Background technology
At present, ZnTe based compound semiconductor monocrystalline is to be expected to the crystal that can be applied in the luminous element of pure green.
Usually, ZnTe based compound semiconductor monocrystalline adopts following vapor growth method preparation mostly: the end in quartz ampoule is provided with raw material ZnTe polycrystalline, heat this polycrystalline, make near its temperature distillation fusing point, the ZnTe monocrystalline is separated out on the substrate that is arranged at the quartz ampoule opposite side.Can obtain the rectangle ZnTe monocrystal chip of the most about 20mm * 20mm by this method.Recently, in order further to improve the characteristics of luminescence of luminous element, just be devoted to improve crystalline electroconductibility, the method for adding impurity such as phosphorus, arsenic in the oriented crystal of its method.
Also can utilize vertical Bridgman (VB) method or vertical temperature gradient slow cooling (VGF) method to carry out the growth of ZnTe based compound semiconductor monocrystalline in addition.VB method or VGF method can be added impurity when crystal growth, therefore have by adding impurity, easily control the advantage of crystalline electroconductibility.In addition, with the liquid level of sealing agent covering raw material molten solution, this can prevent to sneak into the problem that hinders crystal formation because of impurity by fused solution top, also can suppress the temperature fluctuation in the fused solution simultaneously slightly.
But, by in the ZnTe based compound semiconductor crystal growth of vapor growth method, be difficult to add the impurity of wishing midway, thereby be difficult to control the resistivity of ZnTe based compound semiconductor monocrystalline in growth.In addition, in the vapor growth method, the ZnTe crystalline speed of growth is slow significantly, therefore is difficult to obtain enough big monocrystalline, and the low shortcoming of productivity is arranged.
And, even make the single crystal growing of ZnTe based compound semiconductor, can make the bigger substrate of about 20mm * 20mm, because productivity is low by vapor growth method, make substrate itself become very expensive, the problem of the obstacle that becomes the element exploitation of using ZnTe based compound semiconductor monocrystalline is arranged.
For above-mentioned reasons, prepare ZnTe based compound semiconductor monocrystalline by vapor growth method, this does not have a practicality as industrial process.
On the other hand, be equipped with ZnTe based compound semiconductor monocrystalline by VB method or VGF legal system, then can be grown to large-scale crystal, but because be cooling under the state that covers with sealing agent, make crystal growth, so the missionary society of the coefficient of thermal expansion of sealing agent and growing crystal often causes taking place crystal disruptive situation.
In addition, same with VB method or VGF method, the LEC method also can be added impurity, therefore has by adding impurity, easily controls the advantage of crystalline electroconductibility, but does not almost meet the example that this method of use grows into large-scale ZnTe based compound semiconductor monocrystalline.
The object of the present invention is to provide: can be with the preparation method of the compound semiconductor single crystal of the large-scale ZnTe based compound semiconductor monocrystalline of the crystal quality of excellence growth or other compound semiconductor single crystal.
Summary of the invention
The present invention is the method that liquid encapsulate Czochralski technique prepares compound semiconductor single crystal of passing through of inventing to achieve these goals: be provided with by band round-ended cylinder shape the 1st crucible with in the inboard of the 1st crucible, be provided with splendid attire raw semiconductor and sealing agent in the raw material molten solution filling part that the 2nd crucible with the communicating aperture of above-mentioned the 1st crucible constitutes in the bottom, heating above-mentioned raw materials filling part, make raw materials melt, with the state that is covered by above-mentioned sealing agent seed crystal is contacted with this raw material molten solution surface, draw this seed crystal on one side, make crystal growth on one side, in the method, the temperature of control heater, make the internal diameter of the diameter of growing crystal and above-mentioned the 2nd crucible roughly the same, the state that one side keeps the surface of growing crystal to be covered by above-mentioned sealing agent, make crystalline growth on one side, finish up to crystal growth.
Therefore can prevent that thus constituent from being evaporated by plane of crystal, can make the thermograde in the sealing agent very little, crystal that can the growth quality excellence.Therefore in addition,, can suppress the temperature fluctuation in the raw material molten solution, resemble the present like this material that is difficult to obtain monocrystalline of ZnTe and also can cultivate by seed crystal by reducing the thermograde in the sealing agent.
Can make the diameter of growing crystal and the 2nd crucible internal diameter roughly the same by the control heater temperature, therefore can easily obtain to wish the monocrystalline of diameter, and need not to be used for the temperature control program etc. of the more complicated of control growing crystalline diameter basically.
The addition of above-mentioned sealing agent is set at and can be accompanied by crystal growth, the space that produces between intussusception growth crystal and above-mentioned the 2nd crucible, the amount on the whole surface of covering growing crystal.That is, regulate addition,, also remain in the upper surface of growing crystal even make the space that produces between sealing agent intussusception growth crystal and the 2nd crucible.Thus, growing crystal positively keeps with the state of sealed dose of covering, so the formation element of growing crystal can not evaporate.
Above-mentioned the 2nd crucible has adopted the crucible of internal diameter with crucible bottom pyramidal structure littler than the internal diameter on crucible top.Thus, because the diameter of the growing crystal that draws is little than the internal diameter of the 2nd crucible corresponding position in the institute, growing crystal can not contact with the crucible wall in addition at growth interface, so can obtain the fine crystal.
The side of preferred above-mentioned the 2nd crucible tilts with respect to the scope of vertical direction with 0.2 ° to 10 °, forms taper.Thus, the spatial volume that produces between growing crystal and the 2nd crucible is smaller, therefore can need not the sealing agent of utmost point volume, and promptly available sealing agent covers all surfaces of growing crystal.
Above-mentioned the 2nd crucible is impregnated in the raw material molten solution that is contained in above-mentioned the 1st crucible with 10mm to 40mm, the diameter that makes above-mentioned communicating aperture be above-mentioned the 2nd crucible internal diameter 1/5 or below.Can effectively suppress the temperature fluctuation in the raw material molten solution in the 2nd crucible thus, the good monocrystalline of therefore can growing.In addition, owing to define connecting path with the 1st crucible,,, impurity can be discharged in the 1st crucible by the 2nd crucible, can prevent that impurity from sneaking in the crystal of growth by lifting the 2nd crucible even impurity etc. are blended in the raw material molten solution in the 2nd crucible.
During impurity such as interpolation doping agent, impurity concentration in impurity concentration in the 1st crucible in the raw material molten solution and the 2nd crucible in the raw material molten solution produces difference, by the connecting hole size of the 2nd crucible is changed in 1/5 or following scope of the 2nd crucible internal diameter, it is poor promptly can to control in the fused solution impurity concentration, makes the impurity concentration in the raw material molten solution in the 2nd crucible keep certain.
By the thermograde in the above-mentioned raw materials fused solution is at least 20 ℃/cm or following, can prevent to produce polycrystalline or twin crystal.And the always sealed dose covering of growing crystal even therefore reduce thermograde, is not worried yet and can be decomposed.
The best mode that carries out an invention
Below, the preferred embodiments of the invention are described with reference to the accompanying drawings.
Fig. 1 is the summary construction diagram of the crystal growing apparatus that uses in embodiment of the present invention, and Fig. 2 is the enlarged view of raw material filling part.
The crystal growing apparatus 100 of the present embodiment is made of following: high pressure vessel 1; Be concentric lagging material 2 and the well heater 3 that is provided with circularly in high pressure vessel inside with high pressure vessel; The turning axle 4 that is provided with perpendicular to the middle body of high pressure vessel 1; Be arranged at the pedestal 13 of the upper end of turning axle 4; Be entrenched in the outer crucible (the 1st crucible) 5 of the band round-ended cylinder shape pBN system on the pedestal; Be arranged at the interior crucible (the 2nd crucible) 6 of the pBN system of outer crucible 5 inboards; Top, the lower end of crucible 6 have the fixedly rotary pulling axle 7 of the seedholder 8 of seed crystal 9 in vertically being located at.
Interior crucible 6 has the communicating aperture 6a that is communicated with outer crucible 5 in the bottom surface, via this communicating aperture, and crucible 6 in raw material molten solution 12 can be moved to by outer crucible 5.Interior crucible 6 is fixed on outer crucible 5 or other anchor clamps by suitable clamper (not shown).
Interior crucible 6 has the bottom internal diameter pyramidal structure littler than top internal diameter, and therefore the diameter of the growing crystal that lifts is also littler than the internal diameter on the 2nd crucible corresponding position, and growing crystal can not contact with the crucible wall beyond growth interface.In addition, the spatial volumetric ratio that produces between growing crystal and the 2nd crucible in the crystal growth is less, has reduced sealing agent and has flowed to this spatial amount, and therefore the side of preferred interior crucible tilts with respect to the scope of vertical with 0.2 °-10 °, forms taper.
Rotary pulling axle 7 drive part (not shown) outer with being arranged at high pressure vessel is connected, and constitutes rotary pulling mechanism.Turning axle 4 drive part (not shown) outer with being arranged at high pressure vessel is connected, and constitutes the crucible rotating mechanism, constitutes the pedestal hoisting appliance simultaneously.The rotation of rotary pulling axle 7 and crucible turning axle 4 and the motion of lifting are independently set separately, are controlled.
Use above-mentioned crystal growing apparatus,, can make from the single crystal rod rotation of seeded growth to lift simultaneously, at its lower end growth high purity monocrystalline by LEC (liquid encapsulation Czochralski) (LEC) method.
Then, as an example of compound semiconductor, use 100 pairs of methods that prepare the ZnTe compound semiconductor single crystal of crystal growing apparatus to be specifically described.
In the present embodiment, the pBN system crucible that uses internal diameter 100mm φ * height 100mm * wall thickness 1mm uses the pBN of the pyramidal structure of internal diameter 54mm φ (bottom d2)~56mm φ (top d3) * height 100mm * wall thickness 1mm to make crucible as interior crucible 6 as outer crucible 5.The lateral inclination angle [theta] of crucible 6 is about 0.57 ° with respect to vertical in this moment.
It is the communicating aperture 6a of 10mm that centre portions in the bottom surface of interior crucible 6 forms diameter (d1).The size of communicating aperture 6a is not limited to 10mm, if for interior crucible 6 internal diameters 1/5 or following.
At first, the tellurium that adds up to the zinc of 1.5kg purity 6N and 6N is packed in outer crucible 5 and the interior crucible as raw material, make mol ratios such as zinc and tellurium are, usefulness 400g sealing agent (B it on
2O
3) 11 coverings, the thickness of sealant layer is 35mm.Interior crucible 6 usefulness clampers are fixed, make by well heater 2 with raw materials melt after, be the state of the degree of depth dipping of the liquid level 20mm of distance raw material molten solution.Be accompanied by crystal growth, raw material molten solution slowly reduces, and the lifting by turning axle 4 drives pedestal 13 (outer crucible 5) is risen, thus the impregnation state of crucible 6 in the control.For example with the state of interior crucible 6 maintenances apart from the degree of depth dipping of the liquid level 10mm-40mm of raw material molten solution.
Then, above-mentioned crucible 5,6 is arranged on the pedestal 13, makes in the high pressure vessel 1 to be full of, be adjusted to the pressure of regulation by rare gas element (for example argon).Press down to live the raw material surface with sealing agent on one side then, use well heater 2 temperature heating with regulation on one side, fused zinc and tellurium directly synthesize it.
Afterwards with fusion the state of raw material keep certain hour, seed crystal 9 is contacted with the surface of raw material molten solution.Here, use the seed crystal of crystalline orientation (100) as seed crystal.In addition, in order to prevent the decomposition of seed crystal 9, with shell (not shown) the covering seed crystal of molybdenum system.
Then, will lift turning axle 7 with the speed of rotation of 1-2rpm rotation on one side, lift with the speed of 2.5mm/h, form the crystalline shoulder on one side.After forming shoulder, continue on one side the crucible turning axle to be rotated with 1-5rpm, lift, form main part with the speed of 2.5mm/h.Therefore this moment, the internal diameter of the diameter of the main part of growing crystal 10 and interior crucible 6 was roughly the same as shown in Figure 2, need not to carry out meticulous diameter by pull rate and crucible or the speed of rotation that lifts axle and controlled, and can easily obtain to wish the crystal of diameter.
In addition, because interior crucible 6 has pyramidal structure, during along with crystal growing and pulling crystal 10, growing crystal 10 can not contact with the crucible wall beyond growth interface.Promptly as shown in Figure 2, produce the space between growing crystal 10 and the interior crucible 6, sealing agent enters this space and covers the growing crystal surface.Can prevent that thus the crystal quality that the wall because of crucible 6 in the growing crystal contact causes from reducing.
In addition, because the space between growing crystal 11 and the interior crucible 6 is little, the amount that the sealing agent 11 on crystal top enters the space is few, and plane of crystal always can keep sealed dose 11 state that covers.Can prevent the evaporation of the formation element of growing crystal 10 thus, make the thermograde in the sealing agent very little, thereby can obtain the growing crystal of excellent quality.
Though the side of crucible is 0.57 ° with respect to the inclination angle [theta] of vertical in the present embodiment, the side is fine at 0.2 °-10 ° with respect to the inclination angle of vertical.
Temperature fluctuation in the interior crucible 6 in the raw material molten solution is about 0.5 ℃, and the temperature fluctuation in the raw material molten solution between interior crucible 6 and the outer crucible 5 is 1-2 ℃, and hence one can see that: by making dual crucible structure, and the temperature fluctuation in can suppressing in the crucible 6.
And the thermograde in the raw material molten solution during crystal growth is 10 ℃/cm or following, but because the total surface of growing crystal 10 is sealed dose 11 coverings, crystalline therefore can occur and decompose.
As mentioned above, carry out crystal growth, from sealing agent 11, separate growing crystal 10 after the crystal growth, obtain not having fissured ZnTe compound semiconductor crystal by liquid encapsulate Czochralski technique.Gained ZnTe compound semiconductor crystal is the extremely good monocrystalline that can not produce polycrystalline or twin crystal.The crystalline size of growth is diameter 54mm φ * long 60mm, can realize being regarded as originally the maximization of very difficult ZnTe based compound semiconductor monocrystalline.
Abovely the inventor's invention is specified, but the present invention is not limited to the foregoing description according to embodiment.
For example in the above-described embodiment, formed the communicating aperture of a diameter 10mm φ in the bottom surface of interior crucible 6, but the quantity of communicating aperture is not limited to one,, it is believed that the effect that also can obtain to suppress temperature fluctuation etc. even a plurality of communicating apertures are set.
In addition, by in raw material molten solution, adding impurity, can easily control crystalline electroconductibility as doping agent.At this moment, though the impurity concentration in impurity concentration in the outer crucible 5 in the raw material molten solution and the interior crucible 6 in the raw material molten solution produces difference, but by the size of the connecting hole of the 2nd crucible is changed in 1/5 or following scope of the internal diameter of the 2nd crucible, be the poor of impurity concentration in the may command raw material molten solution, impurity concentration keeps constant in the raw material molten solution in making in the crucible 6.
According to the present invention, prepare compound semiconductor single crystal by liquid encapsulate Czochralski technique: at the 1st crucible and the inboard that is arranged at the 1st crucible by band round-ended cylinder shape, be provided with splendid attire raw semiconductor and sealing agent in the raw material molten solution filling part that the 2nd crucible with the communicating aperture of above-mentioned the 1st crucible constitutes in the bottom, heating above-mentioned raw materials filling part makes raw materials melt, seed crystal is contacted with this raw material molten solution surface, lift this seed crystal on one side, make crystal growth on one side, in above-mentioned preparation method, the temperature of control heater, make the internal diameter of the diameter of growing crystal and above-mentioned the 2nd crucible roughly the same, made crystal growth while the surface that keeps growing crystal by the state that above-mentioned sealing agent covers, finish up to crystal growth, need not to carry out complicated diameter control thus, can easily obtain to wish the crystal of diameter, simultaneously can prevent that in crystal growth constituent from being evaporated by plane of crystal, the crystalline effect that generation can the growth quality excellence.
In addition, owing to be dual crucible structure, can suppress to be contained in the temperature fluctuation in the raw material molten solution in the crucible, can prevent that therefore twin crystal or polycrystalline from producing, generation can obtain extremely good crystalline effect.