JPS6037075B2 - GaAsP crystal growth method - Google Patents

Description

DETAILED DESCRIPTION OF THE INVENTION The present invention provides a GaASP crystal containing two high vapor pressure components.
This method is characterized in that crystal growth is performed by simultaneously applying s pressure and p pressure.

The crystal growth used in conventional compound semiconductor light-emitting devices involves differences in the vapor pressure of each constituent element in both melt growth and solution growth, but the growth method takes the difference in vapor pressure into account. No method was used.

For the past few years, B203 and Ba have been added to the melt during GaP melt growth to prevent high vapor pressure elements from flying out.
Liquid coating method that prevents phosphorus evaporation by placing a liquid seal with low specific gravity such as C12 (J. Appl. Ph. 3)
Although it was said that there were some measures to prevent the evaporation of elements with high vapor pressure, such as those used in It cannot be compensated for and some of it scatters through the coating layer. Furthermore, there is a great risk that these film materials will dissolve into the crystal. In this way, in the conventional method, vapor pressure control for high vapor pressure component elements is not performed even in melt growth that requires high temperatures, and even more so in solution growth where growth is performed below the melting point of the crystal. Based on the established theory that the vapor pressure of elements with high vapor pressure decreases due to the small molar content of crystals in the solvent, and furthermore, the stoichiometric composition of the crystals naturally becomes the correct composition during growth. It can be said that no consideration was given to elements with high vapor pressure. On the other hand, advances in crystal growth technology and social demands have created a need to use high-quality, high-purity compound semiconductor crystals to produce long-life, highly reliable semiconductor devices. To achieve this objective, the most important thing technically is the stoichiometric composition (s ichiometry), which the inventor has been researching for a long time. , if a crystal lattice is configured, ○
It can be safely said that the objective is to control defects caused by deviation from a crystal in which a and As are present in the same ratio. That is, it is thought that the biggest and final barrier to producing crystals of the highest quality lies in how the deviation from the stoichiometric composition can be controlled. ○aAs, Ga
Since the current state of compound semiconductors such as p is as described above, vapor pressure control has not been performed at all in ternary or higher mixed crystals, which are expected to be in great demand in the future. This means that the characteristics of mixed crystal devices can be dramatically improved. In particular, the present invention provides that, among mixed crystals that are particularly important as crystals for light-emitting devices, the vapor pressure of two component elements As and P is 1% compared to that of Ga.
The present invention relates to a method for growing Ga carrier P crystals that is more than successful.

Conventional GaAsP light-emitting diodes have generally been formed by a vapor phase growth method in which a source is supplied from the vapor phase, taking advantage of the high vapor pressure properties of As and P.

Therefore, since crystal growth is carried out in a state where the crystal is grown in a gas phase atmosphere, high vapor pressure component elements are dissociated from the crystal, resulting in crystals with a high content of defects that have a large deviation from the stoichiometric composition. I was only getting it. As a result, the luminous efficiency of the obtained light emitting diode was higher than that obtained by liquid phase growth.
Only a very low value was obtained compared to aNAs, Gap, etc.

Accordingly, the present invention provides a highly efficient GaAsP light emitting diode constructed from a defect-free GaAsP layer by controlling the deviation from the stoichiometric composition of the crystal using a vapor pressure controlled temperature difference liquid phase growth method. For the reasons mentioned above, there are very few examples of growth using liquid phase growth, but by effectively controlling the vapor pressure of group V elements, which have a high vapor pressure, P can be grown in the same way as in the case of compound semiconductors. The deviation from the stoichiometric composition was controlled, a GaAsP layer with low defect density was obtained, and a GaAsP semiconductor device with dramatically superior characteristics compared to conventional products obtained by vapor phase growth was constructed. The present invention will be described in detail below with reference to the drawings. Figure 1 is a schematic diagram of a growth boat 1 for conventional liquid-phase epitaxial growth of compound semiconductors, in which a source 3 of the crystal to be grown is placed in a solvent 2 such as Ga or ln, and the growth temperature is gradually cooled and overflowed. This is epitaxial growth on the substrate crystal 4.

In this case, high vapor pressure elements such as As and P during growth
evaporates from inside the board. FIG. 2 shows an embodiment of a crystal growth furnace for epitaxially growing mixed crystal GaAsP containing two elements whose vapor pressure is to be controlled according to the present invention.

The vapor pressure controlled temperature difference method has conventionally been applied to the crystal growth of compound semiconductors such as CaAs and Gap, but when this is applied to the growth of Ga pseudo-P, a mixed crystal, the vapor pressure value applied during crystal growth is The deviation from the stoichiometric composition of the precipitated crystals (i.e. the amount of defects) is controlled, and the composition x of the precipitated crystals is defined by the composition x of the source crystals 13 and 14 suspended at the top of the solution, and is determined by the applied vapor pressure. is characterized in that this value does not change.

In GaAs, -xPx, the value of x changes from GaAs to G
It is possible to realize a mixed crystal having properties of each crystal up to ap.

In the boat 6, there are two melt tanks 21 and 22 for two-layer epitaxial growth, in which the solvents Gall and 12 are placed for 20 minutes, respectively, and the source crystal Ga vessel and NPx are set according to the composition of the crystal to be grown. Corresponding GaAsP polycrystal 13
, 14 and 2 or GaAs and GaP respectively
As. - Pour an equivalent amount into xPx and separate the source crystal part and substrate 9.
The configuration is such that there is a temperature difference 10 of about 20° C. between the two.
Furthermore, as shown in the figure, there is a separate injection point for elements for controlling vapor pressure in the low temperature section, and thin quartz tubes 31 and 32 (inner diameter 3 side).
Place the lids 41 and 42 from above the melt tank so that it is semi-closed.
Insert via. On the low temperature side, put metal ship 30 for 1 night, red phosphorus 40 for 0.5 night, pine 51 which is separate from growth furnace 15,
By changing the temperature of the control furnace 52 for P, the As pressure and the P pressure applied to the growth area were respectively controlled. The epitaxial growth was kept constant at 800 qC, and the applied pressure and P pressure were controlled independently, and the composition corresponding to red light emission (x =
0.3) of Ga$MPo. Using a source crystal having a composition of No. 3, p- or n-type layers having the same composition were successively epitaxially grown to fabricate a light-emitting diode. At this time, the As pressure and P pressure applied during crystal growth were applied independently in the following 16 types of combinations. As pressure is lOTor
r, 50rorr, 100Torr, 500morr,
P pressure is lOTon, 50Ton, 100Torr, 50
0Tom and 4 types each (As pressure, P pressure) (10, 10
), (10, 50) (10, 100)... As a result of producing a light emitting diode by growing two layers of each of the combinations of single-stripe lotuses, the composition of the resulting mixed crystal changes. Since there is no diodes, the emission wavelength from the diode is almost the same, but the emission brightness varies greatly depending on the applied false pressure or P pressure.
Since the number of defects in the crystal can be suppressed to the minimum when Ton is released, a light emitting diode with high brightness can be obtained as a result.

The luminance of the combination (5050) is 7
At 00 and t-L/10 mA, brightness more than twice as high as the other 15 combinations of 1000 to 300 skin-L/10 skin A was obtained. When an X-ray Lang photograph of the crystal grown under these conditions was taken, it was found that the crystal was free of dislocations. When similar growth experiments are conducted at various temperatures, the vapor pressure values obtained for light emitting diodes with the best characteristics at each temperature are different and show values that depend on the growth temperature. FIG. 3 shows this optimum vapor pressure value plotted against the growth temperature. In the figure, the shaded area X between P Skin Shame 1 Cut eXp (-Group V) and Popt=1・93×1PeXp (-Group V) is defect-free with no deviation from the stoichiometric composition. The optimum vapor pressure of P and P to be applied to grow a crystal of P is shown.

Moreover, as long as the composition of OA and Px is between 0<x<1, the optimal As pressure and P pressure values that can obtain a defect-free crystal in any composition are within the shaded area in Figure 3. It was experimentally confirmed that ×. Therefore, it is clear that the CaAsP crystal obtained by the conventional growth method contained an extremely large number of defects because such vapor pressure control was not carried out, and by using this growth method,
In addition to being able to provide extremely high-brightness light emitting diodes, it is also possible to provide high-performance GaAsP semiconductor devices with a wide range of applications, and the contribution to the semiconductor industry is immeasurable.

[Brief explanation of the drawing]

FIG. 1 is a schematic diagram of a conventional liquid-phase epitaxial growth boat, and FIG. 2 is an example of a growth apparatus used in the present invention.
FIG. 3 is an example of the dependence of the optimum value of the pressure applied during growth on the growth temperature. Figure 1 Figure 2 Figure 3

Claims (1)

[Claims] 1 In temperature difference liquid phase epitaxial growth of GaAs_1_-_xP_x (0<x<1), the crystal growth temperature is set to T.
(°K), Boltzmann constant and k, As pressure and P pressure applied during growth are each 1.93×10^6ex
p(-1.01eV/kT)Torr and 4.61×10
The vapor pressure is kept constant between ^6exp (-1.01eV/kT) Torr, and the As pressure and P pressure are simultaneously applied from above the solution to control the deviation from the stoichiometric composition of the GaAs_1_-_xP_x crystal. A GaAsP crystal growth method characterized in that a GaAs_1_-_xP_x layer consisting of at least two epitaxially grown layers is formed on a substrate crystal.