A kind of preparation method of zinc oxide based p type material
Technical field
The invention belongs to semiconductor material growing technical field, be specifically related to a kind of preparation method of zinc oxide based p type material.
Background technology
Wide bandgap semiconductor, because it is having broad application prospects aspect solid-state illumination, short wavelength's semiconductor laser and ultraviolet detector, is known as third generation semiconductor.ZnO is one of representative of wide bandgap semiconductor materials, it is a kind of direct gap semiconductor of mono-symmetry, energy gap under its room temperature is 3.37eV, there is the exciton bind energy up to 60meV, this numerical value is far above the hot ionization energy of room temperature (26meV), can ensure that it at room temperature realizes the stimulated emission of efficient excitonic luminescence and low threshold value.Therefore, ZnO is considered to prepare the especially ideal material of the opto-electronic device such as laser (LD) of short-wave long light-emitting diode (LED).Compared with other wide bandgap semiconductor materials, ZnO also has aboundresources, cost of material is cheap; Environmental friendliness, nontoxic; Film-forming method is simply various, and growth temperature is low; Easily acquisition can be used as the semi-conducting material of substrate and realizes homoepitaxy; With wet corrosion technique compatibility, be beneficial to a series of advantages such as photoelectron is integrated.For these reasons, become international forward position and focus for the research of Zinc oxide based semiconductor photoelectron material.And consider zno-based material may meet country space interplanetary communication etc. concerning a series of significant problems of national defense safety and the national economic development on to the key components such as short wavelength semiconductor laser, UV photodetector Strategic Demand.
At present, the research of ZnO has been obtained to a series of gratifying achievements in research both at home and abroad.On aluminum-magnesium acid scandium substrate continue Japanese scientist in 2004 in low mismatch, obtain after the electroluminescence of ZnO homojunction, 2005, luminescence and broad stopband II-VI family of application National Key Laboratory semiconducter research group are prepared the ZnO homogeneous pn junction LED based on Sapphire Substrate in the world first, and obtain the bluish violet electroluminescence under room temperature, subsequently, domestic and international many seminar have also reported ZnO homogeneous pn junction and the electroluminescence based on quantum well structure in succession.It is worth mentioning that the people such as Ryu are taking BeZnO as building layer, ZnO is LED and the LD that trap layer is prepared quantum well type zno-based, and obtain UV electroluminescence and Laser emission, and we have also obtained the Laser emission of the royal purple wave band that belongs to ZnO under room temperature condition in ZnO/GaN heterostructure, only 0.8mA of its threshold current, this all illustrates that zno-based material can be competent at the needs of the short wavelength light electric device such as ultra-violet light-emitting and low threshold value Ultra-Violet Laser device completely.
But, because the ionization energy of acceptor impurity in ZnO is high, make p-type zno-based material property prepared by conventional method can not meet device requirement.The Method and process that lacks the p-type ZnO material of repeatable high, stable, the low-resistance of preparation, high mobility is still the bottleneck place that obstruction zno-based opto-electronic device is walked out laboratory.
Traditional p-type ZnO material preparation mainly depends on by different technological means mixes respectively or simultaneously material internal by I family and V group element, presents acceptor state to realizing above-mentioned two family's elements in ZnO.But, theoretical and experimental result shows, the acceptor activation that can be applicable to the acceptor impurity of ZnO material can be mostly more than 200meV, and we are not difficult to obtain by the relation of acceptor impurity ionization level and acceptor activation energy, also not enough one thousandth of acceptor's ionization level in ZnO cannot effectively provide hole at all.So people have to ensure have abundant acceptor to improve the concentration in hole in material by low-temperature epitaxy and heavily doped method, but, no matter be that reduction growth temperature and excessive impurity mix the deterioration that all can cause material crystalline quality, the inhibitions to hole transport such as aggravation dislocation scattering, neutral impurity scattering and ionized impurity scattering, directly affect hole mobility and other physical characteristic of material, and the stability of severe jamming material property.Also someone,, by being with modulation engineering, expects to reduce acceptor level, makes acceptor impurity be easy to ionization, but not yet obtains applicable effective technology means.Can see, acceptor activation energy height is the main difficulty place of preparation p-type zno-based material.If have a kind of method or technique can make p-type ZnO doping break away from the constraint of high acceptor activation energy, make the generation in hole no longer rely on acceptor " spontaneous ionization ", just can under relatively low impurity doping content, obtain higher hole concentration, improve acceptor impurity validity, reduce the obstruction of defect to hole, realize efficient, stable, p-ZnO repeatably.
Summary of the invention
The object of the invention is the preparation method's poor stability in order to solve existing zinc oxide based p type material, repeatable low problem, and a kind of preparation method of zinc oxide based p type material is provided.
The preparation method who the invention provides a kind of zinc oxide based p type material, the method comprises:
On basal layer, prepare graded bedding;
On described graded bedding, prepare cap rock;
Described basal layer is the Mg of oxygen polar surfaces
xzn
1-xo (0.6>=x>=0.2) material, the thickness of described basal layer is not less than 5nm;
Described graded bedding has the structure of content gradually variational, and its structure is expressed as Mg from bottom to top
xzn
1-xo/Mg
x-δzn
1-(x-δ)o/Mg
x-2 δzn
1-(x-2 δ)o/ ... / Mg
x-(n-1) δzn
1-[x-(n-1) δ]o/Mg
x-n δzn
1-(x-n δ)o (δ → 0, n is natural number; N δ=x; Be abbreviated as graded-MgZnO), described graded bedding thickness is not more than 1 μ m;
The material of described cap rock is ZnO, and the thickness of cap rock is not less than 300nm.
Preferably, the thickness of described basal layer is 20-50nm.
Preferably, the thickness of described graded bedding is 50nm~200nm.
Preferably, the thickness of described cap rock is 1 μ m~3 μ m.
Preferably, described basal layer prepares on substrate.
Principle of the present invention
The invention provides a kind of preparation method of zinc oxide based p type material, the method is by the Mg in oxygen polar surface
xzn
1-xthe graded-MgZnO material layer of growth components gradual change on O material, the piezoelectric polarization that material internal is produced is consistent with spontaneous polarization direction, under the acting in conjunction of two kinds of polarization, the Mg that component is adjacent
y-δzn
1-(y-δ)o/Mg
yzn
1-y(y is arbitrary value between δ to n δ to O, δ → 0) high magnesium component one side can produce charge accumulated, the amount of charge accumulated increases along with the increase of graded-MgZnO material layer thickness, and the electric field forming due to charge accumulated can enable to be with run-off the straight, tilt in order to neutralize the electric charge and the little energy band that are produced by polarization, make system beinthebalancestate, be subject to chief commander to be forced to ionization and produce hole, these holes are the most at last at graded-MgZnO material layer one lateral enrichment and form three-dimensional cavitation layer, and carry out work with charge carrier identity.Method of the present invention is not in the situation that having acceptor impurity to mix, and the field only producing by heterostructure causes hole injection just can realize hole injection; And for the material that has acceptor impurity to mix, as long as polarization charge accumulation is sufficient, most acceptors can ionization, and this ionization can not be subject to the restriction of ionization energy, same due to the not impact of acceptor's ionization energy, its hole concentration temperature influence of p-ZnO sill that utilizes polarization abductive approach to obtain is little, and this makes it have good temperature stability.
Beneficial effect of the present invention
The invention provides a kind of preparation method of zinc oxide based p type material, polarization abductive approach is applied to zno-based wide-band gap material system by the method, carry out the preparation of p-type zno-based material, polarization abductive approach utilizes the electric charge of polarization accumulation and electric field promotion acceptor's ionization, its application makes zno-based material break away from the high restriction of acceptor's ionization energy, compared with " sitting back and waiting " acceptor's " spontaneous ionization " with conventional method, be " making an initiative sally "; The way of inducing by polarization, can greatly improve acceptor's ionization level and the doping efficiency of acceptor impurity, solve a difficult problem for zno-based P-type Doping, method repeatability of the present invention is high, simultaneously due to the not impact of acceptor's ionization energy, the material electric property temperature influence of preparing by the method is little, has good temperature stability.
Brief description of the drawings
Fig. 1 is the structural representation of the zinc oxide based p type material that obtains of preparation method of the present invention.
Fig. 2 be in the zno-based p-type material prepared of the inventive method in graded bedding Mg and Zn component with the relation curve of the variation of graded bedding thickness.
Embodiment
The preparation method who the invention provides a kind of zinc oxide based p type material, as shown in Figure 1, the method comprises:
On basal layer 102, prepare graded bedding 103;
On described graded bedding 103, prepare cap rock 104;
Described basal layer 102 is the Mg of oxygen polar surfaces
xzn
1-xo material, the thickness of described basal layer is not less than 5nm, is preferably 20-50nm, must make himself to have complete structure, and the polarity of follow-up structure is realized and being controlled;
Described graded bedding 103 has content gradually variational structure, and the x (0.6>=x>=0.2) of graded bedding Mg component from basal layer reduces to 0 gradually with varied in thickness, and its structure can be expressed as Mg from bottom to top
xzn
1-xo/Mg
x-δzn
1-(x-δ)o/Mg
x-2 δzn
1-(x-2 δ)o/ ... / Mg
x-(n-1) δzn
1-[x-(n-1) δ]o/Mg
x-n δzn
1-(x-n δ)o (ZnO) (δ → 0, n is natural number; N δ=x; Be abbreviated as graded-MgZnO), δ is a certain 0 the numerical value of leveling off between 0-1, to ensure that Mg component changes with a certain Grad continuously from x, can think the gradient of Mg component, graded bedding lower surface Mg component is consistent with basal layer, i.e. Mg
xzn
1-xo (0.6>=x>=0.2), graded bedding upper surface Mg content is 0, i.e. ZnO, described graded bedding thickness is not more than 1 μ m (micron), is preferably 50nm~200nm;
The material of described cap rock 104 is ZnO, the thickness of cap rock is not less than 300nm, and preferable range is 1 μ m~3 μ m, must make himself to have perfect lattice structure, and graded bedding lattice is produced to constraint, make in graded bedding piezoelectric polarization consistent with material spontaneous polarization direction.
Basal layer 102 of the present invention can independently exist, and preferably on substrate 101, prepares.
Basal layer 102 of the present invention, graded bedding 103 and cap rock 104 are oxygen polarity.
The material of graded bedding of the present invention be prepared as prior art, graded bedding of the present invention is not unique, can be other metal except Mg and the alloy of ZnO, as Be yet
xzn
1-xo/Be
x-δzn
1-(x-δ)o/Be
x-2 δzn
1-(x-2 δ)o/ ... / Be
x-(n-1) δzn
1-[x-(n-1) δ]o/Be
x-n δzn
1-(x-n δ)o (ZnO) (δ → 0, n is natural number; N δ=x), but choose basal layer and cap rock should match with graded bedding, make the spontaneous polarization in total consistent with piezoelectric polarization direction.Basal layer of the present invention can carry out the doping of known ZnO acceptor impurity, and for example, acceptor impurity can be: the V group elements such as N, P, As, Sb, or the I family element such as Li, Na, K.
Fig. 2 be in the zno-based p-type material prepared of the inventive method in graded bedding Mg and Zn component with the relation curve of the variation of thickness, in figure, transverse axis represents component, the longitudinal axis represents the thickness of counting from substrate surface, X refers to the component of Mg in graded bedding upper surface, what curve 201 represented is the variation of Mg component with thickness, shown in curve 202 is the variation of Zn component with thickness, and curve 201 and curve 202 are to have corresponding relation with the structure on right side.From curve 201, we can see, Mg component reduces to 0 from X gradually with graded bedding thickness, correspondingly, Zn component shown in curve 202 increases with graded bedding thickness and is increased to 1 from (1-X) gradually, notices, this variation tendency is linear change.Like this, basal layer can be realized the lattice constraint to graded bedding lower surface, adjacent Mg in graded bedding
y-δzn
1-(y-δ)o/Mg
yzn
1-ythe piezoelectricity and spontaneous polarization superposition in the same way of O (y is arbitrary value between δ to n δ, δ → 0) interlayer, cap rock fetters graded bedding upper surface.
Below in conjunction with embodiment, the present invention is done to further detailed description.
Embodiment 1
By the specific implementation method of MOCVD preparation polarization induction p-type ZnO material
Zinc source adopts diethyl zinc, magnesium source to adopt the luxuriant magnesium of dimethyl two, oxygen source to adopt oxygen, zinc source, magnesium source splendid attire are in bubbling bottle, by carrier gas (nitrogen), the effective ingredient in bubbling bottle is taken out of, in the present embodiment, the organic source capsule of MOCVD system road is standard pipeline, therefore pass into the amount in source of reaction chamber and the temperature in source and carrier gas flux about (temperature in source is higher, carrier gas flux is larger, and the amount in source that passes into reaction chamber is more).
Step 1, substrate is prepared: the C surface sapphire substrate of oxygen polarity is cleaned, be placed in MOCVD reaction chamber (shown in corresponding diagram 1 101)
Step 2, carries out Mg on Sapphire Substrate surface
xzn
1-xthe growth of O basal layer: zinc source temperature is 0 DEG C, carrier gas flux 10sccm, oxygen flow 60sccm; 70 DEG C, magnesium source, carrier gas flux 20sccm.At the basal layer of graded bedding superficial growth 30nm.Mg
xzn
1-xin O, Mg component is 30%, i.e. Mg
0.3zn
0.7o, is oxygen polarity (shown in corresponding diagram 1 102)
Step 3 is carried out the growth of graded bedding: keeping zinc source temperature is 0 DEG C on basal layer, carrier gas flux 10sccm, and oxygen flow 60sccm, continues to pass into reative cell; Magnesium source is passed into reaction chamber, magnesium source temperature is cooled to 20 DEG C from 70 DEG C with 0.05 DEG C/5s speed simultaneously, carrier gas flux 20sccm, and due to the decline of source temperature, in reaction chamber, magnesium source content reduces gradually, and the content of magnesium in prepared film is reduced gradually.Grow on the basal layer graded bedding of 70nm.(shown in corresponding diagram 1 103)
Step 4 is carried out the growth of ZnO cap rock: keeping zinc source temperature is 0 DEG C, and carrier gas flux is 10sccm, and oxygen flow is 60sccm, stops passing into magnesium source on graded bedding.On graded bedding, deposit the Zn polar surfaces zno-based plinth layer that 1 μ m is thick (shown in corresponding diagram 1 104).
The explanation of above embodiment is just for helping to understand method of the present invention and core concept thereof.It should be pointed out that for those skilled in the art, under the premise without departing from the principles of the invention, can also carry out some improvement and modification to the present invention, these improvement and modification also fall in the protection range of the claims in the present invention.
To the above-mentioned explanation of the disclosed embodiments, make professional and technical personnel in the field can realize or use the present invention.To be apparent for those skilled in the art to the multiple amendment of these embodiment, General Principle as defined herein can, in the situation that not departing from the spirit or scope of the present invention, realize in other embodiments.Therefore, the present invention will can not be restricted to these embodiment shown in this article, but will meet the widest scope consistent with principle disclosed herein and features of novelty.