of degrees Celsius. The cooling rate is often faster than 0.1°C/min (for example, Japanese Patent Publication No. 17797/1983).

Another problem is that in the process of sufficiently dissolving the crystal components in the growth solution immediately before crystal growth, phosphorus is removed from the surface of the InP substrate exposed to atmospheric gas, degrading the substrate crystal. , Methods to prevent this deterioration include: 1) Covering with another InP wafer, 2) Flowing phosphine gas (PH3) together with atmospheric gas,
There are methods such as (2) bringing phosphorus vapor generated from an InP/Sn solution onto an InP substrate.

On the other hand, In1-x Gax Asy P1
-y According to theoretical calculations using crystal thermodynamics, it has been reported that it is difficult to grow homogeneous crystals over a wide range of composition (e.g., Proccedings
of the 1980 International
Symposium on GaAs and Re
latedCompounds, pp115-124
, or Jpn. J. App. Phys. Vol.
．． 21, No. 6 (1982), ppl, 323-3
25). FIG. 3 is a diagram showing an unstable region of crystal growth determined from theoretical calculations of thermodynamics. In the figure, 10 is a line indicating the crystal composition conditions for lattice matching with the InP substrate,
Line segment PQ 11 indicates a region where crystal growth is unstable at a growth temperature of 700°C among the crystal composition regions that lattice match with the InP substrate, and in this region, homogeneous crystals cannot be grown. It was believed that they could not grow. According to this theoretical calculation, the band gap wavelength at room temperature is 1.3 to 1.5 μ by liquid phase epitaxial growth.
In1-x Gax Asy P1- in the range of m
To grow y homogeneously on an InP substrate, the growth temperature is 7.
It was believed that it was necessary to raise the temperature to over 00°C. On the other hand, contrary to theoretical calculations, crystal growth is generally performed at temperatures lower than 650°C, and even if devices such as light emitting diodes are manufactured using semiconductors grown under such conditions, the electrical The properties or optical properties are said to be normal.

[0007] Therefore, the temperature of 650 to 700°C is
Theoretical calculations show that this is a temperature range in which only heterogeneous crystals can grow, and this temperature range has not been utilized because it is on the higher side than conventionally commonly used temperatures.

According to experiments conducted by the present inventors, when an In1-x Gax Asy P1-y crystal lattice-matched to an InP substrate is grown to a thickness of 0.5 μm or more at a growth temperature of 630 to 640°C, For a crystal composition in which the bandgap wavelength is 1.3 to 1.5 μm,
It has been found that a phenomenon in which the half-width of photoluminescence (PL) spectrum becomes abnormally wide appears, making it difficult to stably obtain good crystals. This growth instability is largely attributable to the controllability of the growth temperature, and ±
It becomes noticeable at about 0.2°C. That is, it is lattice matched to the InP substrate, and the bandgap wavelength at room temperature is 1.3~
This becomes noticeable when a crystal with a composition of 1.5 μm is grown to a thickness of 0.5 μm or more. Even with the same crystal growth, if the thickness is thinner than 0.5 μm, there is almost no problem, and it has been confirmed that the half-width of the PL spectrum becomes normal.

Therefore, the present invention provides a material whose lattice constant matches that of the InP substrate at room temperature within 0.1%, and whose bandgap wavelength at room temperature of the active layer is 1.3 to 1.5.
The present invention aims to provide a method for growing wafers having a thickness of 0.5 μm or more and suitable for manufacturing light emitting diodes with a high yield.

0010

[Means for Solving the Problems] The present invention provides an InP substrate with a lattice constant matching within 0.1% with an InP substrate and a bandgap wavelength in the range of 1.3 to 1.5 μm at room temperature. In a method for liquid phase epitaxial growth of an In1-x Gax Asy P1-y crystal having a thickness of 0.5 μm or more on an InP substrate, the raw material solution and the InP substrate are brought into contact in a growth range of 650 to 700°C. , and a method for liquid phase epitaxial growth of an InP-based semiconductor, characterized in that cooling is performed at a cooling rate of 0.09±0.01° C. per minute.

[0011] Note that it is preferable to bring the raw material solution into contact with the InP substrate while controlling the temperature within ±0.1°C, and until the InP substrate is brought into contact with the raw material solution, InP/In1-zSnz ( Z≧0.4) It is preferred to provide phosphorus vapor generated from the solution.

0012

[Operation] The present inventors have discovered that the lattice constant is In at room temperature.
In1-x that matches the P substrate within 0.1%, has a bandgap wavelength in the range of 1.3 to 1.5 μm, and has a thickness of 0.5 μm or more.
In order to liquid-phase epitaxially grow a Gax Asy P1-y crystal on an InP substrate, crystal growth was performed by varying the growth temperature. Moreover, it has been found that by cooling at a cooling rate of 0.09±0.01° C. per minute, liquid phase epitaxial growth of InP-based semiconductors can be performed with good yield. That is, 70
If the growth temperature exceeds 0° C., the wafer is exposed to high temperature after the growth is completed, and deteriorates, making it impossible to stably obtain a good wafer. Further, at a growth temperature lower than 650° C., crystal growth with a thickness of 0.5 μm or more could not be stably performed.

Furthermore, by controlling the temperature of the raw material solution within ±0.1° C. with respect to the temperature profile, it has become possible to further stabilize the crystal growth described above.

Furthermore, in order to dissolve the growth solution sufficiently uniformly, it is necessary to maintain the solution at a high temperature for a certain period of time, but in order to make the solution temperature higher than the conventional solution temperature, phosphorus escapes from the InP substrate surface and heat is generated. Since the possibility of deterioration increases, it is preferable to bring phosphorus vapor generated from the InP/In1-zSnz (Z≧0.4) solution onto the surface of the InP substrate until the InP substrate comes into contact with the raw material solution. The conventional method of preventing thermal deterioration, in which phosphine gas (PH3) is flowed together with atmospheric gas, is not appropriate from a safety perspective because phosphine gas is highly toxic, and the method of covering the substrate with another InP wafer is As a result of experiments, it was confirmed that this method is not effective for growing an active layer at a temperature of 650° C. or higher. On the other hand, thermal deterioration can be prevented by using a solution in which the Sn solvent is saturated with InP.

However, the bandgap at room temperature is
In1-x Gax Asy of 1.3-1.5 μm
In order to grow P1-y crystals stably with good yield at a growth temperature of 650 to 700°C, it is not limited to an InP-saturated Sn solution, but a solvent of In1-zSnz (Z≧0.4) is used to saturate InP. It is sufficient to use a solution prepared by That is, Z<
In the 0.4 solution, phosphorus was observed to escape from the InP substrate surface, causing deterioration. However, for the solutions with Z≧0.4, no deterioration was observed at all.

[0016]

[Example] Each layer constituting a surface emitting diode is made of In
The growth was performed by a method (two-layer solution method) in which the substrate was brought into contact with a saturated solution for growth containing an excessive amount of a P-based crystal component. As the growth apparatus, a horizontal boat-type growth apparatus shown in FIG. 4 was used. The solution composition of each layer was determined by the liquidus line determined from thermodynamics. The growth temperature of the active layer is 660℃ and 660℃.
The temperature was set at 30°C, and the cooling rate during growth was 0.09°C.
The growth temperature was controlled within a range of ±0.1°C. In both cases, the InP/In0.1Sn0.9 solution is used to inject InP until the InP substrate is brought into contact with the raw material solution.
Phosphorus vapor was supplied to the surface of the P substrate.

As a result, a 350 μm thick S-doped I
A 7 μm thick Sn-doped InP cladding layer and a 1.5 μm thick Zn-doped InGaAsP cladding layer on the nP substrate.
Active layer (bandgap wavelength 1.35 μm), thickness 1
A 1 μm thick Zn-doped InP cladding layer and a 1 μm thick Zn-doped InGaAsP contact layer (bandgap wavelength 1.15 μm) could be successively formed. Surface-emitting light emitting diodes were fabricated using these two types of wafers, and the spectral half-width of the diode was measured. Similar to the measurement results of the photoluminescence spectral half-width in Figure 1, the diode fabricated from the 630°C wafer has a half-width of 4 compared to a diode at 660°C.
Only a wide range of about 0% was obtained.

[0018]

[Effects of the Invention] By adopting the above structure, the present invention has a lattice constant that matches an InP substrate within 0.1% at room temperature, and a band gap wavelength of 1.3 to 1.5.
0.5μm
In1-x Gax Asy P1 having a thickness of
-y crystal can be stably grown on an InP substrate by liquid phase epitaxial growth, and it has become possible to easily produce high quality and highly reliable light emitting devices and light receiving devices.

[0019]

[Brief explanation of the drawing]

[Figure 1] I at two different growth temperatures (630°C and 660°C)
2 is a graph showing measured values of the spectral half-width of an InGaAsP crystal grown to be lattice-matched to an nP substrate and to have a thickness of 0.5 μm or more.

FIG. 2 is a diagram showing a cross-sectional structure of a surface-emitting type light emitting diode.

FIG. 3 is a diagram showing an unstable region of crystal growth obtained from theoretical calculations of thermodynamics.

FIG. 4 is a conceptual diagram of a horizontal boat type liquid phase epitaxial growth apparatus used in Examples.

Claims (3)

[Claims] Claim 1: At room temperature, the lattice constant is determined to match that of the InP substrate within 0.1%, and the bandgap wavelength is determined to be in the range of 1.3 to 1.5 μm, and 0.5 μm. In1-x G having a thickness of
In a method for liquid phase epitaxial growth of ax Asy P1-y crystals on InP substrates, the raw material solution and InP substrate are brought into contact in a growth temperature range of 650 to 700°C, and cooling is performed at a rate of 0.09±0.01°C per minute. A method for liquid phase epitaxial growth of InP-based semiconductors characterized by rapid cooling. 2. The method for liquid phase epitaxial growth of an InP-based semiconductor according to claim 1, wherein the temperature of the raw material solution is controlled within ±0.1° C. with respect to the temperature profile, and the raw material solution is brought into contact with the InP substrate. 3. InP/In1-zSnz (Z
≧0.4) The method for liquid phase epitaxial growth of an InP-based semiconductor according to claim 1 or 2, characterized in that phosphorus vapor generated from a solution is produced.