There is the gallium nitride radical heterojunction field effect pipe of composite field plate structure in body
Technical field
The present invention relates to semiconductor technology, particularly gallium nitride (GaN) radical heterojunction field effect transistor strain n channel metal oxide semiconductor field effect transistor (NMOSFET).
Background technology
Gallium nitride (GaN) radical heterojunction field effect transistor (HFET) has that energy gap is large, critical breakdown electric field is high, electron saturation velocities is high, the excellent specific property such as good heat conductivity, radioresistance and good chemical stability, simultaneously gallium nitride material can form the two-dimensional electron gas heterojunction raceway groove with high concentration and high mobility with the material such as aluminum gallium nitride (AlGaN), therefore being specially adapted to high pressure, high-power and high temperature application, is one of transistor of applied power electronics most potentiality.
Fig. 1 is prior art common GaN HFET (gallium nitride radical heterojunction field effect transistor) structural representation, mainly comprise substrate 107, gallium nitride (GaN) resilient coating 106, gallium nitride (GaN) channel layer 105, the source electrode 101 that aluminum gallium nitride (AlGaN) barrier layer 104 and aluminum gallium nitride (AlGaN) barrier layer 104 are formed, drain electrode 102 and grid 103, wherein nitride buffer layer 106 is arranged on above substrate 107, gallium nitride channel layer 105 is arranged on above nitride buffer layer 106, aluminum gallium nitride barrier layer 104 is arranged on above gallium nitride channel layer 105, source electrode 101 and drain electrode 102 form ohmic contact with aluminum gallium nitride (AlGaN) barrier layer 104, grid 103 and aluminum gallium nitride (AlGaN) barrier layer 104 form Schottky contacts.But for common GaN HFET, when device bears withstand voltage, because raceway groove two-dimensional electron gas can not exhaust completely between grid 103 and drain electrode 102, make raceway groove electric field mainly concentrate on grid 103 edge, cause device just breakdown under lower drain voltage.Drain electrode 102 can be arrived through GaN resilient coating from source electrode injected electrons simultaneously, form leak channel, excessive resilient coating leakage current can cause device to puncture in advance equally, cannot give full play to the withstand voltage advantage of height of GaN material, thus the application of restriction GaN HFET in high pressure.
In order to make Electric Field Distribution between grid 103 and drain electrode 102 more even in prior art, suppressing resilient coating leakage current, improving device electric breakdown strength, usually adopt with the following method:
Use surface field plate technique [D.Vislalli et al., " Limitations of Field Plate Effect Due to the Silicon Substrate in AlGaN/GaN/AlGaN DHFETs ", IEEE Trans.Electron Devices, Vol.57, No.12, p.3333-3339 (3060)].Field plate structure can exhaust the raceway groove two-dimensional electron gas under it effectively, the Two-dimensional electron depleted region between extended grid and drain electrode, makes the Electric Field Distribution between grid leak more even, thus reaches the object improving puncture voltage.But field plate structure still cannot exhaust the raceway groove two-dimensional electron gas between grid and drain electrode completely, resilient coating leakage current cannot be suppressed simultaneously, the withstand voltage advantage of GaN material can not be given full play to.
The impurity such as carbon, iron [Eldad Bahat-Treidel et al. is mixed in resilient coating, " AlGaN/GaN/GaN:C Back-Barrier HFETs With Breakdown Voltage of Over 1kV and Low RON × A ", Trans.on Electron Devices, Vol.57, No.11, p.3050-3058 (3060)].The impurity such as carbon, iron can introduce deep energy level electron trap in GaN resilient coating, captures from source electrode injected electrons, increases resilient coating resistance, is contributed to exhausting two-dimensional electron gas in raceway groove simultaneously, make device channel Electric Field Distribution more even by the trap of electrons occupy.But this technology can not exhaust the two-dimensional electron gas in raceway groove completely, the withstand voltage advantage of GaN material cannot be given full play to, the Deep Level Traps that simultaneously impurity such as carbon, iron is introduced can cause that such as conducting resistance increases, output current declines, degradation negative effect under current collapse effect and reaction speed.
The way (US 2006/0170003 A1) of the in-vivo metal electrode be connected with back electrode is directly introduced in p-type Si substrate.Though this technology is unrealized temporarily at present, but from theory analysis, metal electrode and semiconductor directly contact and can not reduce leakage current, on the contrary because of its good conductivity, more easily form resilient coating electric leakage raceway groove, thus reduce the puncture voltage of device.In addition, close together between this internal electrode and drain electrode, centre only also exists PN junction structure, and its reverse leakage is very large, if this internal electrode is connected with source electrode or grid, the voltage endurance capability of so whole device is only equivalent to common GaN PN junction.Except described in above 2 on except the impact of puncture voltage, this structure cannot allow the N-type channel doping of higher concentration to reduce conducting resistance, is therefore difficult to the figure of merit (FOM) of boost device.
Summary of the invention
The object of the invention is to overcome the withstand voltage not high shortcoming of current gallium nitride radical heterojunction field effect transistor, a kind of gallium nitride radical heterojunction field effect pipe with composite field plate structure in body is provided.
The present invention solves its technical problem, the technical scheme adopted is, there is the gallium nitride radical heterojunction field effect pipe of composite field plate structure in body, comprise substrate 107, nitride buffer layer 106, gallium nitride channel layer 105, aluminum gallium nitride barrier layer 104, source electrode 101, drain electrode 102 and grid 103, described nitride buffer layer 106 is arranged on above substrate 107, it is characterized in that, also comprise composite field plate structure in body, in described body, composite field plate structure is made up of electrode 208 and insulating medium layer 209, the horizontal level of described electrode 208 is between grid 103 and drain electrode 102, the lower surface of electrode 208 contacts with device lower surface, insulating medium layer 209 covers electrode 208 and is positioned at substrate 107, in nitride buffer layer 106 and gallium nitride channel layer 105 other on the surface, in body composite field plate structure vertical direction on thickness be less than the distance of upper surface to substrate 107 lower surface of gallium nitride channel layer 105.
Concrete, described electrode 208 is made up of metal or high doping semiconductor material.
Further, described insulating medium layer 209 is made up of silicon dioxide and/or aluminium oxide and/or silicon nitride and/or hafnium oxide.
Concrete, in described body, composite field plate structure width is in the horizontal direction less than the distance between grid 103 to drain electrode 102.
Further, the electricity connected mode of described electrode 208 is for being biased separately or being connected with source electrode 101 or being connected with grid 103 or being connected with drain electrode 102.
Concrete, described gallium nitride channel layer 105 is N-type doping, and doping content scope is 1 × 10
14cm
-3to 1 × 10
20cm
-3.
Further, described nitride buffer layer 106 has N-type doping content at insulating medium layer 209 near the part of drain electrode 102, and its concentration range is 1 × 10
14cm
-3to 1 × 10
20cm
-3.
The invention has the beneficial effects as follows, by the above-mentioned gallium nitride radical heterojunction field effect pipe with composite field plate structure in body, can find out, it is by introducing insulating medium layer, can blocking buffer layer leak channel, reduce OFF state drain current, then the possibility that device occurs to puncture in advance is reduced, and because the breakdown electric field of insulating medium layer is far above semi-conducting material, a part can be born withstand voltage, the introducing of this insulating medium layer, the Electric Field Distribution between grid and drain electrode can also be changed, make electric field more even, increase withstand voltage, and composite field plate structure in the body increased, significantly can modulate electric field distribution in channel, the effect of this Electric Field Modulated effect depends on structural parameters and the location parameter of field plate itself, than before surface field plate structure, more can depletion drift region electron concentration, electric field can be raised in consequent space charge region, increase withstand voltage, and this relation that can change between voltage endurance capability and conducting resistance, namely conducting resistance is reduced by increasing raceway groove N-type doping content, keep even improving voltage endurance capability simultaneously, also the figure of merit (FOM) of existing device is namely improved.
Accompanying drawing explanation
Fig. 1 is the structural representation of existing GaN HFET device;
Fig. 2 is the structural representation with the gallium nitride radical heterojunction field effect pipe of composite field plate structure in body of the present invention;
Fig. 3 is the Relationship Comparison figure of device drain current and drain bias under grid is in OFF state situation in device and Fig. 2 in Fig. 1;
Fig. 4 be in Fig. 1 in device and Fig. 2 device under grid is in OFF state situation along the comparison diagram of the Electric Field Distribution of raceway groove;
Wherein, 101 is source electrode, and 102 is drain electrode, and 103 is grid, and 104 is aluminum gallium nitride barrier layer, and 105 is gallium nitride channel layer, and 106 is nitride buffer layer, and 107 is substrate, and 208 is electrode, and 209 is insulating medium layer.
Embodiment
Below in conjunction with drawings and Examples, describe technical scheme of the present invention in detail.
The structural representation with the gallium nitride radical heterojunction field effect pipe of composite field plate structure in body of the present invention as shown in Figure 2, it comprises substrate 107, nitride buffer layer 106, gallium nitride channel layer 105, aluminum gallium nitride barrier layer 104, source electrode 101, drain electrode 102, composite field plate structure in grid 103 and body, wherein nitride buffer layer 106 is arranged on above substrate 107, gallium nitride channel layer 105 is arranged on above nitride buffer layer 106, aluminum gallium nitride barrier layer 104 is arranged on above gallium nitride channel layer 105, source electrode 101 and drain electrode 102 form ohmic contact with aluminum gallium nitride (AlGaN) barrier layer 104, grid 103 and aluminum gallium nitride (AlGaN) barrier layer 104 form Schottky contacts, in body, composite field plate structure is made up of electrode 208 and insulating medium layer 209, the horizontal level of electrode 208 is between grid 103 and drain electrode 102, the lower surface of electrode 208 contacts with device lower surface, insulating medium layer 209 covers electrode 208 and is positioned at substrate 107, in nitride buffer layer 106 and gallium nitride channel layer 105 other on the surface, in body composite field plate structure vertical direction on thickness be less than the distance of upper surface to substrate 107 lower surface of gallium nitride channel layer 105.
Embodiment
See Fig. 1, for the structural representation of existing GaN HFET device, comprise substrate 107, gallium nitride (GaN) resilient coating 106, gallium nitride (GaN) channel layer 105, the source electrode 101 that aluminum gallium nitride (AlGaN) barrier layer 104 and aluminum gallium nitride (AlGaN) barrier layer 104 are formed, drain electrode 102 and grid 103, wherein nitride buffer layer 106 is arranged on above substrate 107, gallium nitride channel layer 105 is arranged on above nitride buffer layer 106, aluminum gallium nitride barrier layer 104 is arranged on above gallium nitride channel layer 105, source electrode 101 and drain electrode 102 form ohmic contact with aluminum gallium nitride (AlGaN) barrier layer 104, grid 103 and aluminum gallium nitride (AlGaN) barrier layer 104 form Schottky contacts.
See Fig. 2, for the structural representation with the gallium nitride radical heterojunction field effect pipe of composite field plate structure in body of the present invention, it comprises substrate 107, nitride buffer layer 106, gallium nitride channel layer 105, aluminum gallium nitride barrier layer 104, source electrode 101, drain electrode 102, composite field plate structure in grid 103 and body, wherein nitride buffer layer 106 is arranged on above substrate 107, gallium nitride channel layer 105 is arranged on above nitride buffer layer 106, aluminum gallium nitride barrier layer 104 is arranged on above gallium nitride channel layer 105, source electrode 101 and drain electrode 102 form ohmic contact with aluminum gallium nitride (AlGaN) barrier layer 104, grid 103 and aluminum gallium nitride (AlGaN) barrier layer 104 form Schottky contacts, in body, composite field plate structure is made up of electrode 208 and insulating medium layer 209, the horizontal level of electrode 208 is between grid 103 and drain electrode 102, the lower surface of electrode 208 contacts with device lower surface, insulating medium layer 209 covers electrode 208 and is positioned at substrate 107, in nitride buffer layer 106 and gallium nitride channel layer 105 other on the surface, in body composite field plate structure vertical direction on thickness be less than the distance of upper surface to substrate 107 lower surface of gallium nitride channel layer 105.
Wherein, electrode 208 can be made up of metal or high doping semiconductor material, and insulating medium layer 209 can be made up of silicon dioxide and/or aluminium oxide and/or silicon nitride and/or hafnium oxide etc.In body, composite field plate structure width is in the horizontal direction less than the distance between grid 103 to drain electrode 102.The electricity connected mode of electrode 208 is for being biased separately or being connected with source electrode 101 or being connected with grid 103 or being connected with drain electrode 102.
Here, gallium nitride channel layer 105 can not artificially adulterate, and also can artificially N-type adulterate, if doping, then doping content scope is 1 × 10
14cm
-3to 1 × 10
20cm
-3.Nitride buffer layer 106 can be N-type doping content in the part of the close drain electrode 102 of insulating medium layer 209, and its concentration range is 1 × 10
14cm
-3to 1 × 10
20cm
-3.
This example with the GaN HFET with composite field plate in body (being made up of electrode 208 and insulating medium layer 209) shown in Fig. 2 under channel layer 205 adulterates and undopes two kinds of situations with the contrast of existing common GaN HEMT (Fig. 1); Device architecture parameter is see table 1.
Table 1 device simulation structural parameters
See Fig. 3, for device in device in Fig. 1 and Fig. 2 drain under grid is in OFF state situation 102 electric currents with drain electrode 102 bias voltages Relationship Comparison figure; Device electric breakdown strength is defined as drain electrode 102 electric current when reaching 1mA/mm, the bias voltages that drain electrode 102 applies.Result is two Dimension Numerical Value emulation gained.In Fig. 3, dash line drains under representing the cut-off state of common GaN HEMT device 102 electric currents; Chain-dotted line is that its raceway groove does not adulterate by 202 electric currents that drain under the cut-off state of the GaN HEMT of composite field plate in the belt body in this example; Solid line represents that wherein raceway groove has N-type doping content 1 × 10 by 202 electric currents that drain under the cut-off state of the GaN HEMT of composite field plate in the belt body in this example
17cm
-3.As seen from the figure, in body, composite field plate can reduce the drain leakage current under device cut-off state greatly.In addition, when there being composite field plate in body, N-type doping being carried out to raceway groove, can further improve device withstand voltage ability, reducing conducting resistance simultaneously.
In order to verify that in the body that is made up of insulating medium layer 209 and electrode 208, composite field plate structure is on the impact of device electric breakdown strength further, the distribution in raceway groove electric field strength transversely direction in following three kinds of situations by two Dimension Numerical Value simulation study, see Fig. 4, for device in device in Fig. 1 and Fig. 2 under grid is in OFF state situation along the comparison diagram of the Electric Field Distribution of raceway groove, in belt body in composite field plate raceway groove non-impurity-doped (Fig. 4 chain lines), belt body composite field plate and raceway groove N-type doping 1 × 10
17cm
-3(in Fig. 4 solid line) and ordinary construction (Fig. 4 dashed lines).Two conclusions as can be drawn from Figure 4.One is the distribution that in body, composite field plate structure obviously changes raceway groove electric field.Specifically, near the field plate introduced, there is a peak electric field in raceway groove, reduced the electric field at grid 103 edge, made electric field distribution in channel more even, thus improve the voltage endurance capability of raceway groove.Two is when there being channel doping, and in body, composite field plate effectively can exhaust the impurity of channel region, and leaving space charged region is with lifting electric field strength, increase withstand voltage, what is more important, while increase is withstand voltage, because doping, makes device on-resistance reduce.Specifically, to the situation only having composite field plate in body, conducting resistance is 0.54m Ω cm
2; Having composite field plate in body and raceway groove has N-type doping content 1 × 10
17cm
-3under situation, conducting resistance is 0.46m Ω cm
2.
The above is only present pre-ferred embodiments, not does any pro forma restriction to the present invention, every according in technical spirit of the present invention to any simple modification, equivalent variations that above embodiment is done, all fall within protection scope of the present invention.