CN104022220B - GaN Gunn diode based on AlGaN/GaN superlattice electron emission layer and manufacturing method - Google Patents

Abstract

The invention discloses a GaN Gunn diode based on an AlGaN/GaN superlattice electron emission layer and a manufacturing method of the GaN Gunn diode. The GaN Gunn diode and the manufacturing method mainly aim at solving the problems that an existing Gunn device is low in power and poor in heat dissipation performance. The diode comprises a main part and an auxiliary part. The main part comprises a SiC substrate, an AlN nucleating layer, an n+GaN cathode ohmic contact layer, the electron emission layer, an n-GaN active layer and an n+GaN anode ohmic contact layer from bottom to top. The auxiliary part comprises an annular electrode, a substrate electrode, a circular electrode, a passivation layer, an open hole and a through hole. An AlGaN/GaN superlattice is adopted for the electron emission layer and has four to six cycles, the thickness of a GaN layer and the thickness of an AlGaN layer in each cycle both range from 10 nm to 20 nm, and an Al component in the AlGaN layer is linearly and gradually changed to 15% from 0% from bottom to top. The length of a dead zone can be remarkably reduced, dislocation concentration is reduced, and the GaN Gunn diode is suitable for terahertz frequency band work.

Description

Based on AlGaN/GaN superlattices electron emission layer GaN Gunn diode and manufacture method

Technical field

The invention belongs to technical field of microelectronic devices, particularly to gunn two pole of wide band gap semiconducter GaN material Pipe, can be used for high frequency, high power device making.

Technical background

Owing to GaN has, energy gap is big, stable chemical nature, disruptive field intensity are high, is difficult to the feature of hot intrinsic, because of This is for the manufacture of millimeter wave large power semiconductor device, and GaN is considered to be the material got a good chance of, and is also current Study hotspot.Compared with tradition Group III-V compound semiconductor GaAs, the negative resistance oscillation fundamental frequency of GaN reaches 750GHz, considerably beyond the 140GHz of GaAs, additionally, for the electronic device of GaN base, its output is also Exceed 1～2 order of magnitude than GaAs base electron device, the most several watts of hundreds of milliwatt can be reached.Therefore, research The millimeter wave high power device of GaN base is significant.

Some n having been proposed that at present⁺/n^-/n⁺The gunn device structure main distinction is at n^—The doped forms of active area, as Uniform Doped active area structure, the insertion non-uniform doping active area structure of groove (notch) doped layer, band N-shaped point The non-uniform doping active area structure of peak doping.But Uniform Doped active area structure and notch doped structure is " dead District " length is relatively big, is not the most obvious for improving the electrical characteristics of device.With the structure of N-shaped spike doping, though The problem so improving " dead band " length, but cannot effectively reduce concentration of dislocations in hetero-epitaxy.

In order to realize while reducing " dead band " length, reduce concentration of dislocations.Document report in recent years proposes The concept of AlGaN electron emission layer, but the most mostly use the structure of monolayer or bilayer.Such as use monolayer AlN or AlGaN, as electron emission layer, makes dislocation bend the effect buried in oblivion although this structure can play, But can only once filter, concentration of dislocations can not be significantly reduced.Also AlGaN/GaN is proposed double-deck Structure, but this structure does not accounts for AlGaN is used gradual change Al component, between GaN and AlGaN There is bigger lattice mismatch, once Stress Release, electron emission layer will introduce new dislocation, affect Terahertz The electrical characteristics of device.

Summary of the invention

It is an object of the invention to provide a kind of GaN Gunn diode based on AlGaN/GaN superlattices electron emission layer And manufacture method, its outstanding feature is both can to have reduced " dead band " length to improve domain stability, again can be right Dislocation reduces lattice mismatch degree to improve device active region crystalline quality while realizing multiple times of filtration.

For achieving the above object, technical scheme is as follows:

One. based on AlGaN/GaN superlattices electron emission layer GaN Gunn diode, including main part and auxiliary body Point, this main part includes from bottom to top: SiC substrate, AlN nucleating layer, n⁺GaN cathode ohmic contact layer, electricity Sub-emission layer, n^-GaN active layer and n⁺GaN anode ohmic contact layer；Auxiliary body portion includes annular electrode, substrate electricity Pole, circular electrode, passivation layer, perforate and through hole；Annular electrode and underlayer electrode, as the negative electrode of device, distinguish position In n⁺The top of GaN cathode ohmic contact layer and the lower section of SiC substrate, circular electrode is positioned at as the anode of device n⁺The top of GaN anode ohmic contact layer, passivation layer is positioned at the top of annular electrode and circular electrode；Perforate and through hole Laying respectively in passivation layer and SiC substrate, annular electrode is connected by through hole with underlayer electrode, forms longitudinal device architecture；

Described electron emission layer uses AlGaN/GaN superlattices, and these superlattices are provided with 4～6 cycles, each cycle In GaN layer thickness be 10-20nm, AlGaN layer thickness is that the Al component in 10-20nm, and AlGaN layer is dense Degree is from bottom to up by 0% linear gradient to 15%.

As preferably, described SiC substrate be 4H-SiC semi-insulating type substrate, 6H-SiC semi-insulating type substrate or 6H-SiC conducting type substrate.

As preferably, the thickness of described AlN nucleating layer is 30～60nm.

As preferably, described n⁺The thickness of GaN cathode ohmic contact layer is 100～400nm, doping content be 1～ 2×10¹⁸cm^-3。

As preferably, described n^-The thickness of GaN active layer is 0.5～2 μm, and doping content is 0.5～2 × 10¹⁷cm^-3。

As preferably, described n⁺The thickness of GaN anode ohmic contact layer is 100～400nm, doping content be 1～ 2×10¹⁸cm^-3。

Two. the method making above-mentioned GaN Gunn diode, comprise the steps:

(1) epitaxial growth AlN nucleating layer:

The method using metal organic chemical vapor deposition MOCVD, on N-shaped or insulated type SiC substrate, outward Epitaxial growth thickness is the AlN nucleating layer of 30～90nm；

(2) epitaxial growth n⁺GaN cathode ohmic contact layer:

On the AlN nucleating layer of extension, by the method for metal organic chemical vapor deposition MOCVD, extension is raw Long doping content is 1～2 × 10¹⁸cm^-3, thickness be 100～400nm n⁺GaN cathode ohmic contact layer；

(3) epitaxial growth electron emission layer:

3.1) at the n of extension⁺On GaN cathode ohmic contact layer, utilize molecular beam epitaxy MBE technology, first extension Growth thickness is that 10-20nm, Al concentration of component is from bottom to up by the AlGaN layer of 0% linear gradient to 15%；Continue Using MBE technology, epitaxial growth thickness is the GaN layer of 10-20nm, and this GaN layer and AlGaN layer constitute super One cycle of lattice；

3.2) repeated growth 3-5 the cycle, electron emission layer is formed.

(4) epitaxial growth n^-GaN active layer:

On AlGaN/GaN superlattices electron emission layer, utilize metal organic chemical vapor deposition MOCVD's Method, epitaxial growth doping content is 0.5～2 × 10¹⁷cm^-3, thickness be the n of 0.5～2 μm^-GaN active layer；

(5) epitaxial growth n⁺GaN anode ohmic contact layer:

At described n^-On GaN active layer, the method utilizing metal organic chemical vapor deposition MOCVD, extension Growth doping content is 1～2 × 10¹⁸cm^-3, thickness be 100～400nm n⁺GaN anode ohmic contact layer；

(6) the big round table surface of etching formation:

Use reactive ion etching technology that the epitaxial layer in SiC substrate is performed etching, be etched to SiC substrate always Upper surface, to form a diameter of d₀Big round table surface, wherein 30 μm < d₀<60μm；

(7) etching formation small circular table top:

Described big round table surface continues use lithographic technique, form a diameter of d₁Small circular table top, etching depth To n⁺GaN cathode ohmic contact layer, 10 μm < d₁<20μm；

(8) circular electrode and annular electrode are formed:

8.1) vacuum electron beam evaporation technique is used, at the n that small circular table top and etching expose⁺GaN cathode ohmic contact Ti/Al/Ni/Au multiple layer metal is deposited on layer,

8.2) use metal lift-off techniques, small circular table top is formed the anode of circular electrode, i.e. Gunn diode, Cathode ohmic contact aspect is formed annular electrode；

(9) formation metal and the Ohmic contact of GaN:

At a temperature of 950 DEG C, it is passed through Ar₂The time of carrying out is the rapid thermal annealing of 50 seconds, makes n⁺GaN is with circular Ohmic contact is formed between electrode metal and annular electrode metal；

(10) etching formation through hole:

Use reactive ion etching technology, form n through hole, n in surface on back side of SiC substrate etching=1, etching depth is extremely Annular electrode；

(11) negative electrode of formation GaN Gunn diode:

At SiC through hole and the surface on back side of SiC substrate deposit Ti/Al/Ni/Au multiple layer metal of etching formation, form anode lining Hearth electrode, underlayer electrode is connected together with electrode with annular and constitutes Gunn diode negative electrode；

(12) epitaxial growth SiN passivation layer expose the anode of diode:

12.1) method of employing PECVD is at the SiN passivation layer that device front deposition thickness is 200～400nm,

12.2) use reactive ion etching technology to form perforate 11 on small circular table top, expose Gunn diode anode.

Present invention have the advantage that

A. due to the fact that have employed Al content gradually variational AlGaN/GaN superlattice structure can play as electron emission layer The effect of thermionic emission.

Owing to the energy gap of AlGaN from GaN is different, therefore under the effect of polarity effect, AlGaN/GaN is different The GaN side of matter knot can form two-dimensional electron gas；Once the electronics in two-dimensional electron gas obtains enough energy, just The constraint of potential well can be shaken off, inject high energy electron to active area, so that device duty enters into negative impedance region, shape Become Gunn oscillation；The gunn device structure obtained based on this layer can significantly decrease " dead band " length, and shortening device has The length of source region, thus improve operating frequency and the conversion efficiency of device.

B. the present invention uses Al content gradually variational AlGaN/GaN superlattice structure as electron emission layer, can play repeatedly Reduce concentration of dislocations, the effect of reduction lattice mismatch.

Due to dislocation, often AlGaN/GaN structure through a cycle will occur first order buckling, bury in oblivion, thus real Repeatedly burying in oblivion of existing dislocation, reaches to significantly reduce the purpose of concentration of dislocations；And present invention employs linear gradient Al Design of components, makes the lattice mismatch between GaN and AlGaN minimize, thus avoids the generation of misfit dislocation, Improve the crystalline quality of GaN material.

C. the GaN Gunn diode of the present invention has longitudinal electrode structure, completely compatible tradition Gunn diode Packaging technology, is very beneficial for the installation of high-frequency resonant intracavity and makes Terahertz oscillation component.

Accompanying drawing explanation

Fig. 1 is the sectional structure chart of GaN base Gunn diode of the present invention；

Fig. 2 is the top view of Fig. 1；

Fig. 3 is the AlGaN/GaN superlattices electronics genetic horizon structure for amplifying schematic diagram in the present invention；

Fig. 4 is the process chart that the present invention makes GaN Gunn diode.

Detailed description of the invention

Seeing figures.1.and.2, the GaN Gunn diode device architecture of the present invention includes main part and auxiliary body portion. Main part is from bottom to top: SiC substrate 1, AlN nucleating layer 2, n⁺GaN cathode ohmic contact layer 3, electronics are sent out Penetrate layer 4, n^-GaN active layer 5 and n⁺GaN anode ohmic contact layer 6；Auxiliary body portion includes: annular electrode 7, Underlayer electrode 8, circular electrode 9, passivation layer 10, perforate 11 and through hole 12.Wherein:

SiC substrate 1 can be that device provides physical support, also can play the effect of heat radiation, in SiC substrate 1 simultaneously Having through hole 12, the number of through hole 12 is n, n >=1, for annular electrode 7 is connected with underlayer electrode 8, shape Become longitudinal device architecture；The thickness of AlN nucleating layer 2 is 30～60nm, can play the effect reducing dislocation density； n⁺The doping content of GaN cathode ohmic contact layer 3 is 1～2 × 10¹⁸cm^-3, thickness is 100～400nm, at this layer It is provided with big round table surface, a diameter of d of table top₀, 30 μm < d₀<60μm；n^-The doping content of GaN transit layer 5 It is 0.5～2 × 10¹⁷cm^-3, thickness is 100～400nm, and the doping content of this layer and thickness will determine Gunn diode Operating frequency and mode of operation；n⁺The doping content of GaN anode ohmic contact layer 6 is 1～2 × 10¹⁸cm^-3, thick Degree is 100～400nm, is provided with small circular table top on this layer, a diameter of d of table top₁, 10 μm < d₁<20μm。 As in figure 2 it is shown, central circular is the anode of diode, the annulus in outside is annular electrode 7, through hole 12 and substrate Electrode 8 does not the most draw.

n⁺The top deposit Ti/Al/Ni/Au multiple layer metal of GaN anode ohmic contact layer 6 forms circular electrode 9, constitutes The anode of device；Annular electrode 7 and underlayer electrode 8 lay respectively at n⁺The top of GaN cathode ohmic contact layer 3 and The lower section of SiC substrate 1, the two is collectively as the negative electrode of device.

Electron emission layer 4 uses AlGaN/GaN superlattices, as it is shown on figure 3, these superlattices have 4～6 cycles, AlGaN layer thickness in each cycle is 10-20nm, and GaN layer thickness is 10-20nm, Al group in AlGaN layer Point concentration is from bottom to up by 0% linear gradient to 15%, to realize the multiple times of filtration to dislocation, makes lattice mismatch Littleization.

With reference to Fig. 4, the manufacture method of GaN Gunn diode of the present invention, provide following three kinds of embodiments:

Embodiment 1: make the GaN Gunn diode of 4H-SiC semi-insulating type substrate.

Step 1, selects the 4H-SiC semi-insulating type substrate of a diameter of 2 inches, carries out thinning to the back side, until lining Base thickness degree is 150 μm.

Step 2, puts into MOCVD reative cell by semi-insulating for 4H-SiC type substrate, sets growth temperature as 600 DEG C, Being passed through trimethyl aluminium and nitrogen in reative cell, under conditions of keeping pressure to be 40Torr, growth thickness is simultaneously The AlN nucleating layer of 30nm.

Step 3, is increased to 1000 DEG C by the substrate that grown AlN nucleating layer, is passed through three in reative cell simultaneously Methyl gallium, nitrogen and N-shaped doped source silane, under conditions of keeping pressure to be 40Torr, growth thickness is 100nm, Doping content is 1.0 × 10¹⁸cm^-3N⁺GaN cathode ohmic contact layer.

Step 4, puts into the sample obtained by said process in MBE reative cell, is passed through three in reative cell simultaneously Methyl gallium, nitrogen and trimethyl aluminium, and first linearly increasing trimethyl aluminium be passed through metering, rear stopping is passed through trimethyl aluminium, Pressure be 400Torr, under conditions of temperature is 1000 DEG C, the AlGaN/GaN in 4 cycles of epitaxial growth is super brilliant Lattice, the AlGaN layer thickness in each cycle is 10nm, and GaN layer thickness is 10nm, Al component in AlGaN layer Concentration, from bottom to up by 0% linear gradient to 15%, forms electron emission layer.

Step 5, puts into the sample growing electron emission layer in MOCVD reative cell, sets air pressure as 40Torr, It is passed through trimethyl gallium, nitrogen and N-shaped doped source silane, under conditions of temperature is 1000 DEG C, epitaxial growth simultaneously Thickness is 0.5 μm, and doping content is 0.5 × 10¹⁷cm^-3N^-GaN active layer.

Step 6, continues to use the mode of MOCVD, is passed through trimethyl gallium, nitrogen and N-shaped doped source silicon simultaneously Alkane, is 40Torr keeping air pressure, and under conditions of temperature is 1000 DEG C, epitaxial growth thickness is 100nm, adulterates dense Degree is 1.0 × 10¹⁸cm^-3N⁺GaN cathode ohmic contact layer, forms GaN epitaxial layer.

Step 7, takes out above-mentioned GaN epitaxial layer from MOCVD reative cell, at GaN epitaxial layer On carry out photoetching, form the big circular mask pattern of a diameter of 30 μm, then use reactive ion etching technology, use BCl₃/Cl₂GaN epitaxial layer is performed etching by gas, till being etched to expose 4H-SiC substrate surface, is formed Big round table surface.

Step 8, carries out photoetching on the big round table surface formed, forms the coaxial small circular table top of a diameter of 10 μm Mask pattern；Use reactive ion etching technology again, use BCl₃/Cl₂Big round table surface is performed etching by gas, etching The degree of depth enters into n⁺200nm in GaN cathode ohmic contact layer, forms small circular table top.

Step 9, evaporates Ti/Al/Ni/Au multiple layer metal with vacuum electron beam evaporation equipment successively at whole device surface, Thickness is respectively 30nm/120nm/50nm/160nm, forms circular electrode and annular electrode through metal-stripping.

Step 10, in argon gas atmosphere, at a temperature of 950 DEG C, carries out the rapid thermal annealing of 50 seconds to whole device Process, form GaN Ohmic contact.

Step 11, carries out photoetching to the device after thermal annealing, forms 4 a diameter of 10 μm at the back side of 4H-SiC substrate Via mask figure, then use the method that reactive ion RIE etches, use BCl₃/Cl₂SiC substrate is carried out by gas Etching, is etched to annular electrode surface always, forms through hole 12.

Step 12, evaporates Ti/Al/Ni/Au multilamellar with vacuum electron beam evaporation equipment successively at the back side of 4H-SiC substrate Metal, thickness is respectively 30nm/120nm/50nm/200nm, forms underlayer electrode through metal-stripping, injects metal After through hole 12 underlayer electrode is connected with annular electrode, constitute GaN Gunn diode negative electrode.

Step 13, puts into PECVD reative cell by the sample after above-mentioned steps processes, leads in reative cell simultaneously The silane entered and nitrogen, pressure be 40Torr, under conditions of temperature is 1000 DEG C, epitaxial growth thickness is 200nm SiN passivation layer.

Step 14, the method using RIE etching, use CF₄SiN passivation layer is performed etching by gas, is etched to always Circular electrode surface, forms perforate 11, exposes the anode of diode, complete the making of device, the gunn ultimately formed Diode chip section is as shown in Figure 1.

Embodiment 2: make the GaN Gunn diode of 6H-SiC semi-insulating type substrate.

Step one, organic semiconductor device:

Select the 6H-SiC semi-insulating type substrate of a diameter of 2 inches, the back side is carried out thinning, until substrate thickness is 150μm。

Step 2, epitaxial growth AlN nucleating layer:

Use the mode of MOCVD, under conditions of to keep pressure be 40Torr, temperature is 650 DEG C, be passed through simultaneously Trimethyl aluminium and nitrogen, at the AlN nucleating layer that 6H-SiC semi-insulating type Grown thickness is 40nm.

Step 3, epitaxial growth n⁺GaN cathode ohmic contact layer:

Use the mode of MOCVD, temperature is increased to 1060 DEG C, under conditions of keeping pressure to be 40Torr, with Time be passed through trimethyl gallium, nitrogen and N-shaped doped source silane, epitaxial growth thickness is 150nm, and doping content is 1.5×10¹⁸cm^-3N⁺GaN cathode ohmic contact layer.

Step 4, epitaxial growth electron emission layer:

4.1) n will have been grown⁺The sample of GaN cathode ohmic contact layer is put in molecular beam epitaxy MBE reative cell, Setting pressure as 500Torr, temperature is 1060 DEG C,

4.2) in MBE reative cell, it is passed through trimethyl gallium, nitrogen and trimethyl aluminium simultaneously, and being passed through of trimethyl aluminium Measuring linearly increasing, epitaxial growth thickness is that 15nm, Al concentration of component is by the AlGaN of 0% linear gradient to 15% Layer；

4.3) being passed through trimethyl gallium and nitrogen to MBE reative cell more simultaneously, be not passed through trimethyl aluminium, epitaxial growth is thick Degree is the GaN layer of 15nm；This AlGaN layer and GaN layer constitute a cycle of superlattices；Finally repeat Grow 4 cycles, obtain electron emission layer.

Step 5, epitaxial growth n^-GaN active layer:

The sample that grown electron emission layer is put into MOCVD reative cell, set air pressure in reative cell as 40Torr, is passed through trimethyl gallium, nitrogen and N-shaped doped source silane simultaneously, in the condition keeping temperature to be 1060 DEG C Under, epitaxial growth thickness is 1 μm, and doping content is 1 × 10¹⁷cm^-3N^-GaN active layer.

Step 6, epitaxial growth n⁺GaN cathode ohmic contact layer:

Continue to use the mode of MOCVD, be passed through trimethyl gallium, nitrogen and N-shaped doped source silane simultaneously, Being 40Torr keeping air pressure, under conditions of temperature is 1060 DEG C, epitaxial growth thickness is 150nm, and doping content is 1.5×10¹⁸cm^-3N⁺GaN cathode ohmic contact layer, forms GaN epitaxial layer.

Step 7, the etching big round table surface of formation:

7.1) method using photoetching, forms the big circular mask pattern of a diameter of 40 μm on GaN epitaxial layer；

7.2) use reactive ion etching technology, use BCl₃/Cl₂GaN epitaxial layer is performed etching by gas, carves Erosion, to exposing 4H-SiC substrate surface, forms big round table surface.

Step 8, etching formation small circular table top:

8.1) method using photoetching, forms the coaxial small circular table top mask of a diameter of 15 μm on big round table surface Figure；8.2) use reactive ion etching RIE technology, use BCl₃/Cl₂Big round table surface is performed etching by gas, Etching depth enters into n⁺200nm in GaN cathode ohmic contact layer, forms small circular table top.

Step 9, formation circular electrode and annular electrode:

9.1) use the mode of vacuum electronic beam evaporation, evaporate Ti/Al/Ni/Au multilamellar gold successively at whole device surface Belonging to, thickness is respectively 35nm/125nm/55nm/165nm,

9.2) use metal lift-off techniques, form circular electrode and annular electrode.

Step 10, formation metal and the Ohmic contact of GaN:

In argon gas atmosphere, at a temperature of 950 DEG C, whole device is carried out the quick thermal annealing process of 50 seconds, shape Become GaN Ohmic contact.

Step 11, etching formation through hole 12:

11.1) method using photoetching, forms the via mask of 4 a diameter of 10 μm at the back side of 6H-SiC substrate Figure,

11.2) use reactive ion RIE lithographic technique, use BCl₃/Cl₂SiC substrate is performed etching by gas, always It is etched to annular electrode surface, forms through hole 12.

Step 12, the negative electrode of formation GaN Gunn diode:

12.1) using the mode of vacuum electronic beam evaporation, evaporating thickness successively at the back side of 6H-SiC substrate is 35nm The Au of Ni and 200nm of Al, 55nm of Ti, 125nm,

12.2) use metal lift-off techniques, form underlayer electrode, inject the through hole 12 after metal by underlayer electrode and ring Shape electrode is connected, and constitutes the negative electrode of GaN Gunn diode.

Step 13, epitaxial growth SiN passivation layer:

Use PECVD mode, the silane being simultaneously passed through and nitrogen, pressure be 40Torr, temperature be 1000 DEG C Under conditions of, the SiN passivation layer that sample Epitaxial growth thickness is 200nm after processing through above-mentioned steps.

Step 14, exposes the anode of diode:

The method using RIE etching, uses CF₄SiN passivation layer is performed etching by gas, is etched to circular electrode always Surface, forms perforate 11, exposes the anode of diode, complete the making of device, the Gunn diode pipe ultimately formed Core section is as shown in Figure 1.

Embodiment 3: make the GaN Gunn diode of 6H-SiC conducting type substrate.

Step A, organic semiconductor device:

Select the 6H-SiC conducting type substrate of a diameter of 2 inches, the back side is carried out thinning, until substrate thickness is 150μm。

Step B, makes AlN nucleating layer and n⁺GaN cathode ohmic contact layer:

In MOCVD reative cell, under conditions of holding pressure is 60Torr, temperature is 650 DEG C, it is passed through three simultaneously Aluminium methyl and nitrogen, at the AlN nucleating layer that 6H-SiC conducting type Grown thickness is 90nm；Continue to use MOCVD technique, is increased to 1100 DEG C by temperature, and holding pressure is 60Torr, then is passed through trimethyl gallium, nitrogen simultaneously Gas and N-shaped doped source silane, epitaxial growth n⁺GaN cathode ohmic contact layer, the thickness of this ohmic contact layer is 400nm, doping content is 2 × 10¹⁸cm^-3。

Step C, epitaxial growth electron emission layer:

N will be grown⁺The sample of GaN cathode ohmic contact layer is put in molecular beam epitaxy MBE reative cell, to Reative cell is passed through trimethyl gallium, nitrogen and trimethyl aluminium simultaneously, and trimethyl aluminium be passed through metering the most linearly increasing after Stopping is passed through, and is 600Torr keeping pressure, under conditions of temperature is 1100 DEG C, 6 cycles of epitaxial growth AlGaN/GaN superlattices, the AlGaN layer thickness in each cycle is 20nm, and GaN layer thickness is 20nm, AlGaN In Ceng, Al concentration of component is from bottom to up by 0% linear gradient to 15%, forms electron emission layer.

Step D, epitaxial growth n^-GaN active layer and n⁺GaN anode ohmic contact layer:

The sample that grown electron emission layer is put in MOCVD reative cell, sets air pressure as 60Torr, with Time be passed through trimethyl gallium, nitrogen and N-shaped doped source silane to MOCVD reative cell, be 1100 DEG C in temperature Under the conditions of, epitaxial growth thickness is 2 μm, and doping content is 2 × 10¹⁷cm^-3N^-GaN active layer；Continue to use The mode of MOCVD, is passed through trimethyl gallium, nitrogen and N-shaped doped source silane to MOCVD reative cell simultaneously, Being 60Torr keeping air pressure, under conditions of temperature is 1100 DEG C, epitaxial growth thickness is 400nm, and doping content is 2×10¹⁸cm^-3N⁺GaN anode ohmic contact layer, forms GaN epitaxial layer.

Step E, forms big round table surface:

Utilize photoetching technique, GaN epitaxial layer is formed the big circular mask pattern of a diameter of 60 μm；Use Reactive ion etching technology, uses BCl₃/Cl₂GaN epitaxial layer is performed etching by gas, is etched to expose 4H-SiC Till substrate surface, form big round table surface.

Step F, formation small circular table top:

Utilize photoetching technique, big round table surface is formed the coaxial small circular table top mask pattern of a diameter of 20 μm； Use reactive ion etching RIE technology, use BCl₃/Cl₂Big round table surface is performed etching by gas, and etching depth enters To n⁺200nm in GaN cathode ohmic contact layer, forms small circular table top.

Step G, formation circular electrode and annular electrode:

Use the mode of vacuum electronic beam evaporation, evaporate Ti/Al/Ni/Au multiple layer metal successively at whole device surface, its Thickness is respectively 35nm/125nm/55nm/165nm；Use metal lift-off techniques, form circular electrode and annular electrode.

Step H, the Ohmic contact of formation GaN:

In argon gas atmosphere, at a temperature of 950 DEG C, whole device is carried out the quick thermal annealing process of 50 seconds, shape Become GaN Ohmic contact.

Step I, formation through hole 12 and the negative electrode of Gunn diode:

First with photoetching technique, form the via mask figure of 4 a diameter of 10 μm at the back side of 6H-SiC substrate； Use reactive ion RIE lithographic technique again, use BCl₃/Cl₂SiC substrate is performed etching by gas, is etched to ring always Shape electrode surface, forms through hole 12；Then the mode of vacuum electronic beam evaporation is used, at the back side of 6H-SiC substrate Evaporate the Au of Ni and 200nm of Al, 55nm of Ti, 125nm that thickness is 35nm successively；Finally use Metal lift-off techniques, forms underlayer electrode, injects the through hole 12 after metal and is connected with annular electrode by underlayer electrode, Constitute the negative electrode of GaN Gunn diode.

Step K, epitaxial growth SiN passivation layer:

Use PECVD mode, the silane being simultaneously passed through and nitrogen, pressure be 60Torr, temperature be 1100 DEG C Under conditions of, the SiN passivation layer that sample Epitaxial growth thickness is 400nm after processing through above-mentioned steps.

Step L, formation Gunn diode anode:

The method using RIE etching, uses CF₄SiN passivation layer is performed etching by gas, is etched to circular electrode always Surface, forms perforate 11, exposes the anode of diode, complete the making of device, the Gunn diode pipe ultimately formed Core section is as shown in Figure 1.

Claims (7)

1. based on an AlGaN/GaN superlattices electron emission layer GaN Gunn diode, including main part and auxiliary body portion, This main part includes from bottom to top: SiC substrate (1), AlN nucleating layer (2), n⁺GaN cathode ohmic contact layer (3), electron emission layer (4), n^-GaN active layer (5) and n⁺GaN anode ohmic contact layer (6)；Auxiliary body portion Including annular electrode (7), underlayer electrode (8), circular electrode (9), passivation layer (10) perforate (11) and through hole (12)；Annular electrode (7) and underlayer electrode (8), as the negative electrode of device, lay respectively at n⁺GaN cathode ohmic contact The top of layer (3) and the lower section of SiC substrate (1), circular electrode (9) is positioned at n as the anode of device⁺GaN anode Europe The top of nurse contact layer (6), passivation layer (8) is positioned at annular electrode (7) and the top of circular electrode (9)；Perforate (11) Laying respectively in passivation layer (10) and SiC substrate (1) with through hole (12), through hole (12) is by annular electrode (7) and lining Hearth electrode (8) is connected, and forms longitudinal device architecture；

It is characterized in that: electron emission layer (4) uses AlGaN/GaN superlattices, and these superlattices are provided with 4～6 cycles, each GaN layer thickness in cycle is 10-20nm, and AlGaN layer thickness is the Al concentration of component in 10-20nm, and AlGaN layer From bottom to up by 0% linear gradient to 15%.

2. AlGaN/GaN superlattices electron emission layer GaN Gunn diode as claimed in claim 1, it is characterised in that SiC Substrate (1) selects 4H-SiC semi-insulating type substrate or 6H-SiC semi-insulating type substrate or 6H-SiC conducting type substrate.

3. AlGaN/GaN superlattices electron emission layer GaN Gunn diode as claimed in claim 1, it is characterised in that AlN The thickness of nucleating layer (2) is 30～60nm.

4. AlGaN/GaN superlattices electron emission layer GaN Gunn diode as claimed in claim 1, it is characterised in that n⁺The thickness of GaN cathode ohmic contact layer (3) is 100～400nm, and doping content is 1～2 × 10¹⁸cm^-3。

5. AlGaN/GaN superlattices electron emission layer GaN Gunn diode as claimed in claim 1, it is characterised in that n^- The thickness of GaN active layer (4) is 0.5～2 μm, and doping content is 0.5～2 × 10¹⁷cm^-3。

6. AlGaN/GaN superlattices electron emission layer GaN Gunn diode as claimed in claim 1, it is characterised in that n⁺The thickness of GaN anode ohmic contact layer (5) is 100～400nm, and doping content is 1～2 × 10¹⁸cm^-3。

7. a manufacture method based on AlGaN/GaN superlattices electron emission layer GaN Gunn diode, enters according to the following procedure OK:

(1) epitaxial growth AlN nucleating layer:

The method using metal organic chemical vapor deposition MOCVD, on N-shaped or insulated type SiC substrate, epitaxial growth is thick Degree is the AlN nucleating layer of 30～90nm；

(2) epitaxial growth n⁺GaN cathode ohmic contact layer:

On the AlN nucleating layer of extension, by the method for metal organic chemical vapor deposition MOCVD, epitaxial growth doping is dense Degree is 1～2 × 10¹⁸cm^-3, thickness be 100～400nm n⁺GaN cathode ohmic contact layer；

(3) epitaxial growth electron emission layer:

3.1) at the n of extension⁺On GaN cathode ohmic contact layer, utilize molecular beam epitaxy MBE technology, first epitaxial growth thickness For 10-20nm, Al concentration of component from bottom to up by the AlGaN layer of 0% linear gradient to 15%；Continue to use MBE skill Art, epitaxial growth thickness is the GaN layer of 10-20nm, and this GaN layer constitutes a cycle of superlattices with AlGaN layer；

3.2) repeated growth 3-5 the cycle, electron emission layer is formed；

(4) epitaxial growth n^-GaN active layer:

On AlGaN/GaN superlattices electron emission layer, the method utilizing metal organic chemical vapor deposition MOCVD, outward Epitaxial growth doping content is 0.5～2 × 10¹⁷cm^-3, thickness be the n of 0.5～2 μm^-GaN active layer；

(5) epitaxial growth n⁺GaN anode ohmic contact layer:

At described n^-On GaN active layer, the method utilizing metal organic chemical vapor deposition MOCVD, epitaxial growth is adulterated Concentration is 1～2 × 10¹⁸cm^-3, thickness be 100～400nm n⁺GaN anode ohmic contact layer；

(6) the big round table surface of etching formation:

Use reactive ion etching technology that the epitaxial layer in SiC substrate is performed etching, be etched to the upper surface of SiC substrate always, To form a diameter of d₀Big round table surface, wherein 30 μm < d₀<60μm；

(7) etching formation small circular table top:

Described big round table surface continues use lithographic technique, form a diameter of d₁Small circular table top, etching depth to n⁺GaN Cathode ohmic contact layer, 10 μm < d₁<20μm；

(8) circular electrode and annular electrode are formed:

8.1) vacuum electron beam evaporation technique is used, at the n that small circular table top and etching expose⁺Form sediment on GaN cathode ohmic contact layer Long-pending Ti/Al/Ni/Au multiple layer metal,

8.2) use metal lift-off techniques, small circular table top forms the anode of circular electrode, i.e. Gunn diode, in negative electrode Europe Annular electrode is formed in nurse contact aspect；

(9) formation metal and the Ohmic contact of GaN:

At a temperature of 950 DEG C, it is passed through Ar₂The time of carrying out is the rapid thermal annealing of 50 seconds, makes n⁺GaN and circular electrode metal And between annular electrode metal, form Ohmic contact；

(10) etching formation through hole:

Use reactive ion etching technology, form n through hole, n in surface on back side of SiC substrate etching=1, etching depth is to annular electro Pole；

(11) negative electrode of formation GaN Gunn diode:

At SiC through hole and the surface on back side of SiC substrate deposit Ti/Al/Ni/Au multiple layer metal of etching formation, form anode substrate electricity Pole, underlayer electrode is connected together with electrode with annular and constitutes Gunn diode negative electrode；

(12) epitaxial growth SiN passivation layer expose the anode of diode:

12.1) method of employing PECVD is at the SiN passivation layer that device front deposition thickness is 200～400nm,

12.2) use reactive ion etching technology to form perforate 11 on small circular table top, expose Gunn diode anode.