CN102427085A

CN102427085A - Group III nitride enhancement mode HEMT (High Electron Mobility Transistor) device

Info

Publication number: CN102427085A
Application number: CN2011103669926A
Authority: CN
Inventors: 蔡勇; 于国浩; 董志华; 王越; 张宝顺
Original assignee: Suzhou Institute of Nano Tech and Nano Bionics of CAS
Current assignee: Suzhou Institute of Nano Tech and Nano Bionics of CAS
Priority date: 2011-11-18
Filing date: 2011-11-18
Publication date: 2012-04-25
Anticipated expiration: 2031-11-18
Also published as: CN102427085B

Abstract

The invention discloses a group III nitride enhancement mode HEMT (High Electron Mobility Transistor) device which comprises source and drain electrodes, main and accessory grids, an insulating medium layer and a heterostructure, wherein the source and drain electrodes are electrically connected by two-dimensional electron formed in the heterostructure; the heterostructure comprises a first semiconductor and a second semiconductor; the first semiconductor is arranged between the source and drain electrodes; the second semiconductor is formed on the surface of the first semiconductor and is provided with a band gap which is wider than the first semiconductor; the main grid is arranged at one side of the surface of the second semiconductor near the source electrode and forms schottky contact with the second semiconductor, and a plasma processing area is also formed in the local area of the second semiconductor under the main grid; a medium layer is formed on the surfaces of the second semiconductor and the main grid and between the source and drain electrodes; and the accessory grid is formed on the surface of the medium layer, the edge of at least one side of the accessory grid extends to the direction of the source electrode or drain electrode, and the orthographic projection of the accessory grid is laminated with the edges of both sides of the main grid. The group III nitride enhancement mode HEMT device can effectively inhibit the current collapse effect fundamentally.

Description

III group-III nitride enhancement mode HEMT device

Technical field

The present invention relates to a kind of enhancement type high electron mobility transistor (Enhancement-mode High Electron Mobility Transistor, E-mode HEMT), relate in particular to a kind of III group-III nitride enhancement mode HEMT device.

Background technology

When the HEMT device adopts the III group-III nitride semiconductor, because piezoelectric polarization and spontaneous polarization effect on heterostructure (Heterostructure), like AlGaN/GaN, can form the two-dimensional electron gas of high concentration.In addition, the HEMT device adopts the III group-III nitride semiconductor, can obtain very high insulation breakdown electric field strength and good high-temperature stability.HEMT with III group-III nitride semiconductor of heterostructure not only can be used as high-frequency element and uses, and is applicable to the device for power switching of high voltage, big electric current.When being applied in the high-power switching circuit, consider that generally requiring switching device to have normal pass characteristic, promptly to need device be enhancement device (E-MODE) for the simplicity of design of circuit and secure context.

When existing III group-III nitride semiconductor E-MODE HEMT device uses as high-frequency element or high voltage switch device; The drain electrode output current does not often catch up with the variation of grid control signal; The big situation of conducting transient delay can appear; " the current collapse phenomenon " that this is III group-III nitride semiconductor E-MODE HEMT device having a strong impact on the practicality of device.Existing explanation to " current collapse phenomenon " of relatively generally acknowledging is " an empty bar phantom "." empty bar phantom " think when device closes off-state, have electronics to be injected into semiconductor surface, thereby formed electronegative empty grid by surface state or defect capture; Electronegative empty grid are because the electrostatic induction meeting reduces the channel electrons of grid leak, bonding pad, grid source; When device changed from closing off-state guide on-state, though the raceway groove under the grid can accumulate a large amount of electronics very soon, empty grid electric charge but can not in time discharge; Channel electrons concentration under the empty grid is lower; So the drain terminal output current is less, have only after empty grid electric charge fully discharges, the drain terminal electric current just can return to the level of dc state.At present, the method for inhibition " current collapse " commonly used has: semiconductor is carried out surface treatment, reduce surface state or interface state density; Reduce the electric field strength of gate electrode through field plate structure, reduce electronics, suppress current collapse by the probability of surface state and defect capture near drain electrode one end.But the method for aforementioned inhibition current collapse effect under big electric current, big voltage condition is unsatisfactory.

Summary of the invention

The objective of the invention is to propose a kind of III group-III nitride E-MODE HEMT device; This device has the lamination double-gate structure; Be through the enhancement device of plasma to the processing realization of grid lower area; It is regulated and control two-dimensional electron gas in the raceway groove by cooperatively interacting of secondary grid and main grid; Make E-MODE HEMT (Enhancement-mode High Electron Mobility Transistor, enhancement type high electron mobility transistor) drain terminal output current can get caught up in the variation of gate voltage, thereby fundamentally suppressing " current collapse effect ".

For realizing the foregoing invention purpose, the present invention has adopted following technical scheme:

A kind of III group-III nitride E-MODE HEMT device; Comprise source electrode, drain electrode and heterostructure, said source electrode is electrically connected through the two-dimensional electron gas that is formed in the heterostructure with drain electrode, and said heterostructure comprises first semiconductor and second semiconductor; Said first semiconductor is arranged between source electrode and the drain electrode; Said second semiconductor is formed at first semiconductor surface, and has and be wider than the first semi-conductive band gap, it is characterized in that; Said E-MODE HEMT device also comprises main grid, insulating medium layer and secondary grid, wherein:

Said main grid is arranged at second semiconductor surface near source electrode one side, and contacts with second semiconductor formation Xiao Jite, and the second semiconductor regional area inside that is positioned at below the main grid also is formed with the Cement Composite Treated by Plasma district;

Said dielectric layer is formed at second semiconductor and main grid surface, and is arranged between said source electrode and the drain electrode;

Said secondary grid are formed at the dielectric layer surface, and its at least one lateral edges extends to source electrode or drain electrode direction, and its orthographic projection simultaneously and main grid both sides of the edge all overlap.

Said source electrode is connected with high potential with the electronegative potential of power supply respectively with drain electrode.

Preferably, said Cement Composite Treated by Plasma district is the regional area formed electronegative fixed charge district after F (fluorine) Cement Composite Treated by Plasma in second semiconductor.

Saying further; Said Cement Composite Treated by Plasma district carries out the F Cement Composite Treated by Plasma through reactive ion etching (RIE) or inductively coupled plasma etching technologies such as (ICP) to heterojunction; Thereby in second semiconductor, form electronegative fixed charge district, and two-dimensional electron gas in its pairing raceway groove is exhausted.

Said first semiconductor and second semiconductor equalizing adopt the III group-III nitride semiconductor.

Extend to source electrode and drain electrode direction respectively the both sides of the edge of said secondary grid, perhaps, also can be that said secondary grid only have a lateral edges to extend to corresponding source electrode or drain electrode direction.

When said HEMT device was worked, said main grid and secondary grid were respectively by control signal control, and when said HEMT device was handled conducting state, the current potential of said secondary grid-control system signal was higher than the current potential of main grid control signal.

Description of drawings

Fig. 1 is the cross-sectional view of lamination double grid E-MODE HEMT of the present invention;

Fig. 2 a is the partial structurtes sketch map of common E-MODE HEMT device;

Fig. 2 b is the partial structurtes sketch map of lamination double grid E-MODE HEMT device of the present invention;

Fig. 3 is the structural representation of E-MODE HEMT device in the present invention's one preferred embodiments, and wherein secondary grid respectively have extension to leakage and source electrode direction;

Fig. 4 is the structural representation of E-MODE HEMT device in another preferred embodiments of the present invention, and wherein secondary grid only have extension to the drain electrode direction.

Embodiment

Consult Fig. 2 a; The reason of common E-MODE HEMT device (is example with the AlGaN/GaN device) current collapse phenomenon is: under the device off state; Can accumulate negative electrical charge at grid metal 4 both sides AlGaN layers 3 at the interface with dielectric 7, form interface negative electrical charge accumulation area 21, because the electrostatic induction effect; These negative electrical charges can reduce even exhaust fully the two-dimensional electron gas of below channel region again, form raceway groove depletion region 22.When the grid voltage rising, when device was changed from closing off-state guide on-state, grid below two-dimensional electron gas received grid voltage control and rises; Grid below turn, but the negative electrical charge of interface charge accumulation area is owing to be in than deep energy level and can not in time disengage, and therefore the two-dimensional electron gas in the raceway groove of below still is less; So device conducting fully, along with the time increases, the negative electrical charge of interface charge accumulation area discharges from deep energy level gradually; Electron concentration rises in its below raceway groove; Device changes to complete conducting gradually, and according to present result of study, negative electrical charge reaches the magnitude of microsecond～second from the time that deep energy level discharges.

For overcoming the defective of aforementioned common E-MODE HEMT device, the present invention proposes a kind of III group-III nitride E-MODE HEMT device with lamination double-gate structure, consult Fig. 1; Source electrode 8, the drain electrode 9 of this device are positioned at both sides; One gate electrode being arranged, be called main grid 4 near second semiconductor 3 of source electrode 8 one sides (like, AlGaN layer) surface; There is a fixed negative charge district 6 through Cement Composite Treated by Plasma the main grid below; There is an insulating medium layer 7 the main grid top, and there is another gate electrode the insulating medium layer top, is called secondary grid 5.As shown in Figure 1, secondary grid are positioned at the top of main grid, on vertical plane, with the main grid both sides of the edge overlapping are arranged, and to source, drain electrode certain extension are arranged.Aforementioned first semiconductor 2 (like the GaN layer) can be located on the substrate 1.

Consult Fig. 2 b; Under lamination double grid E-MODE HEMT device off state of the present invention; Main grid is biased in below the threshold voltage, adds a sufficiently high positive bias on the secondary grid 5 ', though main grid 4 ' metal both sides, second semiconductor layer and dielectric can accumulate negative electrical charge at the interface equally; Because sufficiently high forward biased effect on the secondary grid; The interface negative electrical charge can not shield secondary grid electric field fully, has enough electric fields two-dimensional electron gas in the channel region that goes to induct, and keeps raceway groove 23 conductings of electric charge accumulating region below; When the rising of main grid voltage, when device changed from closing off-state guide on-state, secondary gate voltage remained unchanged, the still conducting of raceway groove of interface charge accumulation area below, so device can not produce the delay that current collapse causes.

And if device works in on-off mode; The type of drive of lamination double grid E-MODE HEMT device then of the present invention can be taked: main grid and secondary grid are added synchronous pulse signal respectively; Secondary gate voltage is higher than main grid voltage; When device changed from closing the logical shape of off-state guide, the high voltage of secondary grid can overcome the shielding of interface negative electrical charge and thereunder force to generate enough two-dimensional electron gas, has avoided current collapse.It should be noted that the biasing of secondary grid can be independent of main grid when closing off-state, therefore select the biasing of secondary grid under the suitable pass off-state, device can obtain preferable puncture voltage.

More than technical scheme of the present invention is summarized; For can more being known, the public understands technological means of the present invention; And can implement according to the content of specification, below be that example is further described technical scheme of the present invention with device based on the AlGaN/GaN heterojunction.

Consult Fig. 3, as a kind of preferred embodiments of the present invention, this E-MODE HEMT has: first semiconductor 13 (GaN) and be formed on second semiconductor 14 (AlGaN) on first semiconductor 13.First semiconductor 13 specially mixes.In second semiconductor 14, can mix n type impurity, also can not mix.The band gap of second semiconductor 14 is wideer than the band gap of first semiconductor 13.The thickness of second semiconductor 14 is about 15 to 30nm.First semiconductor 13 and second semiconductor 14 form heterostructure, are forming two-dimensional electron gas (2DEG) at the interface.

This E-MODE HEMT has by the drain electrode 11 and source electrode 12 of predetermined distance apart from configured separate.Drain electrode 11 runs through second semiconductor 14 with source electrode 12 and extends to first semiconductor 13, is connected with two-dimensional electron gas in the raceway groove.Drain electrode 11 is to form ohmic contact by multiple layer metal (as: Ti/Al/Ti/Au or Ti/Al/Ni/Au etc.) through quick high-temp annealing with source electrode 12.

This E-MODE HEMT has Cement Composite Treated by Plasma district 19, and it is the fixed negative charge district that below second semiconductor inside, main grid, forms through Cement Composite Treated by Plasma, can the two-dimensional electron gas in its pairing raceway groove be exhausted.

This E-MODE HEMT has major and minor double-gate structure, and main grid 16 is manufactured between source electrode and the drain electrode, and near an end of source electrode, main grid 16 directly contacts with second semiconductor, 14 surfaces, and forms Schottky contacts.Secondary grid 18 are arranged on dielectric layer 17 (like Si ₃N ₄) on, with main grid overlapping is arranged in vertical direction, and extension (perhaps only extend to drain electrode or source electrode direction, shown in Figure 4 is the structure that secondary grid only extend to the drain electrode direction) is respectively arranged to source, drain electrode direction.

Claims

1. III group-III nitride enhancement mode HEMT device; Comprise source electrode, drain electrode and heterostructure, said source electrode is electrically connected through the two-dimensional electron gas that is formed in the heterostructure with drain electrode, and said heterostructure comprises first semiconductor and second semiconductor; Said first semiconductor is arranged between source electrode and the drain electrode; Said second semiconductor is formed at first semiconductor surface, and has and be wider than the first semi-conductive band gap, it is characterized in that; Said HEMT device also comprises main grid, insulating medium layer and secondary grid, wherein:

2. III group-III nitride enhancement mode HEMT device according to claim 1 is characterized in that said source electrode is connected with high potential with the electronegative potential of power supply respectively with drain electrode.

3. III group-III nitride enhancement mode HEMT device according to claim 1 is characterized in that, said Cement Composite Treated by Plasma district is the regional area formed electronegative fixed charge district after fluoro plasma is handled in second semiconductor.

4. III group-III nitride enhancement mode HEMT device according to claim 1 is characterized in that, said first semiconductor and second semiconductor equalizing adopt the III group-III nitride semiconductor.

5. III group-III nitride enhancement mode HEMT device according to claim 1 is characterized in that, extend to source electrode and drain electrode direction respectively the both sides of the edge of said secondary grid.

6. III group-III nitride enhancement mode HEMT device according to claim 1 is characterized in that, said secondary grid only have a lateral edges to extend to corresponding source electrode or drain electrode direction.

7. III group-III nitride enhancement mode HEMT device according to claim 1; It is characterized in that; When said HEMT device is worked; Said main grid and secondary grid are respectively by control signal control, and when said HEMT device was in conducting state, the current potential of said secondary grid-control system signal was higher than the current potential of main grid control signal.