CN115810674A

CN115810674A - Gallium nitride based resonant tunneling diode with multi-region differential negative resistance characteristic and manufacturing method thereof

Info

Publication number: CN115810674A
Application number: CN202211575030.6A
Authority: CN
Inventors: 薛军帅; 姚佳佳; 吴冠霖; 郭壮; 刘仁杰; 赵澄; 李泽辉; 袁金渊; 张进成; 郝跃
Original assignee: Xidian University
Current assignee: Xidian University
Priority date: 2022-12-08
Filing date: 2022-12-08
Publication date: 2023-03-17

Abstract

The invention discloses a gallium nitride-based resonant tunneling diode with multi-region differential negative resistance characteristics and a manufacturing method thereof, and mainly solves the problems that the existing gallium nitride resonant tunneling diode is difficult to realize multi-region differential negative resistance characteristics, low in series integration level and poor in consistency of the differential negative resistance characteristics. The GaN-based solar cell comprises a substrate, a GaN epitaxial layer, an emitting electrode ohmic contact layer, a multi-layer composite active region, a collector electrode ohmic contact layer and a collector electrode from bottom to top; the multi-layer composite active region consists of N active regions and N-1N layers ⁺ The GaN series layers are alternately arranged to form a composite structure; each layer of active areaThe quantum well layer comprises an isolation layer, a barrier layer, a quantum well layer, a barrier layer and an isolation layer from bottom to top; the barrier layers are made of wide-band-gap semiconductor materials. The invention has a plurality of differential negative resistance effects with the same peak current, stable device performance, good consistency of the differential negative resistance effects, high reliability and integration level, can eliminate metal interconnection of a plane series connection process, and can be used in a multi-value logic digital circuit and a memory.

Description

Gallium nitride-based resonant tunneling diode with multi-region differential negative resistance characteristic and manufacturing method thereof

Technical Field

The invention belongs to the technical field of semiconductor devices, and particularly relates to a gallium nitride-based resonant tunneling diode which can be used in a multi-valued logic digital circuit and a memory.

Background

The resonant tunneling diode is a quantum effect device with a vertical structure, has the characteristics of differential negative resistance, low junction capacitance, short carrier transport time, unipolar transport and the like, and has the working frequency capable of reaching a terahertz frequency band. The oscillator prepared based on the resonant tunneling diode device has the advantages of high frequency and low power consumption, is one of ways for realizing the terahertz radiation source, and has wide application in security detection, spectral imaging, broadband wireless communication and circuit design. Compared with GaAs materials, the GaN material has the advantages of wide forbidden band, high saturated electron speed and high thermal stability, and the GaN resonant tunneling diode can realize higher high frequency and higher high power output at room temperature. GaN materials have different crystal structures and polarization characteristics and multiple crystal planes, which gives more freedom to device structural design. The research on the physical mechanism related to vertical transport in the GaN resonant tunneling diode is the basis for realizing the GaN quantum cascade laser with a complex structure.

The high peak-to-valley current ratio differential negative resistance characteristic also provides support for GaN digital circuit design. The appearance of the differential negative resistance characteristic of the GaN resonant tunneling diode depends on the alignment of a discrete energy level in a double-barrier single quantum well and a two-dimensional electron gas energy level of an emitter, and theoretically, the alignment process can be realized for many times, so that the multi-region differential negative resistance characteristic appears, a foundation is provided for realizing a multi-value logic digital circuit, and the circuit function can be realized by less devices. However, due to the strong polarization effect and the asymmetry of the energy band of nitride materials, only one differential negative resistance region can generally appear.

In order to realize the multi-region differential negative resistance characteristic GaN resonant tunneling diode, a multi-quantum well structure can be adopted. In the output characteristic of the structural device, the difference between the peak current and the peak-to-valley current ratio of differential negative resistance characteristics in different areas is too large, so that the structural device is difficult to be applied to the monolithic integration of a digital logic circuit. In addition, series integration of the GaN resonant tunneling diodes on the same wafer can be adopted to achieve multi-region differential negative resistance characteristics, but requirements for thickness uniformity and distribution fluctuation on epitaxial material sheets are extremely high, and technical challenges are brought to epitaxial growth and device manufacturing processes. The conventional GaN resonant tunneling diode structure is shown in FIG. 1, and comprises a substrate,GaNEpitaxial layer, n ⁺ The GaN-based emitter ohmic contact layer, the first GaN isolation layer, the first AlGaN barrier layer, the GaN quantum well layer, the second AlGaN barrier layer, the second GaN isolation layer and the n ⁺ Ohmic contact layer of GaN collector and collector at n ⁺ And the GaN emitter ohmic contact layer is provided with an annular emitter electrode. This device has the following disadvantages:

firstly, the differential negative resistance characteristic that the ratio of two peak currents to the peak-to-valley current is close is difficult to realize, and the differential negative resistance characteristic cannot be independently applied to a multi-logic digital circuit;

secondly, the multi-region differential negative resistance characteristic is realized by the series process integration of devices on the chip, the requirement on the on-chip consistency of the device performance is extremely high, a large amount of wafer area is consumed, and meanwhile, metal interconnection is needed, the device process is complex, and the fault-tolerant rate is low;

thirdly, realizing multi-region differential negative resistance characteristics through a multi-quantum well structure, causing the difference between the peak current and the peak-to-valley current ratio of the differential negative resistance characteristics of the device to be too large, which is not suitable for the design of a digital circuit, and simultaneously, the epitaxial growth of the multi-quantum well material can cause the problems of large fluctuation of material thickness and uneven distribution;

fourthly, self-oscillation phenomenon exists in the differential negative resistance characteristic, and the output characteristic curve of the device has chair-shaped bulges, so that the device is unstable in performance and low in reliability.

Disclosure of Invention

The invention aims to provide a gallium nitride-based resonant tunneling diode with multi-region differential negative resistance characteristic and a manufacturing method thereof aiming at the defects of the prior art, so as to improve the integration level and reliability of a device, reduce the requirement on the fluctuation of the thickness of a multi-quantum well material, avoid the complexity of a metal interconnection process required by the series connection of devices on a chip and the inconsistency of the performance of the devices, and realize the differential negative resistance effect that the ratio of a plurality of peak currents to a peak-to-valley current is nearly the same.

The technical scheme of the invention is realized as follows:

1. a gallium nitride-based resonant tunneling diode with multi-region differential negative resistance effect comprises a substrate, a GaN epitaxial layer, an emitter ohmic contact layer, an active region, a collector ohmic contact layer, a collector electrode and annular emitter electrodes arranged on two sides of the active region from bottom to top; the active region is the cylinder mesa that the electrode of collector was formed for the sculpture, and this cylinder mesa outside parcel has passivation layer, its characterized in that:

the active region comprises N active regions and N-1N layers ⁺ The GaN series layers are arranged alternately to form a composite structure, and the doping concentration between each two active regions is 1 multiplied by 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 30nm to 200nm ⁺ And the GaN series connection layers are connected to realize differential negative resistance characteristics with the ratio of a plurality of peak currents to a peak-to-valley current being close, wherein N is more than or equal to 2.

Furthermore, each layer of the active region of the composite structure comprises a first isolation layer, a first barrier layer, a quantum well layer, a second barrier layer and a second isolation layer from bottom to top;

the thickness of the first isolation layer and the second isolation layer are GaN of 4nm-15 nm;

the first barrier layer and the second barrier layer have the same components, the thicknesses of the first barrier layer and the second barrier layer are both 1nm-3nm, and the thicknesses of the first barrier layer and the second barrier layer are the same;

the quantum well layer adopts In with the composition v between 0 and 100 percent _v Ga _1-v N, the thickness of which is 1nm-3nm.

Further, the first barrier layer and the second barrier layer are made of the same material and can be both Sc _x Al _1-x N、Y _x Al _1-x N、B _w Al _y Ga _z N, wherein the component x is between 5% and 25%, the components w, y and z are between 0% and 100%, and w + y + z =100%.

Further, the collector ohmic contact layer has a doping concentration of 5 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 50nm to 200nm ⁺ GaN; the ohmic contact layer of the emitter has a doping concentration of 5 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 50nm to 200nm ⁺ GaN; the thickness of the GaN epitaxial layer is 500nm-5000nm;

further, the passivation layer adopts SiN material and Al ₂ O ₃ Material, hfO ₂ Any one of the materials; the substrate is made of any one of a self-supporting gallium nitride single crystal material, a self-supporting aluminum nitride single crystal material, a sapphire material, a silicon carbide material, a silicon material, a boron nitride material and a diamond material.

2. A method for manufacturing a gallium nitride-based resonant tunneling diode with a multi-differential negative resistance effect is characterized by comprising the following steps of:

1) Epitaxially growing a GaN epitaxial layer of 500nm-5000nm on the substrate by adopting a molecular beam epitaxy method or a metal organic chemical vapor deposition method;

2) Growing n on GaN epitaxial layer by molecular beam epitaxy method ⁺ The thickness of the GaN emitter ohmic contact layer is 50nm-200nm, and the doping concentration is 5 multiplied by 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 ；

3) By molecular beam epitaxy method at n ⁺ Alternately growing an active region of a multilayer composite structure on the GaN emitter ohmic contact layer:

3a) Growing a first layer of active region:

3a1) At n ⁺ A GaN first isolating layer with the thickness of 4nm-15nm is grown on the GaN emitter ohmic contact layer;

3a2) Growing Sc with the thickness of 1nm-3nm and the component x between 5% and 25% on the GaN first isolation layer _x Al _1-x N or Y _x Al _1-x N; or B with the components w, y and z of 0-100%, w + y + z =100% and the thickness of 1nm-3nm _w Al _y Ga _z A first barrier layer of N;

3a3) Growing In with the composition v of 0-100% and the thickness of 1-3 nm on the first barrier layer _v Ga _1-v An N quantum well layer;

3a4) Growing a second barrier layer having the same composition and thickness as the first barrier layer on the quantum well layer;

3a5) Growing a GaN second isolating layer with the thickness of 4nm-15nm on the second barrier layer to finish the growth of the first active region;

3b) Growing the doped layer with a doping concentration of 1 × 10 on the first active region by molecular beam epitaxy ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 A first layer n having a thickness of 30nm to 200nm ⁺ A GaN series layer;

3c) In the first layer n ⁺ Generating a second active region on the GaN series layer according to the process flow of 3 a), and finishing the growth of the active region with a composite structure of two active regions and one series layer; sequentially and circularly growing to finally form an active region of a multilayer composite structure with N active regions and N-1 series layers;

4) Growing n on the active region of the composite structure by molecular beam epitaxy ⁺ The GaN collector ohmic contact layer has a thickness of 50-200 nm and a doping concentration of 5 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 ；

5) Using conventional optical lithography process, at n ⁺ GaN collector ohmic contact layerForming a device mesa isolation pattern, using photoresist as a mask, adopting an inductively coupled plasma etching method, and using BCl ₃ /Cl ₂ A gas source for etching the epitaxial material to form a mesa isolation with a depth of 650nm-1200 nm;

6) Using electron beam lithography at n ⁺ Forming a circular pattern with the diameter of 0.5-20 μm on the GaN collector ohmic contact layer, and performing electron beam evaporation on n with the photoresist as mask ⁺ Evaporating a Ti/Au/Ni metal layer on the ohmic contact layer of the GaN collector to form a collector electrode, and then using BCl by using an inductively coupled plasma etching method and using metal as a mask ₃ /Cl ₂ Gas source, etching depth to n ⁺ The GaN emitter ohmic contact layer forms a cylindrical table top from the first active layer to the collector electrode;

7) Using conventional optical lithography process, at n ⁺ Forming a ring pattern with an inner circumference distance of 3 μm from the cylindrical table top on the GaN emitter ohmic contact layer, and evaporating n by electron beam evaporation with photoresist as mask ⁺ Evaporating a Ti/Au metal layer on the GaN emitter ohmic contact layer (3) to form an emitter electrode;

8) Using plasma enhanced chemical vapor deposition or atomic layer deposition process at n ⁺ Depositing a passivation layer with the thickness of 50nm-200nm from the GaN emitter ohmic contact layer to the surface of the collector electrode;

9) And forming an emitter electrode through hole pattern on the passivation layer by adopting a traditional optical photoetching process. Using photoresist as mask, adopting reactive ion etching method, using SF ₆ A gas source forming an emitter electrode through hole;

10 Using an electron beam lithography process to form a circular pattern having a diameter of 200nm-18 μm on the passivation layer of the cylindrical mesa. Using photoresist as mask, adopting reactive ion etching method, using SF ₆ A gas source forming a collector electrode through hole;

11 Adopting a traditional optical photoetching process, forming an emitter and a collector Pad pattern on the surface of the device, evaporating a Ti/Au metal layer on the surface of the whole device by adopting an electron beam evaporation method by taking photoresist as a mask to form the emitter and the collector Pad, and finishing the preparation of the device.

Compared with the prior art, the invention has the following advantages:

1. the invention is provided with N layers of active regions and N-1 layers of N ⁺ The multilayer composite structure active area that the GaN series connection layer is constituteed, the resonance tunneling phenomenon that every active area of accessible takes place uses single device to realize multizone differential negative resistance characteristic, not only can avoid with the on-chip series connection integration of a plurality of devices on the horizontal direction, saves the wafer area, improves the device integration level, can avoid the metal interconnection of on-chip device integration technology moreover, preparation simple process, and the fault-tolerant rate promotes.

2. According to the active region with the multilayer composite structure, each active region and the series layer are realized in the epitaxial direction, so that the consistency of the thickness of epitaxial materials is ensured, the large performance deviation of devices on a chip caused by material thickness fluctuation and uneven distribution is avoided, and the survival rate and the reliability of the devices are improved.

3. The invention adopts n ⁺ GaN series connection layer feeds through a plurality of active areas in the vertical direction, not only can be through changing series connection layer thickness and doping concentration, effectively adjust the self-excited oscillation frequency in resonant tunneling diode differential negative resistance district, eliminate the arch of output characteristic curve "chair form", improve device stability and reliability, and can avoid adopting the multiple quantum well in the single active area when realizing multizone differential negative resistance characteristic, multizone differential negative resistance characteristic peak current density and the problem that the peak-valley current ratio phase difference is too big, device stability and reliability have further been promoted.

Drawings

FIG. 1 is a structural diagram of a conventional AlGaN/GaN double-barrier resonant tunneling diode;

FIG. 2 is a structural diagram of a GaN-based resonant tunneling diode with multi-region differential negative resistance characteristics according to the present invention;

FIG. 3 is a general flow chart of the fabrication of a GaN-based resonant tunneling diode with multi-region differential negative resistance characteristics according to the present invention;

FIG. 4 shows the fabrication of a semiconductor device including 2 active regions and 1n layer ⁺ Flow schematic diagram of composite active region formed by alternately arranging GaN series layers；

FIG. 5 shows the fabrication of a semiconductor device including 4 active regions and 3n layers according to the present invention ⁺ A flow schematic diagram of a composite active region formed by alternately arranging GaN series layers;

FIG. 6 shows a method of fabricating a semiconductor device including 6 active regions and 5n layers according to the present invention ⁺ A flow schematic diagram of a composite active region 6 layer composite active region formed by alternately arranging GaN series layers;

fig. 7 shows the test results of the I-V dc characteristic curve of the first embodiment.

Detailed Description

Embodiments and effects of the present invention will be further described with reference to the accompanying drawings.

Referring to fig. 2, the gallium nitride-based resonant tunneling diode with the multi-characteristic differential negative resistance characteristic of the invention comprises a substrate 1, a GaN epitaxial layer 2, an emitter ohmic contact layer 3, a composite active region 4, a collector ohmic contact layer 5, a collector electrode 6, and annular emitter electrodes 8 arranged on two sides of the active region from bottom to top; the active region 4 to the collector electrode 6 is an etched cylindrical mesa, which is externally wrapped with a passivation layer 7.

The composite active region 4 is composed of N layers of active regions and N-1 layers of N ⁺ The GaN series layer is arranged alternately to form a composite structure, wherein the active region of each layer comprises a first isolation layer 41, a first barrier layer 42, a quantum well layer 43, a second barrier layer 44 and a second isolation layer 45 from bottom to top; n of each layer ⁺ GaN tandem layer with doping concentration of 1 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 30nm to 200nm ⁺ GaN, wherein N is more than or equal to 2.

The thicknesses of the first isolation layer 41 and the second isolation layer 45 are GaN of 4nm-15 nm;

the first barrier layer 42 and the second barrier layer 44 have the same composition, and the thicknesses thereof are both 1nm to 3nm and are the same;

the quantum well layer 43 employs In with a composition v between 0% and 100% _v Ga _1-v N, the thickness of which is 1nm-3nm;

the first barrier layer 42 and the second barrier layer 44 are made of the same material, and both can be made of Sc _x Al _1-x N、Y _x Al _1-x N、B _w Al _y Ga _z N, wherein the x is 5-25%, the w, y and z are 0-100%, and w + y + z =100%;

the collector ohmic contact layer 5 has a doping concentration of 5 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 50nm to 200nm ⁺ GaN；

The emitter ohmic contact layer 3 has a doping concentration of 5 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 50nm to 200nm ⁺ GaN；

The thickness of the GaN epitaxial layer 2 is 500nm-5000nm;

the passivation layer 7 is made of SiN material and Al ₂ O ₃ Material, hfO ₂ Any one of the materials;

the substrate 1 is made of any one of a self-supporting gallium nitride single crystal material, a self-supporting aluminum nitride single crystal material, a sapphire material, a silicon carbide material, a silicon material, a boron nitride material and a diamond material.

Referring to fig. 3, the gallium nitride based resonant tunneling diode with multi-region differential negative resistance characteristic manufactured by the present invention provides the following 6 examples.

Example one, the method uses Sc on a free-standing GaN single crystal substrate _0.18 Al _0.82 And the N barrier layer and the GaN quantum well are ScAlN/GaN two-region differential negative resistance-characteristic gallium nitride-based resonant tunneling diodes.

Step one, growing a GaN epitaxial layer.

A molecular beam epitaxy method is adopted to grow a GaN epitaxial layer with the thickness of 1500nm on a self-supporting gallium nitride substrate.

The technological conditions adopted for growing the GaN epitaxial layer are as follows: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^- ⁷ The nitrogen flow rate was 1.8sccm with a nitrogen plasma RF source power of 375W.

Step two, growing n ⁺ And the GaN emitter ohmic contact layer.

By adopting a molecular beam epitaxy method, the method comprises the following steps of,the GaN epitaxial layer is grown to have a thickness of 100nm and a doping concentration of 1 × 10 ²⁰ cm ^-3 N of (a) ⁺ And a GaN emitter ohmic contact layer.

Growth of n ⁺ The process conditions of the GaN emitter ohmic contact layer are as follows: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^-7 Torr, equilibrium vapor pressure of silicon beam stream is 3.5X 10 ^-8 The nitrogen flow rate was 2.3sccm with a nitrogen plasma RF source power of 375W.

And step three, growing a composite active region.

Referring to FIG. 4, this step is embodied as follows

3.1 Grow the first active region:

3.1.1 By molecular beam epitaxy at n ⁺ A first GaN isolation layer 41 with a thickness of 10nm is grown on the GaN emitter ohmic contact layer, as shown in fig. 4 (a), under the following process conditions: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^- ⁷ The nitrogen flow is 2.3sccm, and the power of the nitrogen plasma radio frequency source is 375W;

3.1.2 A first Sc component of 18% is grown on the first GaN spacer layer to a thickness of 2nm by molecular beam epitaxy _0.18 Al _0.82 The N-barrier layer 42, as shown in fig. 4 (b), is processed under the following conditions: the temperature is 700 ℃, the nitrogen flow is 2.3sccm, and the equilibrium vapor pressure of scandium beam is 1.5 x 10 ^-8 Torr, equilibrium vapor pressure of aluminum beam current is 2.5X 10 ^-7 Torr, the power of nitrogen plasma radio frequency source is 375W;

3.1.3 A GaN quantum well layer 43 with a thickness of 2nm was grown on the first scann barrier layer by molecular beam epitaxy, as shown in fig. 4 (c), under the process conditions: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^-7 Torr, nitrogen flow rate is 2.3sccm, and nitrogen plasma radio frequency source power is 375W;

3.1.4 A second Sc component of 18% was grown on the GaN quantum well layer to a thickness of 2nm by molecular beam epitaxy _0.18 Al _0.82 The N-barrier layer 44, as shown in fig. 4 (d), has the following process conditions: the temperature is 700 ℃, the nitrogen flow is 2.3sccm, and the scandium beam equilibrium vapor pressure is 1.5 x 10 ^-8 Torr, aluminum beam current equilibrium steamingThe air pressure is 2.5 multiplied by 10 ^-7 Torr, the power of nitrogen plasma radio frequency source is 375W;

3.1.5 By molecular beam epitaxy method in a second Sc _0.18 Al _0.82 A second GaN spacer layer 45 is grown on the N-barrier layer as shown in fig. 4 (e) under the process conditions: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^-7 Torr, nitrogen flow rate is 2.3sccm, and nitrogen plasma radio frequency source power is 375W;

3.2 Using molecular beam epitaxy method, the first active region is grown to a thickness of 30nm and a doping concentration of 1 × 10 ²⁰ cm ^-3 N of (a) ⁺ The GaN tandem layer, as shown in fig. 4 (f), has the following process conditions: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^- ⁷ Torr, equilibrium vapor pressure of silicon beam current is 3.5X 10 ^-8 The nitrogen flow rate was 2.3sccm with a nitrogen plasma RF source power of 375W.

3.3 Grow a second active region:

3.3.1 By molecular beam epitaxy at n ⁺ A first GaN spacer 41 was grown on the GaN tandem layer to a thickness of 10nm as shown in fig. 4 (g) under the process conditions: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^-7 Torr, nitrogen flow rate is 2.3sccm, and nitrogen plasma radio frequency source power is 375W;

3.3.2 Using molecular beam epitaxy to grow a first Sc layer with a thickness of 2nm and a Sc component of 18% on the first GaN isolation layer _0.18 Al _0.82 The N-barrier layer 42, as shown in fig. 4 (h), is processed under the following conditions: the temperature is 700 ℃, the nitrogen flow is 2.3sccm, and the equilibrium vapor pressure of scandium beam is 1.5 x 10 ^-8 Torr, the equilibrium vapor pressure of aluminum beam is 2.5X 10 ^-7 Torr, the power of nitrogen plasma radio frequency source is 375W;

3.3.3 A GaN quantum well layer 43 with a thickness of 2nm is grown on the first ScAlN barrier layer by using a molecular beam epitaxy method, as shown in fig. 4 (i), under the process conditions: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^-7 Torr, nitrogen flow rate is 2.3sccm, and nitrogen plasma radio frequency source power is 375W;

3.3.4 Using molecular beam epitaxy method) to grow a thickness of 2n on the GaN quantum well layerm, sc component 18% of a second Sc _0.18 Al _0.82 The N-barrier layer 44, as shown in fig. 4 (j), is processed under the following conditions: the temperature is 700 ℃, the nitrogen flow is 2.3sccm, and the equilibrium vapor pressure of scandium beam is 1.5 x 10 ^-8 Torr, the equilibrium vapor pressure of aluminum beam is 2.5X 10 ^-7 Torr, the power of nitrogen plasma radio frequency source is 375W;

3.3.5 By molecular beam epitaxy method in a second Sc _0.18 Al _0.82 A second GaN spacer layer 45 is grown on the N-barrier layer as shown in fig. 4 (k) under the process conditions: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^-7 The nitrogen flow rate was 2.3sccm with a nitrogen plasma RF source power of 375W.

Step four, growing n ⁺ And a GaN collector ohmic contact layer as shown in FIG. 4 (l).

Growing the active region on the substrate by molecular beam epitaxy with a thickness of 100nm and a doping concentration of 1 × 10 ²⁰ cm ^-3 N of (A) to (B) ⁺ And a GaN collector ohmic contact layer.

Growth of n ⁺ The process conditions of the GaN collector ohmic contact layer are as follows: the temperature is 700 ℃, the equilibrium vapor pressure of the gallium beam is 8.0 multiplied by 10 ^-7 Torr, equilibrium vapor pressure of silicon beam current is 3.5X 10 ^-8 The nitrogen flow rate was 2.3sccm and the nitrogen plasma RF source power was 375W.

Step five, in n ⁺ And photoresist is homogenized, photoetching, developing and etching are carried out on the GaN collector ohmic contact layer to form a grid-shaped mesa isolation with the depth of 500 nm.

5.1 Photolithography is used to form mesa isolation patterns:

5.1.1 AZ5214 photoresist is spin-coated at a rotation speed of 500rad/min and an acceleration of 1000rad ² Spin coating for 3s under the condition of/min; then the rotation speed is 4000rad/min, the acceleration is 2000rad ² Spin coating for 30s at min, and baking for 90s at 95 deg.C;

5.1.2 Using conventional optical lithography, for n ⁺ Exposing AZ5214 photoresist on the GaN collector ohmic contact layer;

5.1.3 The photoresist after exposure treatment is developed by RZX-3038 developing solution for 45s to form a grid-shaped mesa isolation pattern.

5.2 Etching to form mesa isolation:

adopting an inductively coupled plasma etching method, taking photoresist as a mask, and etching to form a grid mesa isolation with the depth of 700nm, wherein the etching process conditions are as follows: cl ₂ The gas flow rate was 10sccm, BCl ₃ The flow rate was 25sccm and the etching time was 350s.

Step six, in n ⁺ Etching the ohmic contact layer of the GaN collector to n ⁺ And forming a cylindrical table top with the diameter of 2 mu m by using the GaN emitter ohmic contact layer, and depositing metal to form a collector electrode.

6.1 Lithography to form a circular mesa pattern:

6.1.1 In n) ⁺ Spin-coating PMMA A4 photoresist on the InN collector ohmic contact layer: firstly, the rotation speed is 500rad/min, the acceleration is 1000rad ² Spin coating for 3s under the condition of/min; then the rotating speed is 4000rad/min, the acceleration is 2000rad ² Spin-coating for 30s at min, and baking for 90s at 180 deg.C;

6.1.2 Adopting an electron beam lithography method, setting an electron dose ratio to be 750, and carrying out exposure treatment on the PMMA A4 photoresist;

6.1.3 ) first using a ratio of 3:1 and isopropanol solution, developing the photoresist after exposure for 120s, and fixing the photoresist for 30s by using the isopropanol to form a circular mesa pattern with the diameter of 2 mu m.

6.2 By electron beam evaporation on a circular table

Evaporating Ti/Au/Ni metal with the thickness of 20/80/50nm at the speed rate, and then soaking the Ti/Au/Ni metal in an acetone solution;

6.3 N) etching n with metal as mask by inductively coupled plasma etching ⁺ GaN collector ohmic contact layer to n ⁺ The GaN emitter ohmic contact layer forms a cylindrical table top with the diameter of 2 mu m, and the etching process conditions are as follows: cl ₂ The gas flow rate was 10sccm, BCl ₃ The gas flow was 25sccm and the etching time was 150s.

In the seventh step,at n ⁺ And a ring-shaped emitter electrode with the inner circumference being 3 mu m away from the cylindrical table top is formed on the GaN emitter ohmic contact layer.

7.1 Photolithography) to form a ring-shaped emitter electrode pattern:

7.1.1 In n) ⁺ An AZ5214 photoresist is spin-coated on the ohmic contact layer of the GaN emitter, and the photoresist is firstly spun at 500rad/min at 1000rad under the acceleration condition ² Spin coating for 3s at min; then the rotation speed is 4000rad/min, the acceleration is 2000rad ² Spin coating for 30s at min, and baking for 90s at 95 ℃;

7.1.2 Using conventional optical lithography, for n ⁺ Exposing AZ5214 photoresist on the GaN emitter ohmic contact layer;

7.1.3 The photoresist after exposure was developed for 45s using an RZX-3038 developer to form a ring-shaped emitter electrode pattern having an inner circumference of 3 μm from the cylindrical mesa.

7.2 By electron beam evaporation at n ⁺ On the ohmic contact layer of GaN emitter

The Ti/Au metal with the thickness of 20/80nm is evaporated at the rate of (2) and then soaked by acetone solution to form an emitter electrode with the inner circumference being 3 mu m away from the cylindrical table surface.

And step eight, depositing a passivation layer.

A plasma enhanced chemical vapor deposition method is adopted to deposit a SiN passivation layer with the thickness of 200nm on the surface of the whole device, and the process conditions are as follows: time 60s, pressure 2200mTorr, temperature 350 deg.C, siH ₄ The flow rate was 13.5sccm ₃ The flow rate was 10sccm, N ₂ The flow rate was 1000sccm.

And step nine, photoetching and etching the SiN passivation layer to form an emitter electrode through hole.

9.1 Photolithography to form an emitter electrode via pattern:

9.1.1 AZ5214 photoresist is spin-coated on the SiN passivation layer at a rotation speed of 500rad/min and an acceleration of 1000rad ² Spin coating for 3s under the condition of/min; then the rotation speed is 4000rad/min, the acceleration is 2000rad ² Downward rotation at minTransferring for 30s, and baking at 95 ℃ for 90s;

9.1.2 Conventional optical lithography is used to expose the AZ5214 photoresist on the SiN passivation layer;

9.1.3 Carrying out development on the photoresist subjected to exposure treatment for 45s by adopting RZX-3038 developing solution to form a circular ring pattern with the inner diameter slightly smaller than that of the emitter electrode;

9.2 Adopting a reactive ion etching method, taking the photoresist as a mask, etching the SiN passivation layer to the metal surface of the emitter electrode to form the through hole of the emitter electrode, wherein the process conditions are as follows: the pressure is 1500mTorr, the power is 200W ₆ Flow rate of 8sccm, CHF ₃ At a flow rate of 10sccm and a flow rate of 150sccm.

Step ten, preparing a collector electrode through hole with the diameter of 1 mu m on the passivation layer of the SiN.

10.1 Lithography to form a collector electrode via pattern:

10.1 a) PMMA A4 photoresist is spin-coated on the passivation layer of SiN, i.e. at a rotation speed of 500rad/min and an acceleration of 1000rad ² Spin coating for 3s under the condition of min; then the rotation speed is 4000rad/min, the acceleration is 2000rad ² Spin-coating for 30s under the condition of min, and then baking for 90s at 180 ℃;

10.1 b) setting the electron dose ratio to be 750, and carrying out exposure treatment on the PMMA A4 photoresist by adopting an electron beam lithography method;

10.1 c) for the photoresist after exposure treatment, firstly adopting a ratio of 3: developing the solution of tetramethyl-cyclopentanone and isopropanol of 1 for 120s, and fixing the solution for 30s by using isopropanol to form a through hole pattern of a collector electrode;

10.2 Using photoresist as a mask, etching the SiN passivation layer to the collector electrode metal by reactive ion etching

The surface of the glass is coated with a coating,

forming a through hole of a collector electrode with the diameter of 1 mu m, wherein the process conditions are as follows: the pressure is 1500mTorr, the power is 200W ₆ Flow rate of 8sccm, CHF ₃ At a flow rate of 10sccm, the He flow rate was 150sccm.

And step eleven, leading out an emitter electrode Pad and a collector electrode Pad from the emitter electrode through hole and the collector electrode through hole, and finishing the manufacture of the device.

11.1 Photolithography to form a pattern of emitter and collector metal Pad:

11.1 a) spin-coating AZ5214 photoresist on the through holes of the emitter and the collector, i.e. firstly, the rotation speed is 500rad/min, and the acceleration is 1000rad ² Spin coating for 3s under the condition of/min; then the rotation speed is 4000rad/min, the acceleration is 2000rad ² Spin coating for 30s at min, and baking for 90s at 95 deg.C;

11.1 b) adopting a traditional optical photoetching method to carry out exposure treatment on the AZ5214 photoresist;

11.1 c) developing the exposed photoresist for 45s by adopting an RZX-3038 developing solution to form a metal Pad pattern of an emitter electrode and a collector electrode;

11.2 Using electron beam evaporation method according to

Evaporating Ti/Au metal with the thickness of 20/80nm at the speed, and soaking the Ti/Au metal by using acetone to form an emitter electrode Pad and a collector electrode Pad which are interconnected with the emitter electrode and the collector electrode, thereby finishing the manufacture of the device.

Second embodiment, on the sapphire substrate, Y is adopted for fabrication _0.20 Al _0.80 The GaN-based resonant tunneling diode has the YAlN/InGaN four-region differential negative resistance characteristics of the N barrier layer and the InGaN quantum well.

Step 1, growing a GaN epitaxial layer.

Using molecular beam epitaxy method, gallium beam equilibrium vapor pressure is 8.5 × 10 at 720 deg.C ^-7 And growing a GaN epitaxial layer with the thickness of 5000nm on the sapphire substrate under the process conditions of the Torr, the nitrogen flow rate of 2.3sccm and the nitrogen plasma radio frequency source power of 375W.

Step 2, growing n ⁺ And the GaN emitter ohmic contact layer.

Using molecular beam epitaxy method, at 720 deg.C, the equilibrium vapor pressure of gallium beam is 8.5 × 10 ^-7 Torr, equilibrium vapor pressure of silicon beam current is 3.2X 10 ^-8 The Torr, the nitrogen flow is 2.3sccm, and the nitrogen plasma radio frequency source power is 375W, a thick GaN epitaxial layer is grownThe degree is 200nm, the doping concentration is 8 multiplied by 10 ¹⁹ cm ^-3 N of (a) ⁺ And the GaN emitter ohmic contact layer.

Step 3, growing four active regions and three n layers ⁺ And the GaN series layers are alternately arranged to form a composite active region.

Referring to FIG. 5, this step is embodied as follows

(3.1) growing the first layer active region, as shown in fig. 5 (a):

(3.1.1) molecular beam epitaxy method is used, with the temperature of 720 deg.C and the equilibrium vapor pressure of gallium beam at 8.5 × 10 ^- ⁷ The nitrogen flow is 2.3sccm, the nitrogen plasma radio frequency source power is 375W under the process condition of n ⁺ A first GaN isolating layer 41 with the thickness of 6nm is grown on the GaN emitting electrode ohmic contact layer;

(3.1.2) molecular Beam epitaxy method was used, with the temperature set at 720 deg.C, nitrogen flow 2.3sccm, and equilibrium vapor pressure of iridium beam at 1.8X 10 ^-8 Torr, equilibrium vapor pressure of aluminum beam current is 2.3X 10 ^-7 Torr, nitrogen plasma radio frequency source power is 375W, a first Y with the thickness of 1.5nm and the Y component of 20 percent is grown on the GaN isolation layer _0.2 Al _0.8 An N barrier layer 42;

(3.1.3) Using molecular Beam epitaxy method, the temperature was set at 720 ℃ and the equilibrium vapor pressure of indium beam was 2.0X 10 ^- ⁷ Torr, equilibrium vapor pressure of gallium beam current is 8.5 x 10 ^-7 Torr, nitrogen flow rate of 2.3sccm, and nitrogen plasma RF source power of 375W in the first Y _0.2 Al _0.8 An InGaN quantum well layer 43 with the thickness of 2.5nm is grown on the N barrier layer;

(3.1.4) molecular Beam epitaxy method was used, with the temperature set at 720 deg.C, nitrogen flow 2.3sccm, and equilibrium vapor pressure of iridium beam at 1.8X 10 ^-8 Torr, the equilibrium vapor pressure of aluminum beam is 2.3X 10 ^-7 Torr, the process condition of nitrogen plasma radio frequency source power of 375W, and a second Y with the thickness of 1.5nm and the Y component of 20 percent is grown on the InGaN quantum well layer _0.2 Al _0.8 An N barrier layer 44;

(3.1.5) molecular beam epitaxy method is adopted, wherein the temperature is 720 ℃, and the equilibrium vapor pressure of gallium beam is 8.5×10 ^- ⁷ Torr, nitrogen flow rate of 2.3sccm, and nitrogen plasma RF source power of 375W, in the second Y _0.2 Al _0.8 A second GaN isolating layer 45 with the thickness of 6nm is grown on the N barrier layer;

(3.2) Using molecular Beam epitaxy method, the temperature was set at 720 deg.C and the equilibrium vapor pressure of gallium Beam is 8.5X 10 ^- ⁷ Torr, equilibrium vapor pressure of silicon beam stream is 3.2X 10 ^-8 The process conditions of Torr, nitrogen flow of 2.3sccm and nitrogen plasma radio frequency source power of 375W are adopted, 50nm of thickness and doping concentration of 8 multiplied by 10 are grown on the first layer active area ¹⁹ cm ^-3 First layer n of ⁺ GaN series layer, as in fig. 5 (b).

(3.3) in the first layer n ⁺ Growing a second active region layer on the GaN series layer, as shown in fig. 5 (c), wherein the specific implementation of the step is the same as that of step (3.1);

(3.4) growing a second layer n on the second layer active region ⁺ GaN tandem layer, fig. 5 (d), the specific implementation of this step is the same as step (3.2);

(3.5) in the second layer n ⁺ Growing a third active region on the GaN series layer, as shown in fig. 5 (e), wherein the specific implementation of this step is the same as that of step (3.1);

(3.6) growing a third layer n on the third layer active region ⁺ GaN tandem layer, fig. 5 (f), the specific implementation of this step is the same as step (3.2);

(3.7) in the third layer n ⁺ Growing a fourth active region on the GaN series layer, as shown in FIG. 5 (g), wherein the specific implementation of this step is the same as that of step (3.1); completing four layers of active region and three layers of n ⁺ And growing a composite active region with the GaN series layers arranged alternately.

Step 4, growing n ⁺ And a GaN collector ohmic contact layer.

Using molecular beam epitaxy method, gallium beam equilibrium vapor pressure is 8.5 × 10 at 720 deg.C ^-7 Torr, equilibrium vapor pressure of silicon beam stream is 3.2X 10 ^-8 Growing the GaN epitaxial layer with the thickness of 200nm and the doping concentration of 8 multiplied by 10 under the process conditions of Torr, the nitrogen flow of 2.3sccm and the nitrogen plasma radio frequency source power of 375W ¹⁹ cm ^-3 N of (a) ⁺ And the GaN collector ohmic contact layer.

Step 5, in n ⁺ And photoresist is homogenized, photoetching, developing and etching are carried out on the GaN collector ohmic contact layer to form a grid-shaped mesa isolation with the depth of 800 nm.

(5.1) forming a mesa isolation pattern by photolithography, wherein the specific implementation of the step is the same as that of the step 5.1) in the first embodiment.

(5.2) adopting an inductively coupled plasma etching method, taking the photoresist as a mask and adopting Cl ₂ The gas flow rate was 10sccm, BCl ₃ Etching n under the process condition that the gas flow is 25sccm ⁺ And the GaN collector ohmic contact layer 400s forms a grid-shaped mesa isolation with the depth of 800 nm.

Step 6, at n ⁺ Etching the ohmic contact layer of the GaN collector to n ⁺ And forming a cylindrical table top with the diameter of 1 mu m by using the GaN emitter ohmic contact layer, and depositing metal to form a collector electrode.

(6.1) photoetching to form a circular mesa pattern:

(6.1.1) at n ⁺ Spin-coating PMMA A4 photoresist on the GaN collector ohmic contact layer twice: the first time at a rotation speed of 500rad/min and an acceleration of 1000rad ² Spin coating for 3s under the condition of min; the second rotation speed is 4000rad/min, and the acceleration is 2000rad ² Spin-coating for 30s under the condition of min, and then baking for 90s at the temperature of 180 ℃;

(6.1.2) adopting an electron beam lithography method, setting the electron dose ratio to be 750, and carrying out exposure treatment on the PMMA A4 photoresist;

(6.1.3) for the photoresist after exposure treatment, firstly adopting a ratio of 3:1, developing with isopropanol solution for 120s, and fixing with isopropanol for 30s to form a circular mesa pattern with a diameter of 1 μm.

(6.2) adopting an electron beam evaporation method, and performing electron beam evaporation on the circular table top pattern

The Ti/Au/Ni metal was evaporated to a thickness of 20/80/50nm and then soaked in an acetone solution.

(6.3) Using the metal as a mask, useEtching the circular mesa pattern by inductively coupled plasma etching method, and setting Cl ₂ The gas flow rate was 10sccm, BCl ₃ Etching to n under the process conditions of the gas flow of 25sccm and the etching time of 150s ⁺ And the GaN emitter ohmic contact layer forms a cylindrical table top with the diameter of 1 mu m.

Step 7, at n ⁺ And a ring-shaped emitter electrode with the inner circumference being 3 mu m away from the cylindrical table top is formed on the GaN emitter ohmic contact layer.

The specific implementation of this step is the same as step seven of the first embodiment.

Step 8, depositing 50nm Al ₂ O ₃ A dielectric passivation layer.

Using atomic layer deposition process, setting time at 40s, pressure at 2000mTorr, temperature at 300 deg.C, and Al (CH) ₃ ) ₃ The flow rate was 850sccm, H ₂ O flow rate is 350sccm, N ₂ The flow rate is 1000sccm, and Al with the thickness of 50nm is deposited on the whole surface of the device ₂ O ₃ A dielectric passivation layer.

Step 9, in Al ₂ O ₃ And photoetching and etching the dielectric passivation layer to form an emitter electrode through hole.

(9.1) photoetching to form an emitter electrode through hole pattern:

the specific implementation of this step is the same as step 9.1) of example one.

(9.2) with the photoresist as a mask, adopting a reactive ion etching method, setting the pressure to be 1500mTorr and the power to be 200W ₆ Flow rate of 8sccm, CHF ₃ Etching Al under the process conditions of 10sccm and 150sccm He flow ₂ O ₃ And (4) a medium passivation layer reaches the metal surface of the emitter electrode to form an emitter electrode through hole.

Step 10, in Al ₂ O ₃ And preparing a collector electrode through hole with the diameter of 500nm on the medium passivation layer.

(10.1) forming a collector electrode through hole pattern by photoetching:

the specific implementation of this step is the same as step 10.1) of the first embodiment.

(10.2) using the photoresist as a mask, adopting a reactive ion etching method under the pressure of1500mTorr, power 200W ₆ Flow rate of 8sccm, CHF ₃ Etching Al under the process conditions of 10sccm and 150sccm He flow ₂ O ₃ And (5) passivating the medium layer to the metal surface of the collector electrode to form a collector electrode through hole with the diameter of 500 nm.

And 11, leading out an emitter electrode Pad and a collector electrode Pad from the through holes of the emitter electrode and the collector electrode to finish the manufacture of the device.

The specific implementation of this step is the same as step eleven of embodiment one.

In the third embodiment, a GaN-based resonant tunneling diode with differential negative resistance characteristics in six AlN/GaN regions is fabricated on a silicon substrate using an AlN barrier layer and a GaN quantum well.

And step A, growing a GaN epitaxial layer.

Using molecular beam epitaxy method, at 650 deg.C, the equilibrium vapor pressure of gallium beam is 4.5 × 10 ^-7 And growing a GaN epitaxial layer with the thickness of 500nm on the silicon substrate under the process conditions of the Torr, the nitrogen flow rate of 1.2sccm and the nitrogen plasma radio frequency source power of 375W.

Step B, growing n ⁺ And a GaN emitter ohmic contact layer.

Adopting molecular beam epitaxy method, gallium beam equilibrium vapor pressure is 7.5 × 10 at 650 deg.C ^-7 Torr and equilibrium vapor pressure of silicon beam current is 3.0X 10 ^-8 Growing the GaN epitaxial layer with the thickness of 300nm and the doping concentration of 5 × 10 under the process conditions of Torr, nitrogen flow of 2.3sccm and nitrogen plasma radio frequency source power of 375W ¹⁹ cm ^-3 N of (A) to (B) ⁺ And a GaN emitter ohmic contact layer.

Step C, growing six active regions and five n layers ⁺ And the GaN series layers are alternately arranged to form a composite active region.

Referring to fig. 6, the specific implementation of this step is as follows:

c.1 Grow the first active region, as in fig. 6 (a):

c.1.1 By molecular beam epitaxy at 650 deg.C and equilibrium vapor pressure of gallium beam of 7.5 × 10 ^- ⁷ Torr, nitrogen flow of 2.3sccm, nitrogen plasma radio frequencyUnder the process condition that the source power is 375W, n ⁺ A first GaN isolating layer 41 with the thickness of 4nm is grown on the GaN emitter ohmic contact layer;

c.1.2 ) by molecular beam epitaxy at 650 deg.C under nitrogen flow of 2.3sccm and gallium beam equilibrium vapor pressure of 7.5 × 10 ^-7 Torr and the equilibrium vapor pressure of aluminum beam is 2.8X 10 ^-7 Under the process conditions of Torr and nitrogen plasma RF source power of 375W, a first AlN barrier layer 42 with a thickness of 3nm was grown on the first GaN spacer layer 41.

C.1.3 By molecular beam epitaxy at 680 deg.C and equivalent equilibrium vapor pressure of gallium beam of 7.5 × 10 ^- ⁷ A GaN quantum well layer 43 with a thickness of 3nm was grown on the first AlN barrier layer 42 under the process conditions of Torr, a nitrogen flow rate of 2.3sccm, and a nitrogen plasma radio frequency source power of 375W.

C.1.4 By molecular beam epitaxy at 650 deg.C, nitrogen flow of 2.3sccm, and balanced vapor pressure of gallium beam of 7.5 × 10 ^-7 The equilibrium vapor pressure of Torr and aluminum beam is 2.8X 10 ^-7 Under the process conditions of Torr and nitrogen plasma RF source power of 375W, a second AlN barrier layer 44 with a thickness of 3nm was grown on the GaN quantum well layer 43.

C.1.5 By molecular beam epitaxy at 530 deg.C under 2.3sccm flow of nitrogen and 7.5 × 10 vapor pressure of gallium beam equilibrium ^-7 Under the process conditions of Torr and nitrogen plasma radio frequency source power of 375W, a GaN isolation layer 45 with a thickness of 4nm was grown on the second AlN barrier layer 44.

C.2 Growth of the first layer n) ⁺ GaN tandem layer, fig. 6 (b):

adopting molecular beam epitaxy method, gallium beam equilibrium vapor pressure is 7.5 × 10 at 650 deg.C ^-7 The equilibrium vapor pressure of Torr and silicon beam is 3.0 x 10 ^-8 Growing a GaN epitaxial layer with a thickness of 100nm and a doping concentration of 5 × 10 under process conditions of Torr, a nitrogen flow of 2.3sccm, and a nitrogen plasma radio frequency source power of 375W ¹⁹ cm ^-3 First layer n of ⁺ A GaN series layer.

C.3 In the first layer n) ⁺ Growing a second active layer on the GaN series layerZone, fig. 6 (c), the specific implementation of this step is the same as step (c.1);

c.4 A second layer n) is grown on the second layer active region ⁺ GaN tandem layer, fig. 6 (d), the specific implementation of this step is the same as step (c.2);

c.5 In the second layer n) ⁺ Growing a third active region on the GaN series layer, as shown in FIG. 6 (e), wherein the specific implementation of this step is the same as that of step (C.1);

c.6 Growth of a third layer n on the third layer active region ⁺ GaN series layer, as in fig. 6 (f). The concrete realization of the step is the same as that of the step (C.2);

c.7 In the third layer n) ⁺ Growing a fourth active region on the GaN series layer, as shown in FIG. 6 (g), wherein the specific implementation of this step is the same as that of step (C.1);

c.8 Grow a fourth layer n on the fourth layer active region ⁺ GaN tandem layer, fig. 6 (h), the specific implementation of this step is the same as step (c.2).

C.9 In the fourth layer n) ⁺ And (5) growing a fifth layer active region on the GaN series layer, as shown in FIG. 6 (i), wherein the specific implementation of the step is the same as that of the step (C.1).

C.6 Growth of a fifth layer n on the fifth layer active region ⁺ GaN tandem layer, fig. 6 (j), the specific implementation of this step is the same as step (c.2).

C.7 In the fifth layer n) ⁺ Growing a sixth active region on the GaN series layer, as shown in fig. 6 (k), wherein the specific implementation of this step is the same as that of step (c.1); completing six active regions and five n layers ⁺ And growing a composite active region with the GaN series layers arranged alternately.

Step D, growing n ⁺ And a GaN collector ohmic contact layer.

Adopting molecular beam epitaxy method, at 650 deg.C, nitrogen flow of 2.3sccm, and gallium beam balance vapor pressure of 7.5 × 10 ^-7 The equilibrium vapor pressure of Torr and silicon beam is 3.0 x 10 ^-8 Growing the layer six active region with the thickness of 300nm and the doping concentration of 5 multiplied by 10 under the process condition that the power of a Torr and a nitrogen plasma radio frequency source is 375W ¹⁹ cm ^-3 N of (a) ⁺ And the GaN collector ohmic contact layer.

Step E, at n ⁺ And photoresist is homogenized, photoetching, developing and etching are carried out on the GaN collector ohmic contact layer to form a grid-shaped mesa isolation with the depth of 1000 nm.

E.1 Photolithography is used to form mesa isolation patterns:

the specific implementation of this step is the same as step 5.1) of example one.

E.2 Etching to form mesa isolation:

using photoresist as mask, adopting inductively coupled plasma etching method, and using Cl ₂ The gas flow rate was 10sccm, BCl ₃ Etching n under the process conditions of the gas flow of 25sccm and the etching time of 500s ⁺ The GaN collector ohmic contact layer forms a grid-shaped mesa isolation with the depth of 1000 nm.

Step F, at n ⁺ Etching the GaN collector ohmic contact layer to n ⁺ And forming a cylindrical table top with the diameter of 4 mu m by using the GaN emitter ohmic contact layer, and depositing metal to form a collector electrode.

F.1 Lithography to form a circular mesa pattern:

f.1.1 In n) ⁺ Spin coating PMMA A4 photoresist on the InN collector ohmic contact layer: firstly, the rotation speed is 500rad/min, the acceleration is 1000rad ² Spin coating for 3s at min; then the rotation speed is 4000rad/min, the acceleration is 2000rad ² Spin coating for 30s at min, and baking at 180 deg.C for 90s.

F.1.2 Adopting an electron beam lithography method, setting the electron dose ratio to be 750, and carrying out exposure treatment on the PMMA A4 photoresist;

f.1.3 For the photoresist after exposure treatment, the ratio of 3:1 and an isopropyl alcohol solution, developing for 120s, and fixing for 30s with isopropyl alcohol to form a circular mesa pattern with a diameter of 4 μm.

F.2 By electron beam evaporation on a circular mesa pattern

f.3 Using inductively coupled plasma with metal as a maskMethod of bulk etching, setting Cl ₂ The gas flow rate was 10sccm, BCl ₃ The gas flow is 25sccm, the etching time is 150s, and n is etched ⁺ InN collector ohmic contact layer to n ⁺ And the GaN emitter ohmic contact layer forms a cylindrical mesa with the diameter of 4 mu m.

Step G, at n ⁺ And a ring-shaped emitter electrode with the inner circumference being 3 mu m away from the cylindrical table top is formed on the GaN emitter ohmic contact layer.

Step H, depositing HfO ₂ A dielectric passivation layer.

An atomic layer deposition process is used, the set time is 70s, the temperature is 280 ℃, the flow of ethyl methylamino hafnium is 1200sccm ₂ The O flow is 110sccm, N ₂ The flow rate is 1000sccm, and HfO with the thickness of 100nm is deposited on the whole surface of the device ₂ A dielectric passivation layer.

Step I, in HfO ₂ And photoetching and etching the dielectric passivation layer to form an emitter electrode through hole.

I.1 ) forming a pattern of emitter electrode through holes by photolithography, which is implemented in the same manner as in step 9.1) of the first embodiment.

I.2 Using the photoresist as a mask, set a pressure of 1500mTorr and a power of 200W ₆ Flow rate of 8sccm, CHF ₃ Etching HfO by using a reactive ion etching method at a flow rate of 10sccm and a flow rate of 150sccm for He ₂ And (4) a medium passivation layer reaches the metal surface of the emitter electrode to form an emitter electrode through hole.

Step J, in HfO ₂ A collector electrode through-hole having a diameter of 3 μm was prepared on the dielectric passivation layer, as shown in FIG. 3 (l).

J.1 ) a collector electrode via hole pattern is formed by photolithography, which is implemented in the same manner as in step 10 a) of the first embodiment.

J.2 Using the photoresist as a mask, set a pressure of 1500mTorr and a power of 200W ₆ Flow rate of 8sccm, CHF ₃ Etching HfO by reactive ion etching under the process conditions of 10sccm and 150sccm of He flow ₂ Passivating the dielectric layer to the metal surface of the collector electrode to form a collector with a diameter of 3 μmAnd an electrode through hole.

And step K, leading out an emitter electrode Pad and a collector electrode Pad on the through holes of the emitter electrode and the collector electrode, as shown in figure 3 (m).

The GaN epitaxial layer grown in the material epitaxy step of the three embodiments can be realized by adopting a metal organic chemical vapor deposition technology besides a molecular beam epitaxy method, and three embodiments for growing the GaN epitaxial layer by using the metal organic chemical vapor deposition technology are given below; in addition, the subsequent epitaxy steps of other materials are all the same as the three embodiments of the molecular beam epitaxy method.

Example IV production of a boron nitride substrate with Sc _0.18 Al _0.82 And the N barrier layer and the GaN quantum well are ScAlN/GaN two-region differential negative resistance gallium nitride-based resonant tunneling diodes.

Firstly, using a metal organic chemical vapor deposition method, setting the process conditions of 1000 ℃ of temperature, 40Torr of pressure, 1000sccm of ammonia gas flow, 60sccm of gallium source flow and 2000sccm of hydrogen flow, and growing a GaN epitaxial layer with the thickness of 500nm on a boron nitride substrate;

the specific implementation of other subsequent steps is the same as that of the step one.

Example V fabrication on a Diamond substrate Using Y _0.20 Al _0.80 The GaN-based resonant tunneling diode comprises an N barrier layer and an InGaN quantum well, wherein the YAlN/InGaN four-region differential negative resistance characteristic of the InGaN barrier layer and the InGaN quantum well is formed.

Step 1, using a metal organic chemical vapor deposition method, growing a GaN epitaxial layer with the thickness of 5000nm on a diamond substrate under the process conditions that the temperature is 1300 ℃, the pressure is 60Torr, the flow of ammonia gas is 3000sccm, the flow of a gallium source is 120sccm, and the flow of hydrogen is 5000 sccm.

The concrete implementation of other subsequent steps is the same as that of the corresponding step of the second example.

EXAMPLE six fabrication of a free-standing aluminum nitride Single Crystal substrate Using Y _0.20 Al _0.80 N potentialThe barrier layer and the InGaN quantum well are provided with a gallium nitride-based resonant tunneling diode with YAlN/InGaN four-region differential negative resistance characteristics.

Step A, using a metal organic chemical vapor deposition method, growing a GaN epitaxial layer with the thickness of 2000nm on a self-supporting aluminum nitride single crystal substrate under the process conditions that the temperature is 1100 ℃, the pressure is 50Torr, the ammonia gas flow is 2000sccm, the gallium source flow is 90sccm, and the hydrogen gas flow is 3000 sccm.

The specific implementation of other subsequent steps is the same as that of the corresponding step of the third example.

The effects of the present invention can be further illustrated by the following test results:

in the first embodiment, a gan-based resonant tunneling diode based on the differential negative resistance characteristic of two regions on a self-supporting gan substrate was measured to obtain an I-V dc characteristic curve, as shown in fig. 7.

From fig. 7, the following conclusions can be drawn:

first, the present example consists of 2 layers of active regions and 1 layer of n ⁺ The double-layer composite structure active region formed by the GaN series layers can realize the differential negative resistance characteristic of two regions by using a single device through the resonance tunneling phenomenon of each active region, thereby saving the wafer area, having high device integration level, avoiding the metal interconnection of the on-chip device integration process, having simple preparation process and improved fault tolerance rate;

second, this example is due to its 2-layer active region and 1-layer n ⁺ The GaN series layers are all realized in the epitaxial direction, so that the consistency of the thickness of epitaxial materials is ensured, and the survival rate and the reliability of devices are improved;

thirdly, the present embodiment uses 1 layer n ⁺ The GaN series layer is communicated with the 2 layers of active regions in the vertical direction, the self-excited oscillation frequency of the differential negative resistance region of the resonant tunneling diode can be changed by adjusting the thickness and the doping concentration of the series layer, the chair-shaped bulge of the output characteristic curve is eliminated, and the stability and the reliability of the device are improved

As can be seen from the above results of measuring the gallium nitride-based resonant tunneling diode with two-region differential negative resistance, the gallium nitride-based resonant tunneling diode with multi-region differential negative resistance of the multi-layer composite active region structure having more than two active regions has a better effect than the first embodiment.

Claims

1. A gallium nitride-based resonant tunneling diode with a multi-region differential negative resistance effect comprises a substrate (1), a GaN epitaxial layer (2), an emitter ohmic contact layer (3), an active region (4), a collector ohmic contact layer (5), a collector electrode (6) and annular emitter electrodes (8) arranged on two sides of the active region from bottom to top; active region (4) to collecting electrode (6) are the cylinder mesa that the sculpture formed, and this cylinder mesa outside parcel has passivation layer (7), its characterized in that:

the active region (4) is composed of N layers of active regions and N-1 layers of N ⁺ The GaN series layers are arranged alternately to form a composite structure, and the doping concentration between each two active regions is 1 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 30nm to 200nm ⁺ The GaN series connection layer is connected to realize differential negative resistance characteristics with a plurality of peak current and peak-to-valley current ratios close to each other, wherein N is more than or equal to 2.

2. The diode of claim 1, wherein: each layer of the active region (4) of the composite structure comprises a first isolation layer (41), a first barrier layer (42), a quantum well layer (43), a second barrier layer (44) and a second isolation layer (45) from bottom to top;

the thickness of the first isolation layer (41) and the thickness of the second isolation layer (45) are both GaN of 4nm-15 nm;

the first barrier layer (42) and the second barrier layer (44) have the same composition, the thickness of the first barrier layer and the second barrier layer is 1nm-3nm, and the thicknesses of the first barrier layer and the second barrier layer are the same;

the quantum well layer (43) employs In having a composition v between 0% and 100% _v Ga _1-v N with the thickness of 1nm-3nm.

3. The diode of claim 2, wherein: the first barrier layer (42) and the second barrier layer (44) are made of the same material, and both can adopt Sc _x Al _1-x N、Y _x Al _1-x N、B _w Al _y Ga _z And N, wherein the component x is between 5 and 25 percent, the components w, y and z are between 0 and 100 percent, and the w + y + z =100 percent.

4. The diode of claim 1, wherein:

the collector ohmic contact layer (5) has a doping concentration of 5 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 50nm to 200nm ⁺ GaN；

The ohmic contact layer (3) of the emitter has the doping concentration of 5 multiplied by 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 N with a thickness of 50nm to 200nm ⁺ GaN；

The thickness of the GaN epitaxial layer (2) is 500nm-5000nm.

5. The diode of claim 1, wherein:

the passivation layer (7) is made of SiN material and Al ₂ O ₃ Material, hfO ₂ Any one of the materials;

the substrate (1) is made of any one of a self-supporting gallium nitride single crystal material, a self-supporting aluminum nitride single crystal material, a sapphire material, a silicon carbide material, a silicon material, a boron nitride material and a diamond material.

6. A method for manufacturing a gallium nitride-based resonant tunneling diode with a multi-differential negative resistance effect is characterized by comprising the following steps:

1) A GaN epitaxial layer (2) with the thickness of 500nm-5000nm is epitaxially grown on the substrate (1) by adopting a molecular beam epitaxy method or a metal organic chemical vapor deposition method;

2) Growing n on the GaN epitaxial layer (2) by molecular beam epitaxy ⁺ A GaN emitter ohmic contact layer (3) with a thickness of 50nm-200nm and a doping concentration of 5 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 ；

3) By molecular beam epitaxy method at n ⁺ Multiple alternative growths on the GaN emitter ohmic contact layer (3)Active region (4) of the layer composite structure:

3a) Growing a first layer of active region:

3a1) At n ⁺ A GaN first isolating layer (41) with the thickness of 4nm-15nm is grown on the GaN emitting electrode ohmic contact layer (3);

3a2) Growing Sc with the thickness of 1nm-3nm and the component x between 5% and 25% on the GaN first isolation layer (41) _x Al _1-x N or Y _x Al _1-x N; or the components w, y and z are 0-100%, w + y + z =100%, and the thickness is 1nm-3nm of B _w Al _y Ga _z A first barrier layer (42) of N;

3a3) Growing In with a composition v between 0% and 100% and a thickness of 1nm to 3nm on the first barrier layer (42) _v Ga _1-v An N quantum well layer (43);

3a4) Growing a second barrier layer (44) having the same composition and thickness as the first barrier layer (42) on the quantum well layer (43);

3a5) Growing a GaN second isolation layer (45) with the thickness of 4nm-15nm on the second barrier layer (44) to finish the growth of the first layer active region;

3b) Growing a doping concentration of 1 × 10 on the first active region by molecular beam epitaxy ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 A first layer n having a thickness of 30nm to 200nm ⁺ A GaN series layer;

3c) In the first layer n ⁺ Generating a second active region on the GaN series layer according to the process flow of 3 a), and finishing the growth of the active region with a composite structure of two active regions and one series layer; sequentially and circularly growing to finally form the active region with N layers and N-1 layers of N ⁺ An active region (4) of a multilayer composite structure of GaN series layers;

4) Growing n on the active region (4) of the composite structure by molecular beam epitaxy ⁺ A GaN collector ohmic contact layer (5) with a thickness of 50nm-200nm and a doping concentration of 5 × 10 ¹⁹ cm ^-3 -5×10 ²⁰ cm ^-3 ；

5) Using conventional optical lithography process, at n ⁺ Forming a device mesa isolation pattern on the GaN collector ohmic contact layer (5), and adopting inductive coupling plasma with the photoresist as a maskDaughter etching method using BCl ₃ /Cl ₂ A gas source for etching the epitaxial material to form a mesa isolation with a depth of 650nm-1200 nm;

6) Using electron beam lithography at n ⁺ A round pattern with the diameter of 0.5-20 μm is formed on the GaN collector ohmic contact layer (5), and the photoresist is used as a mask to perform electron beam evaporation on n ⁺ Evaporating a Ti/Au/Ni metal layer on the GaN collector ohmic contact layer (5) to form a collector electrode (6), and then using the metal as a mask, adopting an inductively coupled plasma etching method and using BCl ₃ /Cl ₂ Gas source, etching depth to n ⁺ A GaN emitter ohmic contact layer (3) forming a cylindrical mesa from the first active layer to the collector electrode (6);

7) Using conventional optical lithography process, at n ⁺ Forming a ring pattern with an inner circumference distance of 3 μm from the cylindrical table top on the GaN emitter ohmic contact layer (3), and evaporating n by electron beam evaporation with photoresist as mask ⁺ Evaporating a Ti/Au metal layer on the GaN emitter ohmic contact layer (3) to form an emitter electrode (8);

8) Using plasma enhanced chemical vapor deposition or atomic layer deposition process at n ⁺ A passivation layer (7) with the thickness of 50nm-200nm is deposited from the GaN emitter ohmic contact layer (3) to the surface of the collector electrode (6);

9) And forming an emitter electrode through hole pattern on the passivation layer (7) by adopting a traditional optical photoetching process. Using photoresist as mask, adopting reactive ion etching method, using SF ₆ A gas source forming an emitter electrode through hole;

10 Using an electron beam lithography process to form a circular pattern having a diameter of 200nm-18 μm on the passivation layer of the cylindrical mesa. Using photoresist as mask, adopting reactive ion etching method, and using SF ₆ A gas source forming a collector electrode through hole;

7. The method of manufacturing of claim 6, wherein:

the metal organic chemical vapor deposition method adopted in the step 1) comprises the following process conditions:

the temperature is 1000-1300 ℃, the pressure is 40-60 Torr, the flow of ammonia gas is 1000-3000 sccm, the flow of gallium source is 60-120 sccm, and the flow of hydrogen is 2000-5000 sccm;

the molecular beam epitaxy method adopted in the step 1) comprises the following process conditions: the temperature is 650-720 ℃, the equilibrium vapor pressure of the gallium beam is 4.5 multiplied by 10 ^-7 Torr-8.5×10 ^-7 The nitrogen flow is 1.2sccm to 2.3sccm, and the nitrogen plasma RF source power is 375W.

8. The method of manufacturing of claim 6, wherein:

the molecular beam epitaxy method in the step 2) and the step 4) has the following process conditions: the temperature is 650-720 ℃, the equilibrium vapor pressure of the gallium beam is 4.5 multiplied by 10 ^-7 Torr-8.5×10 ^-7 Torr, equilibrium vapor pressure of silicon beam current is 2.5X 10 ^-8 Torr-4.5×10 ^-8 The nitrogen flow is 1.2sccm-2.3sccm, and the nitrogen plasma radio frequency source power is 375W;

the molecular beam epitaxy method in the step 3) has the following process conditions: the temperature is 500-720 ℃, the nitrogen flow is 1.2-2.3 sccm, the gallium beam balance vapor pressure is 4.5 multiplied by 10 ^-7 Torr-8.5×10 ^-7 Torr, the equilibrium vapor pressure of aluminum beam is 1.4X 10 ^-7 Torr-3.2×10 ^-7 Torr, equilibrium vapor pressure of indium beam current is 1.4X 10 ^-7 Torr-3.2×10 ^-7 Torr, equilibrium vapor pressure of boron beam is 2.0X 10 ^-7 Torr-4.0×10 ^-7 Torr, scandium Beam equilibrium vapor pressure of 1.5X 10 ^-8 Torr-1.8×10 ^-8 Torr, the equilibrium vapor pressure of yttrium beam is 1.0X 10 ^-8 Torr-2.0×10 ^-8 Torr, equilibrium vapor pressure of silicon beam current is 2.0X 10 ^-8 Torr-4.5×10 ^-8 Torr, nitrogen plasma RF source power was 375W.

9. The method of manufacturing of claim 6, wherein:

the conventional optical lithography process in the step 5) has the following process conditions: using AZ5214 photoresist, firstly rotating at 500rad/min and accelerating at 1000rad ² Spin coating for 3s at min; then the rotation speed is 4000rad/min, the acceleration is 2000rad ² Spin coating for 30s at/min. Drying the glue for 90s at the temperature of 95 ℃; the developer adopts RZX-3038, and the developing time is 45s.

The plasma enhanced chemical vapor deposition method adopted in the step 5) has the following process conditions: at a pressure of 2200mTorr and a temperature of 350 deg.C SiH ₄ The flow rate was 13.5sccm ₃ The flow rate was 10sccm, N ₂ The flow rate is 1000sccm and the time is 30-120 s.

The process conditions of the inductively coupled plasma etching method in the step 5) are as follows: cl ₂ The gas flow rate was 10sccm, BCl ₃ The gas flow is 25sccm, and the etching time is 300-420 s.

10. The method of manufacturing of claim 6, wherein: the electron beam lithography process adopted in the step 6) has the process conditions that:

adopting PMMA A4 photoresist, wherein the photoresist drying time is 90s, the temperature is 180 ℃, the electron dose ratio is 750, the diameter of a photoetching circular pattern is 1-4 mu m, and the developing agent is 3:1, tetramethylcyclopentanone and isopropanol, the developing time is 120s; the fixer was isopropyl alcohol and the fixing time was 30s.