CN100448024C - Bipolar transistor with graded base layer - Google Patents

Abstract

A semiconductor material which has a high carbon dopant concentration includes gallium, indium, arsenic and nitrogen. The disclosed semiconductor materials have a low sheet resistivity because of the high carbon dopant concentrations obtained. The material can be the base layer of gallium arsenide-based heterojunction bipolar transistors and can be lattice-matched to gallium arsenide emitter and/or collector layers by controlling concentrations of indium and nitrogen in the base layer. The base layer can have a graded band gap that is formed by changing the flow rates during deposition of III and V additive elements employed to reduce band gap relative to different III-V elements that represent the bulk of the layer. The flow rates of the III and V additive elements maintain an essentially constant doping-mobility product value during deposition and can be regulated to obtain pre-selected base-emitter voltages at junctions within a resulting transistor.

Description

The bipolar transistor that graded base layer is arranged

Relevant patent application

This part application is the U.S. Patent application the 10/121st of application on April 10th, 2002, No. 444 continuation application, 10/121, No. 444 applications are the United States Patent (USP)s 09/995 as application on November 27th, 2000, No. 079 part continuation application, 09/995, No. 079 application requires the United States Patent (USP) provisional application the 60/253rd of application on November 27 calendar year 2001, No. 159 rights and interests are all integrated with this paper by quoting as proof with it at this.This part application also requires No. the 60/370th, 758, the United States Patent (USP) provisional application of on April 5th, 2002 application and the rights and interests of No. the 60/371st, 648, the United States Patent (USP) provisional application of applying on April 10th, 2002, by quoting as proof it is all integrated with this paper at this.

Prior art of the present invention

Bipolar junction transistor (BJT) and heterojunction bipolar transistor (HBT) integrated circuit (ICs) have developed into the important technology that is fit to multiple application, in particular for power amplifier, the microwave instrumentation of wireless phone be used for the high speed (＞10Gbit/s) circuit of optical fiber telecommunications system.Following needs expection is to need the device lower with production cost that operating voltage is lower, frequency performance is higher, power added efficiency is higher.Threshold voltage (the V of BJT or HBT _{Be, on}) be restricted to and realize a certain fixing Collector Current Density (J _c) requisite base-emitter voltage (V _Be).Threshold voltage can limiting device be subjected to the validity of low power applications of the power demand restriction of battery technology and other components and parts for output power.

Be different from the BJT that wherein emitter, base stage and collector electrode are made with a kind of semi-conducting material, HBT makes with two kinds of different semi-conducting materials, and wherein the emitter semiconductor material has than the big band gap (also being called " energy gap ") of semi-conducting material of making base stage.This causes the outstanding injection efficiency of charge carrier from the base stage to the collector electrode on BJT, stops charge carrier to postback emitter-base bandgap grading from the base stage injection because there is fixing barrier.Select the less base stage of band gap to reduce threshold voltage, because the increase that enters from base stage at charge carrier aspect the injection efficiency of collector electrode will increase Collector Current Density under given base-emitter voltage.

Yet HBT may suffer in the row infringement of the shortcoming of interruption suddenly of leading group of people that can cause at emitter-base stage interface of HBT at the heterojunction semiconductor material of conduction band spike.The effect of this conduction band spike is the blocking-up electronics enters collector electrode from base stage migration.Thereby electronics remains in base stage more for a long time, thereby causes compound level to increase and collector current gain (β _Dc) reduce.As previously discussed, because being restricted to, the threshold voltage of heterojunction bipolar transistor realizes the requisite base-emitter voltage of a certain fixing Collector Current Density, the threshold voltage of HBT so the gain of reduction collector current raises effectively.Therefore, be necessary further improving aspect the making of the semi-conducting material of HBT, in order that reduce threshold voltage and improve the device of low voltage operating whereby.

General introduction of the present invention

The HBT of the emitter of base stage that the invention provides the collector electrode that mixes by n-, forms at the material that forms on the collector electrode and the n-doping that on base stage, forms by the III-V family that comprises indium and nitrogen.The material of the III-V family of base layer has about 1.5 * 10 ¹⁹Cm ^-3To about 7.0 * 10 ¹⁹Cm ^-3Carbon dopant concentration.In preferred embodiments, base layer comprises element gallium, indium, arsenic and nitrogen.The existence of indium and nitrogen reduces the band gap of material with respect to the band gap of GaAs.In addition, dopant concentration is high in the material, surface resistivity (R _Sb) be low.These factors cause with respect to the lower threshold voltage of HBT that the similar GaAs base layer of dopant concentration is arranged.

In preferred embodiments, the compound-material system of III-V family can use chemical formula Ga _1-xIn _xAs _1-yN _yExpression.Well-known Ga _1-xIn _xThe energy gap of As descends in fact when a spot of nitrogen is merged in material.And, because nitrogen pushes away lattice constant by the direction opposite with indium, Ga _1-xIn _xAs _1-yN _yAlloy can be by growing the lattice that mates with GaAs to suitable indium/nitrogen than being added in the material.Therefore, cause the excessive strain energy of band gap increase and mispairing material dislocation to be eliminated.Therefore indium/nitrogen is more chosen than, so that reduce or eliminate strain.In a preferred embodiment of the invention, at the Ga of HBT _1-xIn _xAs _1-yN _yX=3y in the base layer.

In traditional HBT that GaAs is arranged, current gain usually since the hole to emitter inject higher, the space charge layer recombination current is higher and may lack in the base stage diffusion length and to successively decrease along with temperature increases progressively.In the HBT that the GaInAsN base layer is arranged, have found that along with temperature rising current gain significantly increases (about every rising increases by 0.3% for 1 ℃).This result is interpreted as along with temperature rising diffusion length increases.If be limited in to the state of small part localization and along with the increasing progressively of temperature at the electronics that can be with the bottom, they are subjected to thermal excitation and jump to other state of the easier diffusion of electronics from those states, and so such effect is expected.Therefore, make the temperature profile and the needs that reduce the temperature-compensating auxiliary circuit that base layer will be improved HBT of the present invention with GaInAsN.

There is the HBT of GaInAsN base layer to have the common emitter output characteristic of the improvement that surpasses traditional HBT that the GaAs base layer is arranged.For example, there is the HBT of GaInAsN base layer to compare bucking voltage and knee voltage is all lower with traditional HBT that the GaAs base layer is arranged.

In one embodiment, transistor is the bipolar transistor (DHBT) of double heterojunction, and the semi-conducting material of wherein forming base stage is different from the semi-conducting material of making emitter and collector.In the preferred embodiment of DHBT, Ga _1-xIn _xAs _1-yN _yBase layer can be used chemical formula Ga _1-xIn _xAs _1-yN _yExpression, collector electrode is GaAs, and emitter is selected from InGaP, AlInGaP and AlGaAs.

Another preferred embodiment of the present invention relates to HBT or DHBT, wherein the height of conduction band spike because of with base layer energy gap (E _Gb) reduction in conjunction with and descend.The conduction band spike is to be caused by the discontinuity at the conduction band of base/emitter heterojunction or base stage/collector electrode heterojunction.To reduce the conduction band spike by making base layer and emitter and/or collector layer lattice match reduce lattice strain.This normally concentration by nitrogen and indium in the control base layer realize.Preferably, base layer has chemical formula Ga _1-xIn _xAs _1-yN _y, wherein x approximates 3y greatly.

In one embodiment, base stage can be form to go up classification, so that it is less and at the bigger graded bandgap layer of emitter band gap to be created in the collector electrode band gap.Preferably, the base layer band gap arrives about 120meV in the base layer surface ratio of contact collector electrode at the low about 20meV in the base layer surface of contact emitter.More preferably, the band gap of base layer in base layer from collector electrode to the emitter linear change.

Add the band gap that nitrogen and indium will reduce material in the GaAs semi-conducting material.Therefore, semi-conducting material Ga _1-xIn _xAs _1-yN _yCompare with GaAs and to have lower band gap.The base layer Ga of classification on composition of the present invention _1-xIn _xAs _1-yN _yIn, the band gap of base layer reduces near collector electrode greater than close emitter.Yet, to compare with the band gap of GaAs, the average bandgap minimizing of crossing base layer is typically about 10meV to about 300meV.In one embodiment, compare with the band gap of GaAs, the average bandgap minimizing of crossing base layer is typically about 80meV to about 300meV.In another embodiment, with the band gap comparison of GaAs, the average bandgap minimizing of crossing base layer is typically about 10meV to about 200meV.The band gap of this minimizing will cause by the base layer Ga that forms classification _1-xIn _xAs _1-yN _yThe threshold voltage (V of HBT _{Be, on}) be lower than the HBT that the GaAs base layer is arranged, because V _{Be, on}Main decisive be carrier concentration intrinsic in the base stage.Intrinsic carrier concentration (n _i) be to calculate from following formula:

n _i＝N _cN _vexp(-E _g/kT)

In the equation above, N _cIt is the effective density of conduction band state; N _vIt is the effective density of valence band state; E _gIt is band gap; T is a temperature; And k is the Boltzmann constant.As what can see from formula, intrinsic carrier concentration is subjected to the control of the band gap of the material that uses in the base stage to a great extent in the base stage.

The band gap of base layer from the band gap big at the base-emitter interface to introducing quasi-electric field in the little bandgap graded in base stage-collector electrode interface, this electric field accelerated electron in npn type bipolar transistor crosses base layer.Electric field increases the velocity of electrons in the base stage, thereby reduces the base stage transit time, improves RF (radio frequency) performance and improves collector current gain (also being called the dc current gain).Dc (the β that gains _Dc) under the situation of the HBT of the base layer that a large amount of doping are arranged, be subjected to the restriction of the prose style free from parallelism reorganization in the neutral base stage (n=1).The dc current gain can be estimated with formula 1:

β _dc＝vτ/w _b (1)

In formula (1), v is a minority carrier average speed in base stage; τ is a minority carrier lifetime in base stage; And w _bIt is base thickness.The base layer of suitable classification causes with unassorted GaInAsN base layer and compares because velocity of electrons increases β in the HBT that the GaInAsN base layer is arranged _DcSignificantly increase.

For the band gap of classification on the thickness that is implemented in base layer, base layer is like this preparation, so that the concentration of its indium and/or nitrogen is higher than base layer second surface near emitter at the base layer first surface near collector electrode.The variation of indium and/or nitrogen content preferably changes linearly across base layer, thereby causes the band gap of linear classification.Preferably, the concentration of dopant (for example, carbon) keeps invariable everywhere in base layer.In one embodiment, Ga _1-xIn _xAs _1-yN _yBase layer, the base layer of DHBT for example is such classification so that x and 3y approximating greatly near the collector electrode 0.01 and by classification near emitter, being approximately zero.In another embodiment, Ga _1-xIn _xAs _1-yN _yBase layer is such classification, promptly the base layer surface of contact collector electrode x numerical value about 0.2 to about 0.02 scope internal classification at the base layer Surface Numerical x of contact emitter in about scope of 0.1 to 0, as long as numerical value x on the base layer surface of contact collector electrode greater than surperficial in the base layer of contact emitter.In this embodiment, can to keep invariable in base layer everywhere maybe can be linear classification to y.As y the time by linear classification, base layer is such classification, promptly from the base layer surface of contact collector electrode in about 0.2 y numerical value classification in about 0.02 the scope to the y numerical value in about scope of 0.1 to 0 on the base layer surface of contact emitter, as long as numerical value y on the base layer surface of contact collector electrode greater than the base layer surface of contact emitter.In preferred embodiments, x near about 0.006 the collector electrode by linear classification near emitter about 0.01.In more preferred, x near about 0.006 the collector electrode by near linear classification about 0.01 to emitter, and y is about 0.001 in base layer everywhere.

In another embodiment, the present invention is the method that forms the semiconductor layer of classification, and this semiconductor layer has from first surface and passes this layer to the second surface band gap of linear classification and the product of constant in essence doping-mobility in essence.This method comprises:

(a) product of the doping-mobility of comparison calibration layer, each alignment layer is to form under the distinct flow velocity of deposition from one of the organo-metallic compound of the atom of the III of periodic table or V family or carbon tetrahalide compound of deposit carbon, and the necessary organo-metallic compound of product and the carbon tetrahalide relative velocity that form constant in essence doping-mobility whereby are determined; With

(b) organo-metallic compound and carbon tetrahalide are flowed from the teeth outwards to form the product of constant in essence doping-mobility with described relative velocity, described flow velocity changes between depositional stage, forms the band gap of linear classification in essence so that pass the semiconductor layer of classification whereby.

Base layer also can be such dopant-classification, so that dopant concentration reduces to the Base-Emitter heterojunction gradually than thickness higher and that cross base stage near collector electrode.

Another method that makes the conduction band spike become minimum will comprise one or more heterojunction at transition zone.There is the transition zone of band gap layer, doping spike or its combination of low band gaps barrier layer, classification can be used to make the conduction band spike to become minimum.In addition, one or more lattice matching layers may reside between base stage and emitter or base stage and the collector electrode, so that reduce on material the lattice strain at heterojunction.

The present invention also provides the method for making HBT and DHBT.This method is included in the base layer that growth is made up of gallium, indium, arsenic and nitrogen on the n-Doped GaAs collector electrode.Base layer can utilize inside and/or outside carbon source to grow up, so that the base layer that provides carbon to mix.The emitter layer that n-mixes is grown on base layer subsequently.The carbon dopant that uses inside and outside carbon source to be provided for base layer can help to form the higher material of carbon dopant concentration ratio.Usually, about 1.5 * 10 ¹⁹Cm ^-3To about 7.0 * 10 ¹⁹Cm ^-3The level of mixing up be to use method of the present invention to realize.In preferred embodiments, about 3.0 * 10 ¹⁹Cm ^-3To about 7.0 * 10 ¹⁹Cm ^-3The level of mixing up can realize with method of the present invention.Higher dopant concentration will reduce the surface resistivity and the band gap of material in material.Therefore, dopant concentration is high more in the base layer of HBT and DHBT, and the threshold voltage of device is just low more.

The present invention also provides and uses chemical formula Ga _1-xIn _xAs _1-yN _yThe material of expression, wherein x and y are about 1.0 * 10 independently of one another ^-4To about 2.0 * 10 ^-1Preferably, x approximates 3y greatly.More preferably, x and 3y approximate 0.01 greatly.In one embodiment, material is with about 1.5 * 10 ¹⁹Cm ^-3To about 7.0 * 10 ¹⁹Cm ^-3Concentration mix with carbon.In specific embodiment, carbon dopant concentration is 3.0 about * 10 ¹⁹Cm ^-3To about 7.0 * 10 ¹⁹Cm ^-3

The minimizing of threshold voltage aspect can cause better managed about the normal voltage supply of being fixed of wired and wireless RF both circuits based on GaAs or the voltage budget of battery output restriction.Reduce threshold voltage also can change different base current compositions in based on the HBT of GaAs relative populations.Function DC current gain stability as junction temperature and applied stress before had been illustrated the relative populations that depends on each base current composition fatefully.Minimizing aspect the reverse hole injection that activates at low threshold voltage is favourable for the temperature stability and the long-term reliability of device.Therefore, the Ga of the no relative strain that dopant concentration is high _1-xIn _xAs _1-yN _yBase material can increase substantially the RF performance in based on the HBT of GaAs and DHBT.

Brief Description Of Drawings

Fig. 1 illustrates the InGaP/GaInAsNDHBT structure of the preferred embodiments of the invention, and wherein x approximates 3y greatly.

Fig. 2 is the Gummel curve, it with figure illustrate for InGaP/GaInAsN DHBT of the present invention and for the InGaP/GaAs HBT of prior art and GaAs/GaAs BJT along with the base stage of threshold voltage variation and the electric current of collector electrode.

Fig. 3 be with picture specification for InGaP/GaInAsN DHBT of the present invention and for the InGaP/GaAs HBT of prior art and GaAs/GaAs BJT with the threshold voltage of base surface resistance variations (at Jc=1.78A/cm ²).

Fig. 4 illustrate InGaP/GaInAsN DHBT of the present invention and and the InGaP/GaAs HBT (both base stage nominal thicknesses all are 1000 dusts) of prior art at the luminescence generated by light spectrogram of 77 ° of K actual measurements.The photoluminescence measurement result is etching away InGaAs and GaAs cover layer, is obtaining after the top of InGaP emitter stops selectively.The band gap of the n-type GaAs collector electrode of InGaP/GaAs HBT and InGaP/GaInAsN DHBT is 1.507eV.The band gap of the p-type GaAs base layer of InGaP/GaAs HBT is 1.455eV, and the band gap of the p-type GaInAsN base layer of InGaP/GaInAsN is 1.408eV.

Fig. 5 illustrates bicrystal X-ray diffraction (DCXRD) spectrum of the InGaP/GaAs HBT (nominal thickness of both base stages is 1500 dusts) of lnGaP/GaInAsN DHBT of the present invention and prior art.The peak of base layer is indicated.

Fig. 6 is a polaron C-V curve, and it illustrates the carrier concentration of crossing base layer thickness in the InGaP/GaAs HBT of InGaP/GaInAsN DHBT of the present invention and prior art.InGaP/GaInAsN DHBT and InGaP/GaAsHBT both have the base stage nominal thickness of 1000 dusts.Article two, the polaron curve all obtains after being etched down to the base layer top selectively.

Fig. 7 a illustrates the preferred structure of InGaP/GaInAsN DHBT, and this structure has at the transition zone between emitter and the base stage and transition zone between collector electrode and base stage and lattice matching layers.

Fig. 7 b and 7c illustrate the alternative structure by the InGaP/GaInAsN DHBT of the base layer of forming classification.

Fig. 8 be GaInAsN base layer that carbon mixes under the gas flow rate in fixing indium source during growth as the chart (" TMIF " is the trimethyl indium flow velocity) of the doping * mobility product of the function of carbon tetrabromide flow velocity.

Fig. 9 obtains the chart of the needed TMIF of product of constant doping * mobility with the carbon tetrabromide change in flow in the GaInAs base layer growth of forming classification that carbon mixes.

Figure 10 shows that threshold voltage is lower than the chart of the InGaP/GaInAsN HBT of InGaP/GaAs HBT.

Figure 11 is the Δ V of the carbon of growing under the fixing TMIF GaInAsN base layer of mixing _BeChart with the carbon tetrabromide change in flow.

Figure 12 is Δ V _BeChart with the TMIF variation.

Figure 13 is the structure of using in the experiment of embodiment 2 by the DHBT of the base layer of classification on forming.

Figure 14 is the structure of the DHBT that forms of the base layer by fixing used in the experiment of embodiment 2.

Figure 15 forms the Gummel curve that the DHBT of fixing DHBT and the classification on composition of GaInAsN base layer compares with the GaInAsN base layer.

Figure 16 forms DC current gain that the DHBT of fixing DHBT and the classification on composition of GaInAsN base layer the compares chart with the base surface resistance variations with the GaInAsN base layer.

Figure 17 forms the Gummel curve that fixing DHBT compares with the DHBT of GaInAsN base layer classification on forming and two kinds of GaInAsN base layers.

Figure 18 is that DHBT and two kinds of GaInAsN base layers of comparison GaInAsN base layer classification on forming are formed the chart of the DC current gain of fixing DHBT with the Collector Current Density variation.

Figure 19 is that comparison GaInAsN base layer is formed the chart of the current gain cutoff frequencies of fixing DHBT and the extrapolation of the DHBT of classification on forming of GaInAsN base layer with the Collector Current Density variation.

Figure 20 is that comparison GaInAsN base layer is formed the chart of the small signal current gain of fixing DHBT and GaInAsN base layer DHBT of classification on forming with the DHBT frequency change.

Figure 21 forms the peak value f of the DHBT of fixing GaInAsN base layer and the classification on forming of GaInAsN base layer to traditional HBT that the GaAs base layer is arranged _tWith BV _CeoThe chart that changes.

Figure 22 is the form of showing by the DHBT of the GaInAsN base layer of classification and tunnel collector electrode of forming.

Figure 23 is the band gap figure of the DHBT that describes of Figure 22.

Figure 24 is the Gummel curve of the DHBT that describes of Figure 22.

Figure 25 shows the common emitter characteristic of the DHBT that Figure 22 describes.

Detailed description of the present invention

Above-mentioned purpose, characteristic and advantage with other of the present invention is from following more detailed retouching The reference symbol that the usefulness of stating is identical represents the attached of a same part everywhere in different accompanying drawings The preferred embodiments of the invention that figure illustrates will become apparent. These pictures Needn't draw in proportion, but emphasize to illustrate principle of the present invention.

The III-V material be have comprise at least one from the element of the row III (A) of periodic table and At least one is from the semiconductor of the lattice of the element of the row V (A) of periodic table. At one In the embodiment, the lattice that the III-V material is made up of gallium, indium, arsenic and nitrogen. Preferably Be that the III-V material can be used chemical formula Ga_1-xIn _xAs _1-yN _yExpression, wherein x and y are about 1.0 * 10 independently of one another^-4To about 2.0 * 10^-1 More preferably, x is about Equal 3y. In the most preferred embodiment, x and 3y are about 0.01.

It is heterogeneous to refer to be positioned at base/emitter at term used herein " transition layer " Having active kind of the conduction band that makes hetero-junctions between knot or the base stage/colelctor electrode hetero-junctions drops to The rete of little function. Making the active a kind of method that drops to minimum of planting of conduction band is to use one to be Row transition layer makes the band gap of transition layer electric from the most close collection in base stage/colelctor electrode hetero-junctions The transition layer of the utmost point reduces gradually to the transition layer of close base stage. Similarly, at emitter stage In/base stage the hetero-junctions, the band gap of transition layer is from the transition layer of the most close emitter stage to the most close The transition layer of base stage reduces gradually. Minimized another kind method of the active kind of conduction band is to use The transition layer of bandgap graded. The band gap of transition layer can be by the dopant concentration with rete Classification and being graded. For example, the dopant concentration of transition layer can compare near the base stage layer Higher and can be near colelctor electrode or emitter stage reduce gradually. As an alternative, lattice Strain can be used to provide the transition layer of graded bandgap. For example, the transition layer can be Classification on the composition is so that the lattice strain is minimum and connecing at the film surface of contact base stage The surface of touching colelctor electrode or emitter stage increases the lattice strain. The minimumization conduction band is active plant in addition A kind of method is to use the active transition layer of planting of dopant concentration is arranged. One or more are above-mentioned The active kind method of minimumization conduction band that is used for can be used among the HBT of the present invention. Suitable The transition layer that closes HBT of the present invention comprises GaAs, InGaAs and InGaAsN.

Lattice matching layers is the rete that different lattice constants is arranged of growing at material. Brilliant Lattice coupling layer usually has the following thickness of about 500 dusts and defers in essence bottom film The lattice constant of layer. This cause the band gap of bottom film layer and lattice matched materials (if Strain does not take place in it) band gap between mid-gap between. The formation lattice matching layers Method be known to those skilled in the art and also can Ferry etc. people's Gallium Arsenide Technology (1985) 303-328 pages or leaves (Howard W.Sams ﹠ Co., Inc.Indianapolis, Indiana) in find, its whole contents citation merges to enter this paper. The example of the material of the lattice matching layers of the HBT of the present invention that is fit to is InGaP.

The base stage layer forms fixing HBT and DHBT

HBT of the present invention and DHBT can use suitable organic metal chemical vapor Deposition (MOCVD) epitaxial growth system prepares. Suitable MOCVD epitaxial growth The example of system is ALXTRON2400 and ALXTRON2600 platform. Using this Among the HBT and DHBT of the method preparation of invention, usually, the GaAs that does not mix is slow The punching layer can be grown after the desorb of oxide original place. For example, containing high concentration n-mixes up (for example, dopant concentration is about 1 * 10 to lower floor's collector layer of thing¹⁸cm ^-3To about 9 * 10¹⁸cm ^-3) can under about 700 ℃ temperature, grow. The collection that n-dopant concentration is low (for example, dopant concentration is about 5 * 10 to electrode layer¹⁵cm ^-3To about 5 * 10¹⁶cm ^-3) Can under about 700 ℃ temperature, grow at lower floor's colelctor electrode. Preferably, lower floor Colelctor electrode and colelctor electrode all are GaAs. Lower floor's collector layer has about 4000 dusts usually To the thickness of about 6000 dusts, and colelctor electrode has about 3000 dusts usually to about The thickness of 5000 dusts. In one embodiment, at lower floor's colelctor electrode and/or colelctor electrode In dopant be silicon. Non-essential be that InGaP lattice coupling tunnel layer can be typically Grow at colelctor electrode under the growth condition. Lattice-coupling layer has about 500 dusts usually Following thickness preferably approximately below 200 dusts, and has about 1x10¹⁶cm ^-3To about 1x10¹⁸cm ^-3Dopant concentration.

One or more transition layers can be optionally under typical growth condition If on the lattice matching layers or do not use lattice matching layers then grow at colelctor electrode. Cross Crossing layer can be from n-Doped GaAs, n-doping InGaAs or n-doping InGaAsN system Standby. The transition layer can optionally by forming or the dopant classification, maybe can comprise and mix up Thing is active plants. The transition layer has about 75 dusts usually to the thickness of about 25 dusts. If Do not use lattice matching layers or transition layer, the GaInAsN base stage layer that carbon mixes is at collection Grow on the electrode.

The base stage layer be under about temperature below 750 ℃, grow and also usually have big About 400 dusts are to the thickness of about 1500 dusts. In preferred embodiments, the base stage layer is Grow under about 600 ℃ temperature at about 500 ℃. Non-essential be that carbon is mixed If assorted GaInAsN base stage layer can be on the transition layer or do not use the transition layer Grow on the lattice matching layers. The base stage layer can be to use suitable gallium source (for example, front three Base gallium or triethyl group gallium), arsenic source (for example, arsine, tributyl arsine or trimethyl arsine), Indium source (for example, trimethyl indium) and nitrogen source (for example, ammonia or dimethylhydrazine) next life Long. Arsenic source to the low mole in gallium source than being preferred. Usually, arsenic source is to the gallium source Mole compares less than about 3.5. more preferably, and this ratio is about 2.0 to about 3.0. The level in nitrogen source and indium source be for obtain by about 0.01% to about 20% indium and Material that about 0.01% to about 20% nitrogen forms and adjusting. In preferred reality Execute in the scheme, indium content than the about Senior Three of nitrogen content doubly in the base stage layer. More preferably implementing In the scheme, indium content is about 1%, and nitrogen content is about 0.3%. In the present invention, Carbon dopant concentration is up to about 1.5 * 10¹⁹cm ^-3To about 7.0 * 10¹⁹cm ^-3 The GaInAsN layer is by using outside carbon source, organic metal source, especially gallium source Obtain. The example of suitable external carbon source is tetrabormated carbon. Carbon tetrachloride also is effective External carbon source.

Non-essential be that one or more transition layers can be between base stage and emitter stage The grown junction of the InGaAsN that the InGaAs that GaAs, the n-that n-mixes mixes or n-mix Really. Transition layer between base stage and emitter stage be mix comparatively slightly (for example, About 5.0 * 10¹⁵cm ^-3To about 5.0 * 10¹⁶cm ^-3) and optionally comprise dopant The active kind. Preferably, the transition layer is that about 25 dusts are thick to about 75 dusts.

Emitter layer be under about 700 ℃ temperature on base stage or optionally in mistake Cross the upper growth of layer, usually have about 400 dusts to the thickness of about 1500 dusts. Example As, emitter layer comprises InGaP, AlInGaP or AlGaAs. In preferred embodiment In, emitter layer comprises InGaP. Emitter layer can be with about 1.0 * 10¹⁷cm ^-3To about 9.0 * 10¹⁷cm ^-3Concentration n-mix. Comprise and contain high concentration (for example, greatly About 1.0 * 10¹⁸cm ^-3To about 9.0 * 10¹⁸cm ^-3) the GaAs emitter stage of n-dopant The contact layer is optionally grown at emitter stage under about 700 ℃ temperature. Usually, Emitter stage contact layer has about 1000 dusts to the thickness of about 2000 dusts.

Be the slope aspect the indium composition and also high concentration (for example, about 50 * 10 arranged¹⁸cm ^-3To about 5 * 10¹⁹cm ^-3) the InGaAs layer of n-alloy be in emission Grow on the utmost point layer. This rete has about 400 dusts to arrive the thick of about 1000 dusts usually Degree.

Embodiment 1

Explanation reduces the band gap of base layer and/or makes the effect of conduction band spike minimum, relatively three kinds of dissimilar bipolar transistor structures based on GaAs at the emitter/base heterojunction for example: GaAs emitter/GaAs base stage BJT, InGaP/GaAs HBT and InGaP/GaInAsN DHBT of the present invention.The general expression of the InGaP/GaInAsN DHBT structure of using in the experiment below is illustrated among Fig. 1.Has only a heterojunction at the emitter/base interface, because base stage and collector electrode are all formed by GaAs.The GaAs base layer of InGaP/GaAs HBT has the band gap greater than the base stage of InGaP/GaInAsNDHBT.GaAs/GaAs BJT does not have heterojunction, because emitter, collector electrode and base stage are all made with GaAs.Therefore, the structure of GaAs BJT is used as benchmark, does not have the collector current characteristic of InGaP/GaAs HBT to determine thing (if any) at base-emitter effect of the interface conduction band spike.In DHBT shown in Figure 1, InGaP is selected as emitter material, and base stage is Ga _1-xIn _xAs _1-yN _y, because InGaP has broad-band gap, and its conduction band and Ga _1-xIn _xAs _1-yN _yConduction band alignment.The InGaP/GaInAsN DHBT of Fig. 1 and the comparative result of InGaP/GaAs HBT are used to determine the influence of the lower base layer of band gap to Collector Current Density.

The GaAs device of Shi Yonging all has the base layer by the carbon doping of MOCVD growth in the following discussion, and wherein dopant concentration is from about 1.5 * 10 ¹⁹Cm ^-3Change to about 6.5 * 10 ¹⁹Cm ^-3And thickness changes to about 1500 dusts from about 500 dusts, thereby causes the base surface resistivity (R between 100 Ω/ and 400 Ω/ _Sb).Broad area device (L=75 μ m * 75 μ m) be make of simple wet etch method and by the common base configuration testing.Indium of relatively small amount (x～1%) and nitrogen (y～0.3%) add with being incremented, so that form two groups of independently InGaP/GaInAsN DHBT.For each group, it is optimised to grow, and mixes up level (＞2.5 * 10 to keep high uniform carbon ¹⁹Cm ^-3), good mobility (～85cm ²/ V-s) and high dc current gain (R _Sb～300 Ω/ time＞60).

Have GaAs/GaAs BJT, the InGaP/GaAs HBT of comparable base surface resistivity and the typical Gummel curve of InGaP/GaInAsN DHBT by oneself and be drawn into superimposed curve in Fig. 2.The collector current of InGaP/GaAs HBT and GaAs/GaAsBJT was indistinguishable with regard to the electric current of five above orders of magnitude (metric) before the differentia influence I-E characteristic of effective series resistance.On the other hand, the collector current of InGaP/GaInAsN DHBT is in the high twice of collector current of quite wide bias voltage scope internal ratio GaAs/GaAs BJT and InGaP/GaAs HBT, corresponding at 1.78A/cm ²Collector Current Density (J _c) threshold voltages minimizing 25.0mV.Observed increase aspect low bias voltage base current (n=2 composition) is consistent with the increase that drives in energy gap aspect the space charge reorganization in BJT.The neutral base stage of base current reassemble into branch in InGaP/GaInAsN DHBT with in InGaP/GaAs HBT, compare because increase and the minimizing of minority carrier lifetime or the increase (I of carrier velocity of collector current _Nbr=I _cw _b/ vr) be subjected to higher driving.Zhi Bei InGaP/GaInAsN DHBT device has realized for base surface resistivity being the device of 234 Ω/ so far, peak value dc current gain is 68, corresponding to threshold voltage minimizing 11.5mV with for base surface resistivity is the device of 303 Ω/, the current gain of peak value dc is 66, reduces 25.0mV corresponding to threshold voltage.This expression is for the ratio (β/R of these structure types the highest known gain with base surface resistivity _Sb～0.2-0.3).At Ga _1-xIn _xAs _1-yN _yThe energy gap minimizing is the reason that causes with the observed minimizing aspect threshold voltage of low temperature (77 ° of K) luminescence generated by light proof in the base stage.The DCXRD measurement result shows that the lattice mismatch of base layer is minimum (＜250 second of arcs (arcsec)).

In the limit of diffusion, bipolar transistor is with base-emitter voltage (V _Be) the desirable Collector Current Density that changes can be expressed as approx:

J _c＝(qD _nn ² _ib/p _bw _b)exp(qV _be/kT)(2)

Wherein

P _bAnd w _bBase implant and width;

D _nDiffusion coefficient;

n _IbIntrinsic carrier concentration in the base stage.

By n _IbBe expressed as base layer energy gap (E _Gb) function and rewrite base surface resistivity item (R _Sb) in the product of base implant and thickness, threshold voltage can be expressed as the logarithmic function of base surface resistance:

V _be＝-AIn[R _sb]+V _o (3)

A=(kT/q) (4) wherein

And V _o=E _Gb/ q-(kT/q) In[q ²μ N _cN _vD _n/ Jc] (5)

N wherein _cAnd N _vBe the effective density of state in conduction band and valence band, μ is a majority carrier mobility in the base layer.

Fig. 3 is at J _C=1.78A/cm ²The time many InGaP/GaAs HBT, GaAs/GaAsBJT and InGaP/GaInAsN DHBT threshold voltage with the curve of base surface change in resistance.Presenting the same logarithm dependence of expecting according to equation (2) qualitatively without any the InGaP/GaAs HBT of conduction band spike and the threshold voltage both of GaAs/GaAsBJT to base surface resistivity.Quantitatively, base-emitter voltage (Vbe) violent like that (A=0.0174 rather than the 0.0252mV) that do not have equation (3) to be showed with the variation of base surface resistivity.Yet the minimizing of this observed A is consistent with the accurate trajectory transmission by thin base stage GaAs bipolar device.

Relatively cause as drawing a conclusion with the characteristic of GaAs/GaAs BJT, promptly to present at collector current under the situation of ideal (n=1) state may be zero to the effective depth of the conduction band spike of InGaP/GaAsHBT.Therefore, InGaP/GaAs HBT can be designed like this, so that does not have the conduction band spike in essence.Similarly the result finds in the early stage work of AlGaAs/GaAs HBT.The threshold voltage that further reduces the base surface resistivity that these devices are suitable for fixing need use energy gap lower but still keep the successional base material of conduction band.Ga _1-xIn _xAs _1-yN _yCan be used to reduce E near the lattice match condition keeping _GbAs can be seen in Fig. 3, the threshold voltage of two groups of InGaP/GaInAsN DHBT is deferred to the logarithm dependence to base surface resistivity, thereby shows that the conduction band spike is approximately zero.In addition, threshold voltage offsets downward 11.5mV from InGaP/GaAs HBT and the observed numerical value of GaAs/GaAs BJT are offset downward in one group, and offsets downward 25.0mV (dotted line) in another group.

Above-mentioned description of test can be reduced to below the threshold voltage of GaAs BJT by using InGaP/GaInAsN DHBT structure based on the threshold voltage of the HBT of GaAs.Low threshold voltage is realized by two committed steps.At first, be in the base stage and the emitter semiconductor optimization of material base-emitter interface of energy level much at one by selecting conduction band, so that suppress the conduction band spike.This is successfully finished as base stage as emitter material and use GaAs by using InGaP or AlGaAs.Then, by reducing the band gap of base layer, further reduce threshold voltage.This is to realize by when still keeping the lattice match that spreads all over whole HBT structure indium and nitrogen being added in the base layer.Adopt suitable growth parameter(s), it is (at the Rsb=234 Ω/ time β=68) that is realizing under the situation of not sacrificing base implant or minority carrier lifetime greatly that Collector Current Density increases twice.These results show Ga _1-xIn _xAs _1-yN _yThe utilization of material provides a kind of method that is used for reducing based on the threshold voltage of the HBT of GaAs and DHBT.Because indium and nitrogen are incorporated the band gap that GaAs reduces material into,, be expected at based on the minimizing of threshold voltage in the HBT of GaAs and the DHBT also big more so if keep high p-type doping content, the percentage of incorporating the indium of base stage and nitrogen into is big more.

In the GaInAsN base stage, be assumed to be it is to cause the energy gap minimizing of the reason of observed threshold voltage minimizing to be confirmed by low temperature (77 ° of K) luminescence generated by light.Fig. 4 is relatively from InGaP/GaI _NThe luminescence generated by light spectrogram of AsN DHBT and traditional InGaP/GaAs HBT.Effect is in the energy lower than collector electrode (1.455eV is to 1.507eV) because the band gap that is associated with highly doped level narrows down from the base layer signal of InGaP/GaAs HBT.Narrow down effect and base layer energy gap reduces and is reduced because indium and nitrogen are incorporated band gap that base layer causes into from the base layer signal (appearing as 1.408eV) of InGaP/GaInAsN DHBT.This relatively in, therefore doped level is suitable, means with the energy gap of GaAs base stage and compares, and reduces the minimizing that may equal base layer energy gap in the GaInAsN base stage at the 47meV of base layer signal location.This skew in the luminescence generated by light signal is relevant well with the minimizing of the 45mV of the threshold voltage of actual measurement.When not having the conduction band spike, threshold voltage reduces the minimizing that may directly relate to the base layer energy gap.

Be illustrated in that DCRXD spectrum among Fig. 5 illustrates a carbon dopant and indium is added the semi-conductive effect of GaAs.Fig. 5 shows the DCRXD spectrogram from the InGaP/GaAs HBT of similar InGaP/GaInAsN DHBT of base thickness and standard.In InGaP/GaAs HBT, because 4 * 10 ¹⁹Cm ^-3The elongation strain that produces of high-carbon dopant concentration, base layer is counted as the dexter shoulder at GaAs bottom peak value, approximate position corresponding to+90 arcseconds (arcsec).Because add indium, in this specific I nGaP/GaInAsN DHBT structure, the base layer peak value is at-425 arcseconds (arcsec).In general, the peak that is associated with the GaInAsN base stage is the function of indium, nitrogen and concentration of carbon.Indium is added GaAs increases compression strain, and carbon and nitrogen compensate with elongation strain.

When indium (and nitrogen) is added the GaAs of carbon doping, keep high p-type doped level and need to optimize carefully growth.The rough estimate of active doped level can obtain from the base surface resistivity of actual measurement and the combination of base thickness numerical value.Base implant also can obtain polaron C-V distribution curve by the top that etches into base layer at first selectively then and be confirmed.Fig. 6 compares the such polaron C-V dopant profiles curve from GaAs base layer and GaInAsN base layer.In both cases, doped level all surpasses 3 * 10 ¹⁹Cm ^-3

Fig. 7 a shows the alternative structure that replaces GaInAsN base layer (10) fixing DHBT on forming, and it adopts transition zone (20 and 30) between emitter/base junction and collector electrode/base junction.In addition, transition zone and the inter-collector that lattice-coupling InGaP tunnel layer (40) is used in.

The DHBT of base layer classification on forming

Whole retes can both be grown to form the fixing similar mode of DHBT with base stage among the DHBT of classification on the base layer composition, and difference is that base layer makes a knot pass this rete as graded bandgap and indurates to transistorized another knot.For example, if neither use lattice matching layers also not use transition zone, GaInAsN base layer carbon-doping so and bandgap graded can be grown on collector electrode.Optionally, the GaInAsN base layer of the classification that carbon mixes can be grown on transition zone, if do not use transition zone, then grows on lattice matching layers.Base layer can about below 750 ℃ temperature growth and also the thickness of about 400 dusts to about 1500 dusts is arranged usually.In one embodiment, base layer is to arrive about 600 ℃ temperature growth at about 500 ℃.Base layer can be to use gallium source (for example, trimethyl gallium or triethyl-gallium), arsenic source (for example, arsine, three (tert-butyl group) arsine or trimethyl arsine), indium source (for example, for example trimethyl indium) and nitrogen source (for example ammonia, Dimethylhydrazine or tert-butylamine) to grow.The arsenic source is preferred with the low mol ratio in gallium source.Usually, arsenic source and the ratio mol ratio in gallium source are less than about 3.5.More preferably, this ratio is about 2.0 to about 3.0.The level in nitrogen and indium source can for the content that obtains III family element indium for about 0.01% to about 20% and the content of V group element nitrogen adjust to about 20% material for about 0.01%.In specific embodiment, the content of III family element (being indium) be from base-collector junction about 10% to 20% to changing at about 0.01% to 5% of base-emitter knot, the content of V group element (being nitrogen) is constant in essence about 0.3%.In another embodiment, the nitrogen content of base layer hangs down three times than indium content is about.Just form fixing GaInAsN base layer discussion as the front, we believe carbon dopant concentration height (about 1.5 * 10 ¹⁹Cm ^-3To about 7.0 * 10 ¹⁹Cm ^-3) the GaInAsN layer can be achieved by except the gallium source, using outside carbon source (for example carbon tetrahalide).For example, the carbon source of used outside can be a carbon tetrabromide.Carbon tetrachloride also is effective external carbon source.

Because the organo-metallic compound that uses as indium source gas is different from the organic gallium compound that uses as gallium source gas to the contribution of the content of carbon dopant in the GaInAsN base layer, so, carbon dopant source gas flow is adjusted at the base layer growing period usually, so that keep fixing carbon doping concentration in the GaInAsN base layer of classification on forming.In one embodiment, the variation of carbon source air-flow is to use the method for description to determine on the base layer of forming classification.

The carbon and three that is used for the InGaAs semiconductor layer of the GaInAsN of classification and/or classification Methyl indium source and course speed calibration procedure

At least prepare two groups of calibration HBT, wherein every group all comprises at least two members (DHBT can be used to replace HBT).Be to the base layer ideal thickness all the same for the calibration HBT of all formation, although this is dispensable, and each HBT is by fixing forming, for example, and composition that GaInAsN or GaInAs base layer are fixing and the fixing carbon dopant concentration that spreads all over this rete.Every group all is in the growth down of the III family that is different from another group or V family additive (for example, the nitrogen of the indium of III family or V family) source gas flow rate, so that each member in the particular group being made up of the member's who is different from other group gallium, indium, arsenic and nitrogen all.As an example, indium will be used as the additive that influences bandgap graded.Each member of particular group grows down at different external carbon source (for example, carbon tetrabromide or carbon tetrachloride) flow velocity, so that each member of particular group has different carbon to mix up level.The product of doping * mobility be determine at each member and also be the classification of relative carbon source flow velocity.The product of doping * mobility changes with the carbon source air velocity that is used for every group of each member with being directly proportional.With regard to five groups of HBT, the product of doping * mobility is plotted in Fig. 8 with the variation of carbon tetrabromide flow velocity.As an alternative, every group of calibration HBT may be by (for example keeping carbon-source gas, carbon tetrabromide) the constant formation of constant flow rate, and in every group each independently sample each be provided with may be with respect to other the flow velocity distinct III family of source gas or V family additive flow rate under form.

The needed carbon-source gas of product that obtains constant doping * mobility is to obtain by cross graph of a relation setting-out (straight line that for example, is parallel to the x-axle) by the product in constant doping * mobility in Fig. 8 to the relative velocity of indium source gas.The place representative that this line is cross-section and every group of straight line intersects obtains the flow of the needed external carbon source of product numerical value of this doping * mobility to for that setting when indium source gas flow is set at the flow velocity that is fit to that group.The external carbon source air velocity that is suitable for the product numerical value of a constant doping * mobility is plotted among Fig. 9 with the curve that indium source air velocity changes.The similar curve that is fit to the product of different doping * mobilities can be drawn in the same way.

The collector current of each HBT is as base-emitter voltage (V _Be) function draw, yet the electric current that is obtained with have the GaAs base layer aspect other but with the member of that group that is compared same (for example, the same dopant concentration, the same base stage, emitter and collector layer thickness, or the like) curve of HBT compares.Voltage differences between specific collector current lower curve is at base-emitter voltage [V _Be(Δ V _Be)] aspect is owing to added the change that base layer energy gap that indium and nitrogen causes reduces during base layer forms.Figure 10 shows that the collector current of HBT that the GaInAsN base layer is arranged and the HBT that the GaAs base layer is arranged is with V _BeThe curve that changes.The horizontal arrow that is drawn between two curves is Δ V _BeThe Δ V that is fit to each member in each group _BeBe determined and to carbon-source gas flow curve plotting.Each member's of five groups of HBT that curve among suitable formation Fig. 8 is used Δ V _BeCurve to the carbon tetrabromide flow is plotted among Figure 11.Please note: certain group membership's Δ V _BeCross that group can with the Δ V of fitting a straight line _BeScope.Then, these lines are used to determine that (insertion) is fit to the Δ V of some HBT _BeNumerical value, these HBT may be to use the same indium source gas flow rate of certain particular group but other member's who is different from this group carbon-source gas flow velocity growth is arranged.

The Δ V that is fit to the product of constant doping * mobility _BeFunction as indium source gas flow rate is linear change, and this is at the Δ V that draws at the product interpolation of constant doping * mobility _BeCan be in sight in the time of the curve that changes with indium source gas flow rate.Figure 12 shows that this is suitable for five groups curve used among Figure 11.

The graph of a relation of showing in Figure 12 is used to determine the Δ V in base-emitter and base stage/collector electrode junction acquisition expection _BeNeeded indium source gas flow.In case indium source gas flow is determined, Fig. 9 is used to determine the needed carbon-source gas flow of product that obtains the dopant * mobility of expection under that indium source gas flow.In order to maintain the product of the fixing dopant * mobility of expecting in the GaInAs that form to go up classification or the GaInAsN layer, determine indium source gas flow and carbon-source gas flow in base stage-collector electrode junction expection with following same program.When base layer from base stage-collector electrode junction surface to the base-emitter junction surface grow into into these source gas in the numerical value that these junction surfaces are determined, indium source gas flow and carbon-source gas flow are to change with respect to the horizontal linearity of gallium and arsenic, in order that obtain to have the base layer of linear classification of the band gap grade of expection.

Embodiment 2

Whole GaAs devices of Shi Yonging all have the base layer by the carbon-doping of MOCVD-growth in the following discussion, and wherein dopant concentration is from about 3.0 * 10 ¹⁹Cm ^-3Change to about 5.0 * 10 ¹⁹Cm ^-3, thickness changes to about 1500 dusts from about 500 dusts, thereby causes base surface resistivity (R _Sb) between 100 Ω/ and 650 Ω/.(L=75mm * 75mm) is to use that simple wet etch method is made and tests by the common base configuration broad area device.More a spot of indium (x～1% is to 6%) and nitrogen (y～0.3%) add with being incremented, to form two groups of independently InGaP/GaInAsN DHBT.In order to keep than higher uniform carbon dopant level (＞2.5 * 10 ¹⁹Cm ^-3), good mobility (～85cm ²/ V-s) and high dc current gain (at R _Sb～300 Ω/ time＞60), growth is optimized each group.The structure of the GaInAsN base layer of using in the experiment below DHBT of classification on forming is illustrated among Figure 13.The alternative structure that is used for base layer DHBT of classification on forming is illustrated in Fig. 7 b and 7c.The structure by the DHBT of the fixing GaInAsN base layer of forming that is used for comparing in the experiment below is illustrated among Figure 14.

Figure 15 shows Gummel curve fixing from base stage and DHBT comparable threshold voltage of having of classification and base surface resistance.The neutral base stage composition of base current is lower significantly in the base structure that can present than the classification of the fixing high peak value dc current gain more than 2 times of base structure.Figure 16 compares the dc current gain from the function of the conduct of the different similar DHBT structure fixing and classification of thickness.Be easy to see in the increase aspect the ratio of gain/base surface resistance.Although the ratio of the gain of DHBT/base surface resistance depends on growth conditions and the specific details of being utilized of general construction, the increase of having observed dc current gain in the DHBT of base layer classification already as one man surpasses the fixing DHBT50% to 100% of base layer.

Figure 17 and 18 will compare from the Gummel curve and the gain curve with from two kinds of fixing base structure of the base structure of classification.The base stage of first kind of fixing base structure is formed corresponding to the classification base stage and is formed in the base layer of base-emitter knot.The base stage of second kind of fixing base structure is formed corresponding to the classification base stage and is formed in the base layer of base emitter junction.The threshold voltage of classification base structure is two medians between the separation structure, but tilts to the base-emitter separation.The dc current gain of classification base structure is higher by 50% to 95% than the boundary dot structure, thereby shows that the major part increase of dc current gain derives from the increase of velocity of electrons.

FF test on the wafer is to use HP8510C parameter analyzer to finish on the device of the 4 μ m * 4 μ m emitter area of two finger-like.It is embedding that parasitic solder joint (pad parasitic) is to use open circuit and short-circuit structure (open and short structures) to remove, and current gain cutoff frequencies (f _t) be to extrapolate with the small signal current gain (H21) of-20 decibels/decimal system slope.Figure 19 is summarised in f on two kinds of structures _tWith Collector Current Density (J _c) dependence.Figure 20 illustrates in the variation of a specific bias point small signal gain with frequency.

Work as J _cIncrease and base stage transit time (t _b) beginning when sum provided constraints in the transit time, the f of classification base structure _tBecome significantly greater than forming fixing structure, no matter the bigger base thickness of classification base structure (fixing base layer is that 60nm is thick, and the base layer of classification is 80nm thick).60nm forms the peak value f of fixing GaInAsN base stage _tBe 53GHz, and the GaInAsN base stage of classification have the peak value f of 60GHz on the 80nm composition _tTherefore, current gain cutoff frequencies is increased 13%.

For the RF result of the GaInAsN base layer is fixing and DHBT classification preferably relatively and with traditional GaAs HBT compares mutually, from the f of Figure 19 _tNumerical value is drawn into adding to transistorized zero input current puncture voltage (BV _Ceo) curve that changes.The peak value of this curve and traditional GaAs HBT of quoting in the literature or near the f of peak value _tNumerical value compares.F at traditional GaAs HBT _tThe quite wide distribution in numerical value aspect expects because these data be according to the many groups of data editions of using different epitaxial structure, device size and test condition and also only be to be intended to the industrial standard of experiencing current.BV _CeoMajor part often has to suppose collector electrode thickness (), BV _CboWith the BV that shows among Figure 21 _CeoBetween the collector electrode thickness estimation of relation from quoting.In addition, suppose transit time (τ by the space charge layer of collector electrode _Sclc) by electronics saturated (drift) speed (v _s) and X _cRelevant simply, that show in Figure 21 is the f of expection _tTo BV _CeoThree kinds of dependence simple calculating.In baseline calculates, τ _bBe assumed that 1.115ps, as what expect according to the Monte-Carlo calculating of the GaAs base layer that is used for 1000 dusts, and the summation (τ of the transit time of remaining emitter and collector _e+ τ _c) be taken as 0.95ps.

Although the check of Figure 21 shows the f that forms fixing GaInAsN _tIncomplete face outside to the scope of traditional HBT expection based on GaAs, but the low side that it is obviously distributing.The base structure of classification is significantly improved.Second kind is calculated (τ _bReduce by 2/3 baseline) advise being reduced about 50% with respect to the transit time of forming fixing structure base stage.This shows with forming fixing base layer compares carrier velocity to increase by 1 times is to realize in the base layer of classification, increases by 33% combination with base thickness and will cause τ because goal pace increases by 1 times _bReduce by 1/2 * 4/3=2/3.The third calculating (τ _bReduce 1/3 and (τ _e+ τ _c) reduce by 1/2 baseline) approximately (make τ together with designs and the size improved _b, τ _eAnd τ _cMinimize) use the situation of base structure thin and/or classification together.

Embodiment 3

In order to improve efficiency of amplitude and therefore to reduce operating voltage and extending battery life, reduce bucking voltage (V _{CE, sat}) and knee voltage (V _k) need.A method that reduces bucking voltage is the asymmetry minimum that makes the right threshold voltage of base/emitter and base stage/collector diode.There is the DHBT of broad-band gap collector electrode to show the V that generation is low already _{CE, sat}Numerical value, but this causes higher Vk and lowers efficiency in practice, because the barrier potential of control base stage/collector electrode heterojunction is difficult.

There is the insertion of the thin layer (tunnel collector electrode) of high band gap to allow V _{CE, sat}And V _kReduce simultaneously, thus the efficient of raising device.Figure 22 shows the schematic diagram of the DHBT of GaInAsN base layer that classification is arranged and tunnel collector electrode.Base layer is such classification, so that has about 40meV bandgap energy difference between emitter junction and collector junction.The tunnel collector electrode that 100 dusts are thick is made between base stage and collector electrode, and it is by high band gap materials In _0.5Ga _0.5P forms.Figure 23 shows the band gap diagram of the DHBT of Figure 22.DHBT is to use that simple wet etching process is made as broad area device (L=75 μ m * 75 μ m) and tests by common base and common-emitter configuration.The common emitter characteristic that Figure 24 shows the Gummel curve and Figure 25 shows the DHBT that is suitable for Figure 22.As what can see from Figure 24 and 25, this device has the low bucking voltage of about 0.12V.

Equivalence

Although this invention showed particularly with reference to its preferred embodiment and described, those skilled in the art will appreciate that form and details aspect various changes can under the situation that does not break away from the scope of the present invention that claims include, finish.

Claims (58)

1. heterojunction bipolar transistor, comprising:

A) collector electrode of n-doping;

The base stage of the material that comprises III-V family that b) on collector electrode, forms, wherein the material of III-V family comprises indium and nitrogen, wherein base stage is mixed with carbon, and wherein base stage comprises product across the constant doping-mobility of base layer, base stage is classification on forming, so that be formed near the collector electrode band gap smaller and near emitter the bigger base layer of band gap, wherein base stage is with 1.5 * 10 with carbon ¹⁹Cm ^-3To 7.0 * 10 ¹⁹Cm ^-3Doped in concentrations profiled; And

C) emitter that the n-that forms on base stage mixes.

2. according to the transistor of claim 1, wherein base stage containing element gallium, indium, arsenic and nitrogen.

3. according to the transistor of claim 2, wherein collector electrode is GaAs, and emitter is InGaP, AlInGaP or AlGaAs, and transistor is a double hetero bipolar transistor.

4. according to the transistor of claim 2, wherein the base layer band gap is in low certain quantity between 20meV and 120meV of band gap on the base layer surface of the base layer surface ratio contact emitter of contact collector electrode.

5. according to the transistor of claim 4, wherein the band gap of base layer is from the base layer surface of contact collector electrode to the base layer surface linear classification of contact emitter.

6. according to the transistor of claim 5, wherein average band gap reduces in the scope between 20meV and 300meV less than the band gap of GaAs in the base layer of classification.

7. according to the transistor of claim 5, wherein average band gap minimizing is lacked 80meV to 300meV than the band gap of GaAs in the base layer of classification.

8. according to the transistor of claim 5, wherein average band gap minimizing is lacked 20meV to 200meV than the band gap of GaAs in the base layer of classification.

9. according to the transistor of claim 3, wherein base layer comprises that chemical formula is Ga _1-xIn _xAs _1-yN _yRete, wherein x and y are 1.0 * 10 independently of one another ^-4To 2.0 * 10 ^-1

10. according to the transistor of claim 9, wherein x equals 3y.

11. according to the transistor of claim 9, wherein x have near the numerical value between 0.2 and 0.02 collector electrode and also by classification near emitter between 0.1 to 0 numerical value, as long as x near the collector electrode greater than near emitter.

12. according to the transistor of claim 11, wherein x is other at collector electrode is 0.06, other at emitter is 0.01.

13. according to the transistor of claim 10, wherein base layer has the surface resistivity of 400 dusts to the thickness of 1500 dusts and 100 ohm-sq to 400 ohm-sq.

14. according to the transistor of claim 13, wherein the n-dopant is with between 3.5 * 10 in emitter ¹⁷Cm ^-3With 4.5 * 10 ¹⁷Cm ^-3Between concentration exist, and the n-dopant is with between 9 * 10 in collector electrode ¹⁵Cm ^-3To 2 * 10 ¹⁶Cm ^-3Between concentration exist.

15. according to the transistor of claim 13, wherein emitter and collector all is to use silicon doping.

16. according to the transistor of claim 14, wherein emitter has the thickness of 500 dusts to 750 dusts, and collector electrode has the thickness of 3500 dusts to 4500 dusts.

17. transistor according to claim 16, further comprise first transition zone that is deposited between base stage and the collector electrode, described first transition zone has the first surface with the first surface adjacency of base stage, and wherein first transition zone comprises the n-dopant material that is selected from GaAs, InGaAs and InGaAsN.

18. transistor according to claim 16, further include with the first surface of the first surface adjacency of emitter and with second transition zone of the second surface of the second surface adjacency of base stage, wherein second transition zone comprises the n-dopant material that is selected from GaAs, InGaAs and InGaAsN.

19. according to the transistor of claim 16, further include with the first surface of the first surface adjacency of collector electrode and with the lattice matching layers of the second surface of the second surface adjacency of first transition zone, wherein lattice matching layers is a wide bandgap material.

20. according to the transistor of claim 19, wherein lattice matching layers is selected from InGaP, AlInGaP and AlGaAs.

21. according to the transistor of claim 18, wherein first and second transition zones have the thickness of 40 dusts to 60 dusts.

22. according to the transistor of claim 18, wherein first and second transition zones have the thickness of 40 dusts to 60 dusts, and lattice matching layers has the thickness of 150 dusts to 250 dusts.

23. a formation has the method for the semiconductor layer of classification that the carbon of band gap grade and constant doping-mobility product mix by rete to second surface from first surface, this method comprises the steps:

A) form at least two group alignment layers, wherein every group of alignment layer comprises at least two members, and wherein:

I) each group alignment layer all is to form under the different flow velocity of the organo-metallic compound of the atom of III or V family in the deposition cycle table, and each member of each calibration group forms under the different flow velocity of the carbon tetrahalide compound of deposit carbon, perhaps

Ii) every group of alignment layer all is to form under the constant flow rate of the carbon tetrahalide compound of deposit carbon, and each member of each calibration group forms under the different in flow rate of the organo-metallic compound of the atom of III or V family in the deposition cycle table;

B) flow velocity of one of the organo-metallic compound of the atom of III or V family or carbon tetrahalide compound of described deposit carbon in the described deposition cycle table of contrast, the product of the doping-mobility of comparison calibration layer, the relative velocity that forms constant doping-needed organo-metallic compound of mobility product and carbon tetrahalide whereby is determined; With

C) organo-metallic compound and carbon tetrahalide compound are flowed from the teeth outwards with described relative speed, to form constant doping-mobility product, described flow velocity changes between depositional stage, forms to pass whereby to have 1.5 * 10 ¹⁹Cm ^-3To 7.0 * 10 ¹⁹Cm ^-3The band gap grade of linearity of semiconductor layer of classification of carbon doping concentration.

24., further be included in and make during the junction device step of deposition classification rete on second semiconductor layer according to the method for claim 23.

25. according to the method for claim 24, wherein second semiconductor layer is a collector layer.

26. according to the method for claim 24, wherein second semiconductor layer is an emitter layer.

27. according to the method for claim 23, wherein the semiconductor layer of classification comprises gallium, indium and arsenic, wherein determines the organo-metallic compound of the deposition rate of carbon tetrahalide to comprise organic indium compound in order to form constant doping-mobility product.

28. according to the method for claim 27, wherein carbon tetrahalide is CBr ₄Or CCl ₄

29. according to the method for claim 28, wherein organo-metallic compound further comprises nitrogen source gas.

30. according to the method for claim 29, wherein second semiconductor layer that deposits therein of the semiconductor layer of classification comprises GaAs.

31., further be included in the step of deposition the 3rd semiconductor layer on the base layer according to the method for claim 30.

32. according to the method for claim 31, wherein the 3rd semiconductor layer is InGaP.

33. method according to claim 30, wherein the doping of each alignment layer-mobility product is relevant with band gap, and band gap combines and will calibrate the relative velocity of requisite organic metal of the semiconductor layer that deposits described classification and carbon tetrahalide with the product of doping-mobility on first and second surfaces of classification rete whereby.

34. according to the method for claim 33, wherein said band gap is as using described alignment layer to calibrate with respect to GaAs the base-emitter voltage of the junction device of base layer.

35. according to the method for claim 34, wherein the semiconductor base stage layer of formed classification is the base layer in the heterojunction bipolar transistor.

36. according to the method for claim 35, wherein the flow velocity of organic metal and carbon tetrahalide makes the band gap of the base layer of final classification tie base-collector junction from the base-emitter of described heterojunction bipolar transistor to reduce gradually.

37. according to the method for claim 35, the source of gallium that wherein is used for the semiconductor base stage layer of classification is selected from trimethyl gallium and triethyl-gallium.

38. according to the method for claim 37, wherein the source of nitrogen is ammonia, dimethylhydrazine or tert-butylamine.

39. according to the method for claim 38, wherein the arsenic source is 2.0 to 3.5 with the ratio in gallium source.

40. according to the method for claim 39, wherein base stage is to grow being lower than under 750 ℃ the temperature.

41. according to the method for claim 40, wherein base stage is to grow under 500 ℃ to 600 ℃ temperature.

42. according to the method for claim 40, wherein base layer comprises that chemical formula is Ga _1-xIn _xAs _1-yN _yRete, wherein x and y are 1.0 * 10 independently of one another ^-4To 2.0 * 10 ^-1

43. according to the method for claim 42, wherein x equals 3y.

44. according to the method for claim 42, wherein collector electrode comprises GaAs, emitter comprises the material that is selected from InGaP, AlInGaP and AlGaAs, and transistor is a double hetero bipolar transistor.

45. method according to claim 42, further be included in the step of growth base layer first transition zone that growth n-mixes on collector layer before, wherein base layer is to grow on first transition zone that n-mixes, and first transition zone has the band gap of classification or the band gap littler than the band gap of collector electrode.

46. according to the method for claim 45, wherein first transition zone is selected from GaAs, InGaAs and InGaAsN.

47. method according to claim 46, further be included in before the emitter layer that growth n-mixes the step of growth second transition zone on base stage, wherein second transition zone have with the first surface of the surface adjacency of base stage first surface and with the second surface of the surface adjacency of emitter, and second transition zone has the doping content than little at least one order of magnitude of doping content of emitter.

48. according to the method for claim 47, wherein second transition zone is selected from GaAs, InGaAs and InGaAsN.

49. according to the method for claim 48, both have the doping spike wherein formed first transition zone, second transition zone or first and second transition zones.

50. method according to claim 48, further be included in before first transition zone that growth n-mixes the step of growth lattice matching layers on collector electrode, wherein lattice matching layers have with the first surface of the first surface adjacency of collector electrode and with the second surface of the second surface adjacency of first transition zone.

51. according to the method for claim 50, wherein lattice matching layers comprises InGaP.

52. semi-conducting material of making of the method for claim 23.

53. a material that comprises gallium, indium, arsenic and nitrogen, wherein the composition of material is to use chemical formula Ga _1-xIn _xAs _1-yN _yExpress, wherein x and y be independently of one another from the bigger numerical value of the first surface of material in the less numerical value classification of the second surface of material, and material have from first surface through rete to the constant carbon doping-mobility product of second surface, wherein material is with 1.5 * 10 ¹⁹Cm ^-3To 7.0 * 10 ¹⁹Cm ^-3Concentration and carbon mix.

54. according to the material of claim 53, wherein one of x and y are linear classifications at least.

55. according to the material of claim 54, wherein x is first surface from 0.01 to the 0.06 linear classification from the second surface of material to material.

56. a material that comprises gallium, indium, arsenic and nitrogen, wherein the composition of material is to use chemical formula Ga _1-xIn _xAs _1-yN _yExpress, wherein x be from the bigger numerical value of the first surface of material in the less numerical value classification of the second surface of material, and that y keeps in material everywhere is invariable, and material have from first surface through rete to the constant carbon doping-mobility product of second surface, wherein material is with 1.5 * 10 ¹⁹Cm ^-3To 7.0 * 10 ¹⁹Cm ^-3Concentration and carbon mix.

57. according to the material of claim 56, wherein x is linear classification.

58. according to the material of claim 57, wherein x from 0.01 to 0.06 linear classification, and the first surface of y from the second surface of material to material all is 0.001.

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