CN100419976C - Method for preparing P type ZnO ohmic electrode - Google Patents
Method for preparing P type ZnO ohmic electrode Download PDFInfo
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- CN100419976C CN100419976C CNB2005100165109A CN200510016510A CN100419976C CN 100419976 C CN100419976 C CN 100419976C CN B2005100165109 A CNB2005100165109 A CN B2005100165109A CN 200510016510 A CN200510016510 A CN 200510016510A CN 100419976 C CN100419976 C CN 100419976C
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Abstract
The present invention belongs to the technical field of semiconductor material, which relates to a method for preparing a P-shaped ZnO ohmic electrode. By utilizing an evaporating apparatus, metal Ni is carried out with vapor deposition on P-shaped ZnO to form a first layer of Ni electrode material, and metal Au is carried out with vapor deposition to form a second layer of Au electrode material as an electrode; the prepared electrode carries out rapid thermal anneal in nitrogen with low temperature. Because Ni and Au both have large work functions and alloy can be made from Ni with metal Au, etc., in the process of rapid thermal anneal, atoms between the metal Ni and the metal Au and a thin layer at the surfaces of the metal and the p-shaped ZnO semiconductor material are diffused mutually so as to reduce the barrier height of the metal and a semiconductor interface to achieve the goal of ohmic contact. Because the adhesive capacity of Ni with semiconductor is batter than Au, and Ni can reduce the shrinking ball effect of the metal and the semiconductor when contacting, particularly the ohm characteristics of the electrode can be improved greatly after the rapid thermal anneal; in addition, the chemical stability of Au is good, an Au film formed by vacuum evaporation on the Ni can effectively avoid the degradation of electrode characteristics caused by the electrode material direct contacting external environment to enhance the stability and the service life of the electrode.
Description
Technical field
The invention belongs to technical field of semiconductor, relate to and utilize Ni, Au material and vacuum evaporation and thermal annealing technology prepare the method for P type ZnO Ohmic electrode.
Background technology
From the discovery first of ZnO room temperature ultraviolet stimulated emission in 1997, zno-based semi-conducting material and device become the focus in the current international advanced subject.Making opto-electronic devices such as ultraviolet semiconductor laser and light-emitting diode is one of most important practical application of ZnO.But because ZnO is the n type usually under unadulterated situation, be difficult to prepare P type sample, become a big obstacle of ZnO opto-electronic device preparation.These semiconductor photoelectronic devices all need through the electrode transmission current simultaneously, the dissipation of good electrode contact can the reduction operating voltage and power, and bad electrode contact but can cause device performance to degenerate, and finally causes component failure.Therefore the quality of electrode preparation is directly connected to characteristics such as the electricity of device and optics.Comparatively speaking, the preparation of n type ZnO Ohm contact electrode is easier to, but because the work function of p type ZnO is very big, is difficult to find suitable single electrode material.Therefore prepare the another difficult point that good p type Ohm contact electrode becomes the device preparation.At present, the achievement in research of the p type ZnO Ohmic electrode of report preparation is few in the world, and great majority adopt is the material of noble metal such as Au as p type ZnO Ohm contact electrode, but exist shortcomings such as adhesive ability difference with material for precious metal materials such as Au as the Ohmic electrode of semi-conducting material, have a strong impact on the performance and the stability of device.Secondly, the current-voltage relation curve that provides in the report shows that the voltage that is applied on the ohmic contact is lower, if metal and semi-conductive potential barrier are very high, it is hard to tell the ohm property of prescribed electrode from current-voltage curve.
Summary of the invention
The purpose of this invention is to provide a kind of preparation good reproducibility, the method for the p type ZnO Ohmic electrode of superior performance.Utilize vacuum evaporation Ni and Au, and adopt low temperature rapid thermal annealing technology, effectively utilize the interaction processability between the metal and between metal and the semiconductor stable, the Ohmic electrode that contact performance is good.
For realizing above-mentioned target, the present invention uses vacuum evaporation technique and rapid thermal annealing technology.Utilize vacuum evaporation apparatus evaporation metal Ni on p type ZnO earlier, form ground floor Ni electrode material.Evaporation metal Au forms second layer Au electrode material as electrode then.Next with the electrode low temperature in nitrogen for preparing, as carrying out rapid thermal annealing below 500 ℃.Because the work function of Ni and Au is all bigger, Ni can form alloy with metal such as Au again.In rapid thermal annealing, between metal Ni and the Au and the atom counterdiffusion mutually in metal and the p type ZnO semiconductor material surface thin layer, reduced the barrier height of metal and interface, reach the purpose of ohmic contact.
To understand the present invention in order knowing, the preparation process of p type ZnO Ohmic electrode to be described in detail in detail.
At first to carry out clean to p type ZnO slice, thin piece.Carry out ultrasonic cleaning with acetone, absolute ethyl alcohol respectively, scavenging period is 5～10 minutes, and with behind the deionized water rinsing, with dry N
2Dry up,, reach the purpose that improves the electrodes ability to remove surface impurity.
The electrode pattern of required form and spacing is produced on metal or other material mask plate by mechanical processing technique or other physico-chemical process, and the mask plate area is than big several times at least of ZnO slice, thin piece areas.Mask plate has a front surface, and a rear surface is arranged.P type ZnO slice, thin piece is just placed facing to the figure of the rear surface of mask plate, the back side of ZnO slice, thin piece is sticked to the non-graphics field at the mask plate back side with adhesive tape, together put into then on the specimen holder of vacuum evaporation chamber of vacuum evaporating coating machine, the front surface of mask plate is placed towards evaporation source downwards, and the distance between mask plate and the evaporation source is between 10～15cm.Being 99.99% Ni and Au with purity is placed on respectively in separately the evaporation source tungsten boat as the evaporation material.By mechanical pump and diffusion pump the vacuum of vacuum chamber is extracted into 6.6 * 10
-3Below the Pa, at first evaporate Ni, treat to evaporate Au again after the Ni evaporation, Ni and Au film thickness are generally in several micron dimensions.
The electrode slice, thin piece that evaporation is good took off from mask plate after vacuum evaporation finished, and removed the adhesive tape at the ZnO slice, thin piece back side, put into annealing furnace at nitrogen (N
2) be lower than 500 ℃ in the atmosphere and carry out thermal annealing fast.The rapid thermal annealing time was generally 150 seconds.
The present invention utilizes Ni and Au duplicature, the shortcoming of adhesive ability difference in the time of can reducing greatly to adopt individual layer Au film, avoid " ball contracts " phenomenon, simultaneously because Ni is easy and other metal forms alloy, can promote the counterdiffusion between metal and the semiconductor, the potential barrier that reduces metal and interface is had very big effect.Top Au film can play the purpose of guard electrode again, has avoided the influence of external environment to electrode characteristic.The rapid thermal annealing temperature that adopts is lower, avoided the change of semiconductor material structures and physicochemical characteristics under the high temperature, and I-E characteristic obviously improves, and resistance obviously reduces.These are significant for the good p type ZnO Ohmic electrode of preparation.Thereby lay a good foundation for opto-electronic devices such as preparation and application zno-based ultraviolet semiconductor laser and light-emitting diodes, also the preparation for other semiconductor material with wide forbidden band and device Ohmic electrode provides reference.
Advantages such as adopting vacuum evaporation technique and rapid thermal annealing process combined to prepare Ohmic electrode, to have equipment simple, and operation is simple, and operating cost is cheap.Carry out the low temperature rapid thermal annealing after adopting the vacuum evaporation electrode, can promote the phase counterdiffusion between metal and the semi-conducting material, improve electrode material and semiconductor adhesive ability, thereby effectively reduce the resistance between them, reach the further purpose of improving ohmic contact characteristic.
Adopt Ni and Au double-level-metal film as electrode material, on the one hand because Ni has many advantages when contacting with semiconductor, it is better than Au with semi-conductive adhesive ability, " ball contracts " effect when simultaneously Ni can reduce metal and contacts with semiconductor, interfacial reaction can also be promoted, the ohm property of electrode can be improved after especially annealed greatly; On the other hand because the chemical stability of Au is better, evaporation Au film can effectively avoid electrode material directly to contact with external environment and the electrode characteristic degeneration that causes on Ni, reaches the stability of raising electrode and the purpose in life-span.
Description of drawings
Fig. 1 is current-voltage (I-V) relation curve according to the Ohmic electrode of the experiment condition of example 1 of the present invention preparation, wherein in " ■ " representative instance 1 at N
2In the experiment value of 150 seconds sample of 200 ℃ of following rapid thermal annealings,
In the representative instance 1 at N
2In the experiment value of 150 seconds sample of 300 ℃ of following rapid thermal annealings.
Fig. 2 is current-voltage (I-V) relation curve according to the Ohmic electrode of the experiment condition of example 2 of the present invention preparation, wherein in " ▲ " representative instance 2 at N
2In the experiment value of 150 seconds sample of 300 ℃ of following rapid thermal annealings, in " ● " representative instance 2 at N
2In the experiment value of 150 seconds sample of 400 ℃ of following rapid thermal annealings.
Embodiment
Embodiment 1, and on the p of high resistant type ZnO, behind evaporation Ni and the Au, at 200 ℃, 300 ℃, rapid thermal annealing is 150 seconds in the nitrogen.
Selection of experiment conditions:
P type ZnO slice, thin piece is to adopt molecular beam epitaxy (MBE) method to be grown in sapphire (Al
2O
3) go up the high resistant p type ZnO that nitrogen mixes, area is about 1cm
2, its resistivity is about 60 Ω cm.
At first p type ZnO slice, thin piece is carried out clean: adopt acetone and absolute ethyl alcohol ultrasonic cleaning 5 minutes respectively; With using dry N behind the deionized water rinsing
2Dry up.Employing thickness is 0.2mm, and area is 6 * 6cm
2Tantalum piece is as metal mask plate, and two areas of formation are 1mm on the tantalum piece by being machined in
2Circular aperture is as the shape of electrode, and two electrode spacings are 2mm, and the distance between mask plate and the evaporation source is 12cm, and Ni and Au purity are 99.99%.By mechanical pump and diffusion pump the vacuum of vacuum chamber is extracted into 5.85 * 10
-3Pa.At first evaporate Ni, thickness is about 1 μ m, evaporates Au again, and thickness also is about 1 μ m.Evaporation finishes back taking-up slice, thin piece and puts into annealing furnace respectively at 200 ℃, and 300 ℃, N
2In carry out rapid thermal annealing, the time is 150 seconds, the measurement of current-voltage (I-V) relation is carried out in the darkroom.
Utilize the present invention, on the p of high resistant type ZnO, by evaporation Ni and Au, pass through at 200 ℃ 300 ℃, thermal annealing, find from current-voltage (I-V) characteristic curve, bigger test voltage scope (greater than ± 10V), the linearity of curve is all fine, compare with the sample without annealing, ohmic contact characteristic obtains very big improvement.
Embodiment 2, and on the p of low-resistance type ZnO, behind evaporation Ni and the Au, at 300 ℃, rapid thermal annealing is 150 seconds in 400 ℃ of nitrogen.
P type ZnO slice, thin piece is to adopt molecular beam epitaxy (MBE) method to be grown in sapphire (Al
2O
3) go up the low-resistance p type ZnO that nitrogen mixes, area is about 1cm
2, its resistivity is about 4 Ω cm.
At first p type ZnO slice, thin piece is carried out clean: adopt acetone and absolute ethyl alcohol ultrasonic cleaning 5 minutes respectively; With using dry N behind the deionized water rinsing
2Dry up.Employing thickness is 0.2mm, and area is 6 * 6cm
2Tantalum piece is as metal mask plate, and two areas of formation are 1mm on the tantalum piece by being machined in
2Circular aperture as the shape of electrode, two electrode spacings are 2mm, the distance between mask plate and the evaporation source is 12cm.Ni and Au purity are 99.99%.Vacuum degree is 5.85 * 10 during vacuum evaporation
-3Pa at first evaporates Ni, and thickness is 1 μ m, evaporates Au again, and thickness also is 1 μ m.Evaporation finishes the back and takes out slice, thin piece, puts into annealing furnace respectively at 300 ℃, and 400 ℃, N
2In carry out rapid thermal annealing, the time is 150 seconds.The measurement of current-voltage (I-V) relation is carried out in the darkroom.
Utilize the present invention, on the p of low-resistance type ZnO, by evaporation Ni and Au, process is at 300 ℃, and 400 ℃ of thermal annealings, current-voltage characteristic curve also prove and obtained good Ohm contact electrode.
Claims (5)
1. a method for preparing P type ZnO Ohmic electrode comprises and utilizes vacuum evaporation apparatus evaporation metal Ni on p type ZnO earlier, and form ground floor Ni electrode material, evaporation metal Au forms second layer Au electrode material then, forms Ni and Au duplicature; Next the electrode with preparation carries out rapid thermal annealing under the low temperature in nitrogen, it is characterized in that:
(a) with acetone, absolute ethyl alcohol p type ZnO slice, thin piece is carried out ultrasonic cleaning respectively, scavenging period is 5～10 minutes, with using dry N behind the deionized water rinsing
2Dry up;
(b) make the electrode mask plate, p type ZnO slice, thin piece is fixed on the mask plate;
(c) utilize vacuum evaporation apparatus being lower than 6.6 * 10
-3Evaporation Ni under the condition of Pa, the purity of Ni is at least 99.99%;
(d) evaporation Au on Ni, the purity of Au is at least 99.99%;
(e) in nitrogen atmosphere, temperature is lower than 500 ℃ and carries out thermal annealing fast, and the thermal annealing time is 150 seconds.
2. the method for preparing P type ZnO Ohmic electrode according to claim 1, it is characterized in that the electrode pattern of required form and spacing is produced on metal or other material as mask plate by mechanical processing technique or other physico-chemical process, the mask plate area is than big several times at least of ZnO slice, thin piece areas, mask plate has a front surface, and a rear surface is arranged; P type ZnO slice, thin piece is just placed facing to the figure of the rear surface of mask plate, the back side of ZnO slice, thin piece is sticked to the non-graphics field at the mask plate back side with adhesive tape, together put into then on the specimen holder of vacuum evaporation chamber of vacuum evaporating coating machine, the front surface that makes mask plate is placed towards evaporation source downwards, and the distance between mask plate and the evaporation source is between 10～15cm: Ni and Au are placed on respectively in separately the evaporation source tungsten boat as the evaporation material; By mechanical pump and diffusion pump the vacuum of vacuum chamber is extracted into 6.6 * 10
-3Below the Pa, at first evaporate Ni, treat to evaporate Au again after the Ni evaporation, Ni and Au film thickness are in several micron dimensions; The electrode slice, thin piece that evaporation is good took off from mask plate after vacuum evaporation finished, and removed the adhesive tape at the ZnO slice, thin piece back side, put into annealing furnace and carried out thermal annealing fast.
3. the method for preparing P type ZnO Ohmic electrode according to claim 2 is characterized in that p type ZnO slice, thin piece is low-resistance or highly resistant material.
4. the method for preparing P type ZnO Ohmic electrode according to claim 3 is characterized in that p type ZnO sheet is to adopt molecular beam epitaxy (MBE) method to be grown in the high resistant p type ZnO that nitrogen mixes on the sapphire, and area is 1cm
2, its resistivity is 60 Ω cm; Use acetone and absolute ethyl alcohol to p type ZnO slice, thin piece ultrasonic cleaning 5 minutes respectively; Employing thickness is 0.2mm, and area is 6 * 6cm
2Tantalum piece is as metal mask plate, and two areas of formation are 1mm on the tantalum piece by being machined in
2Circular aperture is as the shape of electrode, and two electrode spacings are 2mm, and the distance between mask plate and the evaporation source is 12cm; By mechanical pump and diffusion pump the vacuum of vacuum chamber is extracted into 5.85 * 10
-3Pa; The thickness of evaporation Ni is 1 μ m, and the thickness that evaporates Au more also is 1 μ m; Evaporation finishes back taking-up slice, thin piece and puts into annealing furnace respectively at 200 ℃, and 300 ℃ are carried out rapid thermal annealing.
5. the method for preparing P type ZnO Ohmic electrode according to claim 3 is characterized in that p type ZnO sheet is to adopt molecular beam epitaxy (MBE) method to be grown in the low-resistance p type ZnO that nitrogen mixes on the sapphire, and area is 1cm
2, its resistivity is 4 Ω cm; With acetone and absolute ethyl alcohol p type ZnO slice, thin piece was carried out ultrasonic cleaning 5 minutes respectively; Employing thickness is 0.2mm, and area is 6 * 6cm
2Tantalum piece is as metal mask plate, and two areas of formation are 1mm on the tantalum piece by being machined in
2Circular aperture as the shape of electrode, two electrode spacings are 2mm, the distance between mask plate and the evaporation source is 12cm; Vacuum degree is 5.85 * 10 during vacuum evaporation
-3Pa, the thickness of evaporation Ni is 1 μ m, the thickness that evaporates Au more also is 1 μ m; Evaporation finishes the back and takes out slice, thin piece, puts into annealing furnace respectively at 300 ℃, and 400 ℃ are carried out rapid thermal annealing.
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| Application Number | Priority Date | Filing Date | Title |
|---|---|---|---|
| CNB2005100165109A CN100419976C (en) | 2005-01-05 | 2005-01-05 | Method for preparing P type ZnO ohmic electrode |
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| CNB2005100165109A CN100419976C (en) | 2005-01-05 | 2005-01-05 | Method for preparing P type ZnO ohmic electrode |
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| CN100419976C true CN100419976C (en) | 2008-09-17 |
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| EP3595019B1 (en) * | 2018-03-30 | 2024-02-28 | Ibaraki University | Photodiode and light-sensitive device |
| CN108922701A (en) * | 2018-05-23 | 2018-11-30 | 江苏时瑞电子科技有限公司 | A kind of thermistor two-layer electrode and preparation method thereof |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001044503A (en) * | 1999-08-04 | 2001-02-16 | Showa Denko Kk | Algainp light emitting diode |
| WO2004020686A2 (en) * | 2002-08-28 | 2004-03-11 | Moxtronics, Inc. | A hybrid beam deposition system and methods for fabricating zno films, p-type zno films, and zno-based ii-vi compound semiconductor devices |
| CN1508847A (en) * | 2002-12-20 | 2004-06-30 | 上海北大蓝光科技有限公司 | Method for preparing low-resistance p-type GaN based material by ohmic contact |
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- 2005-01-05 CN CNB2005100165109A patent/CN100419976C/en not_active Expired - Fee Related
Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| JP2001044503A (en) * | 1999-08-04 | 2001-02-16 | Showa Denko Kk | Algainp light emitting diode |
| WO2004020686A2 (en) * | 2002-08-28 | 2004-03-11 | Moxtronics, Inc. | A hybrid beam deposition system and methods for fabricating zno films, p-type zno films, and zno-based ii-vi compound semiconductor devices |
| CN1508847A (en) * | 2002-12-20 | 2004-06-30 | 上海北大蓝光科技有限公司 | Method for preparing low-resistance p-type GaN based material by ohmic contact |
Non-Patent Citations (1)
| Title |
|---|
| Fabrication of homostructural ZnO p-njunctionsandohmiccontacts to arsenic-doped p-type ZnO. Y.R.Ryu, T.S.Lee.APPLIED PHYSICS LETTERS,Vol.83 No.19. 2003 * |
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