GB2354108A - Doping semiconductor layers - Google Patents
Doping semiconductor layers Download PDFInfo
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- GB2354108A GB2354108A GB9921249A GB9921249A GB2354108A GB 2354108 A GB2354108 A GB 2354108A GB 9921249 A GB9921249 A GB 9921249A GB 9921249 A GB9921249 A GB 9921249A GB 2354108 A GB2354108 A GB 2354108A
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- 239000004065 semiconductor Substances 0.000 title abstract description 12
- 239000012535 impurity Substances 0.000 abstract description 101
- 150000001768 cations Chemical class 0.000 abstract description 33
- 238000004519 manufacturing process Methods 0.000 abstract description 19
- 229910052796 boron Inorganic materials 0.000 abstract description 17
- 229910052782 aluminium Inorganic materials 0.000 abstract description 16
- 229910052733 gallium Inorganic materials 0.000 abstract description 7
- 229910052749 magnesium Inorganic materials 0.000 abstract description 5
- 229910052793 cadmium Inorganic materials 0.000 abstract description 3
- 229910052725 zinc Inorganic materials 0.000 abstract description 3
- 230000015572 biosynthetic process Effects 0.000 description 57
- 238000000034 method Methods 0.000 description 24
- 239000000463 material Substances 0.000 description 21
- 230000005281 excited state Effects 0.000 description 17
- ZOXJGFHDIHLPTG-UHFFFAOYSA-N Boron Chemical compound [B] ZOXJGFHDIHLPTG-UHFFFAOYSA-N 0.000 description 16
- 230000005428 wave function Effects 0.000 description 16
- XAGFODPZIPBFFR-UHFFFAOYSA-N aluminium Chemical compound [Al] XAGFODPZIPBFFR-UHFFFAOYSA-N 0.000 description 11
- 230000000737 periodic effect Effects 0.000 description 11
- 239000013078 crystal Substances 0.000 description 8
- 230000005283 ground state Effects 0.000 description 8
- 230000004913 activation Effects 0.000 description 7
- GYHNNYVSQQEPJS-UHFFFAOYSA-N Gallium Chemical compound [Ga] GYHNNYVSQQEPJS-UHFFFAOYSA-N 0.000 description 5
- 229910052738 indium Inorganic materials 0.000 description 2
- QIVUCLWGARAQIO-OLIXTKCUSA-N (3s)-n-[(3s,5s,6r)-6-methyl-2-oxo-1-(2,2,2-trifluoroethyl)-5-(2,3,6-trifluorophenyl)piperidin-3-yl]-2-oxospiro[1h-pyrrolo[2,3-b]pyridine-3,6'-5,7-dihydrocyclopenta[b]pyridine]-3'-carboxamide Chemical compound C1([C@H]2[C@H](N(C(=O)[C@@H](NC(=O)C=3C=C4C[C@]5(CC4=NC=3)C3=CC=CN=C3NC5=O)C2)CC(F)(F)F)C)=C(F)C=CC(F)=C1F QIVUCLWGARAQIO-OLIXTKCUSA-N 0.000 description 1
- 241000251737 Raja Species 0.000 description 1
- NWAIGJYBQQYSPW-UHFFFAOYSA-N azanylidyneindigane Chemical compound [In]#N NWAIGJYBQQYSPW-UHFFFAOYSA-N 0.000 description 1
- AYOOGWWGECJQPI-NSHDSACASA-N n-[(1s)-1-(5-fluoropyrimidin-2-yl)ethyl]-3-(3-propan-2-yloxy-1h-pyrazol-5-yl)imidazo[4,5-b]pyridin-5-amine Chemical compound N1C(OC(C)C)=CC(N2C3=NC(N[C@@H](C)C=4N=CC(F)=CN=4)=CC=C3N=C2)=N1 AYOOGWWGECJQPI-NSHDSACASA-N 0.000 description 1
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- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L29/00—Semiconductor devices specially adapted for rectifying, amplifying, oscillating or switching and having potential barriers; Capacitors or resistors having potential barriers, e.g. a PN-junction depletion layer or carrier concentration layer; Details of semiconductor bodies or of electrodes thereof ; Multistep manufacturing processes therefor
- H01L29/02—Semiconductor bodies ; Multistep manufacturing processes therefor
- H01L29/12—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed
- H01L29/20—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIIBV compounds
- H01L29/207—Semiconductor bodies ; Multistep manufacturing processes therefor characterised by the materials of which they are formed including, apart from doping materials or other impurities, only AIIIBV compounds further characterised by the doping material
-
- H—ELECTRICITY
- H01—ELECTRIC ELEMENTS
- H01L—SEMICONDUCTOR DEVICES NOT COVERED BY CLASS H10
- H01L33/00—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof
- H01L33/02—Semiconductor devices having potential barriers specially adapted for light emission; Processes or apparatus specially adapted for the manufacture or treatment thereof or of parts thereof; Details thereof characterised by the semiconductor bodies
- H01L33/26—Materials of the light emitting region
- H01L33/30—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table
- H01L33/32—Materials of the light emitting region containing only elements of Group III and Group V of the Periodic Table containing nitrogen
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- Microelectronics & Electronic Packaging (AREA)
- Power Engineering (AREA)
- Physics & Mathematics (AREA)
- Ceramic Engineering (AREA)
- Condensed Matter Physics & Semiconductors (AREA)
- General Physics & Mathematics (AREA)
- Computer Hardware Design (AREA)
- Crystals, And After-Treatments Of Crystals (AREA)
- Catalysts (AREA)
Abstract
A method of making a highly conductive p-type epitaxial layer of a Group III-nitride semiconductor comprises co-doping the layer with a Group II acceptor and an isoelectronic cation substitute impurity. The acceptor may be Mg, Zn or Cd and the cation substitute may be B, Al or Ga.
Description
ISOELECTRONIC CO-DOPING MIETECOD FOR OBTAINING OF IIIGHLY CONDUCTIVE F-
TYPE GALLIUM NrrREDE, ALUMDiUM NMUDE AND INDIUM NITRIDE SEMICONDUCTORS
BACKGROUND OF THE INVETMON
I.Field of the Invention
The present invention generally relates to a method of fabrication of highly conductive p-type III-nitride semiconductor epita3dal layers. More particularly, the invention deals with p-type doping method based on isoelectronic co-doping.
2. Description of the Prior Art
The elements from the IT row of the Periodic Table are used for fabrication p-type MNitride semiconductors since early times. However, the high bole binding energy -150 meV, and the low solubility for these elements in III-Nitride semiconductors do not allow to get highly conducfive p-type materials.
To overcome these difficulties several codoping methods have been suggested that use various complexes but without isoelectronic cations.
' present invention employs the complexes that include a shallow acceptor from U row of the Periodic Table and one, two, three or four isoelectronic cation substitute impurities with substitute cation mass lighter then host cation mass.
SUN04ARY OF THE INVENTION It is an object of the present invention to provide a p-type doping method that allows to obtain highly conductive 111-nitride semiconductors.
This invention states the use of the isoelectronic co-doping with the complexes that include a shallow acceptor from 11 row of the Periodic Table and one, two, three or four isoelectronic cation substitute impurities with substitute cation mass lighter then host cation mass.
The main advantages of the isoelectronic codoping method are 1. The reduction in the hole binding energy to the isoelectronic co- doping impurity complexes comparing to the hole binding energy to the acceptor impurity elements from the 11 row of the Periodic Table. The reduction in the hole binding energy to the isoelectronic co-doping impurity complexes results from local increase of semiconductor band gap in the vicinity of the isoelectronic cation substitute impurity with substitute cation mass lighter then host cation mass. This results in a strong local repulsion between the hole and the isoclectronic cation substitute impurity which makes the lowest acceptor states with admixture of s-type orbitals forbidden, because acceptor wave function should have go to zero at the location of the isoelectronic cation substitute impurity. When acceptor is surrounded by two, three, four or more isoelectronic cation substitute impurities the corresponding acceptor wave ftinction should have two, three, four or more zeros respectively. Therefore, for the acceptor surrounded by one or several isoelectrordc cation substitute impurities the lowest energy state or several lowest states are forbidden. The lowest acceptor excited states have energies about two or more times lower than for the main acceptor state [A. Baidereschi and N.O.Lipari, Phys. Rev. B8,2697 (1973), Y.T.Rebane Phys. Rev. B48, p.11772 (1993); J.-B. Xia et al Pbys. Rev. B59, p.10119 (1999)].
Thus, the shallow acceptor surrounded by one or several isoelectromc cation substitute impurities has the hole binding energy in two or more times lower than the acceptor without surrounding isoelecuonic cation substitute impurities.
2. The reduction in the hole binding energy leads to exponential increase in the hole concentration in the valence band and corresponding exponential increase in the hole conductivity of p-type MNitride semiconductor material by several orders of magnitude.
I The increase of the solubility of the acceptor impurity elements from the 1I row of the Periodic Table in the case when their covalent radii are higher dian the host cation covalent radius due to reduction of the formation energy. The reduction of the formation energy results from relaxation of the lattice strain around the isoelectronic co-doping impurity complexes. The strain energy AU associated with impurity complex can be estimated as AU= 3E(AV)' (I + V)V where AV is volume change associated with impurity atoms in the complex, V is the volume of the complex, E is Young modulus and v is the Poisson ratio. The reduction in the formation energy gives increase in solubility.
DETAILED DESCRIPTION OF THE PREFERRED EMBOMENTS
The preferred embodiments of the present invention is in the use of the isoelectronic co-doping with the complexes that include a shallow acceptor ftorn II row of the Periodic Table and one, two, three or four isoelectronic cation substitute impurities with substitute cation mass lighter then host cation mass.
The invention Yvill be more fully understood by reference to the following examples EXAMPLE I
AIN:Mg+B. The host crystal is AIN. The shallow acceptor impurity complex Mg+B. The direct energy gap for AIN is 6.2 eV, the direct energy gap for BN is much higher. Therefore, the effective potential for hole associated with boron substitute impurity is (rja)'AEv 6(r-r,), where rB = 0.89 A is tetrahedral covalent radius of boron impurity, AF, - I eV is valence band offset between BN and AIN and r. is boron impurity position. This potential is strongly repulsive for hole and, therefore, the Mg acceptor wave function should go to zero at r = r.. This makes the ground Mg acceptor state forbidden when B impurity is closer that acceptor wave function radius to the Mg impurity. Therefore, the binding energy of the hole to the Mg+B complex is equal to the energy of the first excited state of Mg acceptoT. The energy of the first excited state is about two times lower than the one for the ground state.
Thus, the binding energy of the hole to the Mg+B complex is in two times lower then the isolated Mg acceptor binding energy.
The lowering in the binding energy leads to lowering of the hole activation energy into valence band and higher free hole concentration in the valence band and results finally in a better p-type conductivity of the AIN doped with Mg+B.
Also, presence of boron impurities in AIN enhance the Mg acceptor solubility because of reduction in the Mg acceptor formation energy. The strain-related part AU of the formation can be estimated from the equation AU= 3E(A V)2 (I + V)V where A V is volume change associated with impurity atoms in the complex, V is the volume of the complex, E is Young modulus and v is the Poisson ratio for AIN.
For isolated Mg impurity the V and AV are given by V = (41r/3)(rA,)) and AV = (470)[ (rwg)' -(rA,)'], where rAj = 1,26A and rmg = 1.40 A are tetrahedral covalent radii of Al and Mg. The corresponding strain-related part AUm. of the formation estimated ftom, the above equation is AUmg - 3 eV.
For isolated B impurity the V and AV are given by V =: (4rJ3)(rA,)' and AV = (4rJ3)[ (rB)' - (rAj)' 1, where rp = 0. 89A.
The corresponding strain-related part AU of the formation esthnated from the above equation is A U,9 - 10 eV For the complex Mg+B the V and AV are given by V =: (W3 AI)3 and AV (47rJ3)[(rmY + (rp - 2(rAY). The corresponding strain-related part AUm g,B of the formation estimated from the above equation is A Qmg.B - I eV.
Thus, the reduction of the formation energy for Mg acceptor in the presence of B impurities is A UB + A Umg - A UM91B - 10 eV. This significant reduction in the formation energy gives increase in solubility by orders of magnitude.
EXAWLE2 AIN:Zn+B The host crystal is AIN. The shallow acceptor impurity complex is Zn+B. The direct energy gap for AIN is 6.2 eV, the direct energy gap for BN is much higher. Therefore, the effective potential for bole associated with boron substitute impurity is (rBAF-v 8(r-r.), where rB = 0.89 A is tetrahedral covalent radius of boron impurity, AE, - 1 eV is valence band offset between BN and AIN and r. is boron impurity position. This potential is strongly repulsive for hole and, therefore, the Zn acceptor wave fimction should go to zero at r = ro. This makes the ground Zn acceptor state forbidden when B unpunty is closer that acceptor wave function radius to the Zn impurity. Therefore, the binding energy of the hole to -the Zn+B complex is equal to the energy of the first excited state of Zn aweptor. The energy of the first excited state is about two times lower than the one for the ground state, Thus, the binding energy of the hole to the Zn+B complex is in two times lower then the isolated Zn acceptor binding energy.
The lowering in the binding energy leads to lowering of the hole activation energy into valence band and higher free hole concentration in the valence band and results finally in a better p-type conductivity of the AIN doped with Zn+B.
Also, presence of boron impurities in AIN enhance the Zn acceptor solubility because of reduction in the Zn acceptor formation energy. The strain-related part AU of the formation can be estimated from the equation AU= 3E(,&V)2 (I + V)v wbere AV is volume change associated with impurity atoms in the complex, V is the volume of the complex, E is Young modulus and v is the Poisson ratio for AIN.
For isolated Mg impurity the V and AV are given by V = (4x/3)(r,11)' and AV = (47d3)[ (rz,,)' - (rAj)'], where rAj = 1.26A and rz, = 1.31 A are tetrahedral covalent radii of At and Zn. The corresponding strain-related part AU7, of the formation estimated ftom the above equation is AU- 0.4 eV. For isolated B impurity the V and &V are given by V -- (4n/3 J(--Aj and AV = (4z3 A (rB)'- (rAi) 3, where rB = 0.89A.
The corresponding strain-related pan AUB of the formation estimated from the above equation isAUB - 10 eV For the complex Zn+B the V and A Y are given by V = (gir/3)(rAj and AV = (4ir/3)[(r7,)' + (rB)' - 2(rAl)']. The corresponding strain-related part A tJz,,.,,g of the formation estimated from the above equation is,&Uz,,,. s - I eV.
Thus, the reduction of the formation energy for Zn acceptor in the presence of B impurities is AUB + AUz,, - AUz,,,9 - 10 eV. This significant reduction in the formation energy gives increase in solubility by orders of magnitude, - q- EXAWLE 3 GaN: Mg+B. The host crystal is G-aNThe shallow acceptor impurity complex Mg+B. The direct energy gap for CTaN is 3-5 eV, the direct energy gap for BN is much higher. Therefore, the effective poiential for hole associated with boron substitute impurity is (rB) 3 AEv 6(r-r.), where rB = 0. 89 A is tetrahedral covalent radius of boron impurity, AE, - 2 eV is valence band offset between BN and GaN and r. is boron impurity position, This potential is strongly repulsive for hole and, therefore, the Mg acceptor wave function should go to zero at r = r.. This makes the ground Mg acceptor state forbidden when B impurity is closer that acceptor wave function radius to the Mg impurity. Therefore, the binding energy of the bole to the Mg+B complex is equal to the energy of the first excited state of Mg acceptor. The energy of the first excited state is about two times lower than the one for the ground state. Thus, the binding energy of the hole to the Mg+B complex is in two times lower then the isolated Mg acceptor binding energy.
The lowering in the binding energy leads to lowering of the hole aefivation energy into valence band and higher free hole concentration in the valence band and results finally in a better p-type conductivity of the GaN doped with Mg+B.
Also, presence of boron impurities in CmN enhance the Mg acceptor solubility because of reduction in the Mg acceptor formation energy. The strain-related part AU of the formation can be estimated from the equation AU= 3E(AV)2 (I + V)V where AV is volwne change associated with impurity atoms in the complex, V is the volume of the complex, F. is Young modulus and v is the Poisson ratio for GaN. For isolated M& itripurit y the V and AV are given by V = (470)(rc,) and A V = (4V3 (rM S)3 -(rGW)'], where rr, = 1.26A and rmg = 1.40 A are tetrahedral covalent radii of Al and Mg. The corresponding strain-related part A Um , of the formation is AQmg - 3 eV. For isolated B impurity the V and AV are given by V= (4;t/3)(rG,)3 andAy = (4n13)( (rB)3 _ (._(;,)3), where ra = 0.89A. The corresponding strain-related part Aus of the formation is A UB - 10 eV For the complex Mg+B the V and AV are given by V = (8rJ3)(rG. )3 and AV = (rC (420 Wrm, + (rB)' - 2 ')3]. The co nonding strain-related part &U the formation is A UAISIB - I eV.,Ig+,g of Thus, the reduction of the formation energy for Mg acceptor in the presence of B impurities is A(18 + AUtg - AUmg.,,8 eV. This significant reduction in the formation energy gives increase in solubility by orders of magnitude.
EXAMPLE4
GaN' Mg+Al. The host crystal is GaN. The shallow acceptor impurity complex mg+Al. The direct energy gap for GaN is 3.5 eV, the direct energy gap for AIN is 6.2 eV. Therefore, the effective potential for hole associated with aluminum substitute impurity is (17JAEv kr-r.), where TAI = 1.26 A is tetrahedral covalent radius of aluminum impurity, AF-,, - I eV is valence band offset between GaN and AN and r. is aluminum impurity position. This potential is strongly repulsive for hole and, therefore, the Mg acceptor wave function should go to zero at r r. This makes the ground Mg acceptor state forbidden when Al impurity is closer than aceeptor wave function radius to the Mg impurity. Therefore, the binding energy of the hole to the M9+AI complex is equal to the energy of the first excited state of Mg acceptor. The energy of the first excited state is about two times lower than the one for the ground state.
Thus, the binding energy of the hole to the Mg+Al complex is in two times lower then the isolated Mg acceptor binding energy.
The lowering in the binding energy leads to lowering of the hole activation energy into valence band and higher free hole concentration in the valence band and results finally in a better p-type conductivity of the GaN doped with Mg+Al.
Also, presence of aluminum impurities in GaN enhance the Mg acceptor solubility because of reduction in the Mg acceptor formation energy. The strain-related part A U of the formation can be estimated from the equation AU= 3E(AV)2 (I + V)V where,&Visvoluine change associated with impurity atoms in the complex, V is the volume of the complex, E is Young modulus and v is the Poisson ratio for GaN.
For isolated Mg impuril the V and AV are given by V = (4rJ3)(rG.) and AV (4xJ3)[ (rmj: -(rG.)], where rG. = 1,26A and rw, = 1.40 A are tetrahedral covalerd radii of Al and Mg. The corresponding strain-related part AUAf. of the formation is AUmg - 3 eV.
For isolated B impurity the V and AV are given by V = (420)(rc,,,)3 and A V = (4a/3)[ (rB)' - (rGa)'], where rB = 0.89 The corresponding strain-related part AUB of the formation is negligible according the above equation.
For the complex Mg+Al the V and AV are given by V = (Sx/3)(rA,)3 and AV = (4n/3)[(rAjg + (rv - 2(rG.)']. The corresponding strain-related part AUAt+ At of the formation is A (4Wg+B - 1.5 eV.
Thus, the reduction of the formation energy for Mg acceptor in the presence of A) impurities is AUB + AuRg - Auft,B - I ev. This small reduction in the formation energy is comparable with the accw-acy of the estimalion based on the above equation and can give some increase in solubility, - IID - EXAWLE 5 GaN: Zn+B. The host crystal is GaN. The shallow acceptor impurity complex Mg+B. The direct energy gap for GaN is 3.5 eV, the direct energy gap for BN is much higher. Therefore, the effective potential for hole associated with boron substitute impurity is (rB)3 AEv 5(r-r.), where ra = 0.89 A is tetrahedral covalent radius of boron impurity, AF, - 2 eV is valence band offset between BN and GaN and r. is boron impurity position. This potential is strongly repulsive for hole and, therefore, the Zn acceptor wave function should go to zero at r = r.. This makes the ground Zn acceptor state forbidden when B impurity is closer that acceptor wave function radius to the Zn impurity. Therefore, the binding energy of the hole to the Zn-4-B complex is equal to the energy of the first excited state of Zn acceptor. The energy of the first excited state is about two times lower than the one for the ground state. Thus, the binding energy of the hole to the Zn+B complex is in two times lower then the isolated Mg acceptor binding energy.
The lowering in the binding energy leads to lowering of the hole activation energy into valence band and higher free hole concentration in the valence band and results finally in a better p-type conductivity of the GaN doped with Zn+B.
Also, presence of boron impurities in GaN enhance the Zn acceptor solubility because of reduction in the Zn acceptor formation energy. The strain-related part AU of the formation can be estimated from the equation AU= 3F,(AV)2 (I + V)v whereA V is volume change associated with impurity atoms in the complex, V is the volume of the complex, E is Young modulus and v is the Poisson mtio for GaN.
For isolated Zn impurity the V and AV are given by V= (4r/3)(rG.)3 and AV ) [ (r7 (4a13)I 4rG.)3], Where rC;" = 1.26A and rz,, = 1.31 A are tet-ahral covalent radii of Ga and Zn. The corresponding strain-related part A Uz,, of the formation is AUz, - - 0.4 eV For isolated impurity the V and AV are given by V = (4aJ3 Xrc,,,)3 and A V = (4nJ3)[ (rp - (rc.], where rB = 0-89AThe corresponding strain-related part AUB of the formation is A UB - 10 eV For the complex Zn+B the V and AV are given by V = (8zJ3)(rA,)3 and AV = (rC (4rJ3)((rz,? + (rB)' - 2 J]. 'ne corresponding strain-related pal AUZtB Of the formation estimated from the above equation is AUz.,+,6 - 1 eV.
Thus, the reduction of the formation energy for Zn acceptor in the presence of B impurities is AQP + AUz, - AUz,,,.B - 10 eV. This significant reduction in the formation energy gives increase in solubility by orders of magnitude.
EXAMPLE6
GaN: Zn+Al. The host crystal is GaN. The shallow acceptor impurity complex 7-n+Al. The direct energy gap for GaN is 3.5 eV, the direct energy gap for AIN is 6.2 eV. Therefore, the effective potential for hole associated with aluminum substitute impurity is (rJAEv 8(r-r.), where r. 'M = 1.26 L is tetrahedral covalent radius of aluminurn impurity, AE,, - I eV is valence band offset between GaN and AIN and r. is aluminum impurity position. This potential is strongly repulsive for hole and, therefore, the Zn acceptor wave function should go to zero at r = r.. This makes the ground Zn acceptor state forbidden when Al impurity is closer than acceptor wave function radius to the Zn impurity. Therefore, the binding energy of the hole to the Zn+AI complex is equal to the energy of the first excited state of Zn acceptor. The energy of the first excited state is about two times lower than the one for the ground state. Thus the binding energy of the hole to the Mg+Al complex is in two times lower then the isolated Mg acceptor binding energy.
The lowering in the binding energy leads to lowering of the hole activation energy into -IZ- valence band and higher free hole concent-afion in the valence band and results finally in a better p-type conductivity of the GaN doped with Mg- 4-Al.
Also, presence of aluminum impurities in GaN enhance the Mg acceptor solubility because of reduction in the Mg acceptor formation energy. The strain-related part AU of the formation can be estimated from the equation AU = (I + V)V where AVis volume change associated with impurity atoms in the complex, V is the volume of the complex, E is Young modulus and v is the Poisson ratio for GaN.
For isolated Mg impunty the V and AV are given by f/ = (4rJ3)(rG,,)-and AV (4n/3)[ (%) 3 -(rG,,) 3 1, where rG. = 1.26A and rft = 1.40 A are teuuhedral covalent radii of Al and Mg. The corresponding strain-reWed part A U1,6, of the formation is AUmg - 3 eV.
For isolated B impurity the V and AV are given by V = (470 and AV = (4rJ3)[ (ro -), where rB = 0.89 A.
The corresponding strain-related part AUB of the formation is negligible according the above equation.
For the complex Mg+Al the V and AV are given by V= (SrJ3)(rA,)3 and AV (4n/3)[(rm g)' + (rAj)' - 2(,rG.)']. The corresponding strain-related part AUm,,,41 of the formation is A T7,Wg-B - 1.5 eV.
Thus, the reduction of the formation energy for Mg acceptor in the presence of A] impurities is A U9 + A Ugg - A Ums,,D - I eV. This small reduction in the formation energy is comparable with the accuracy of the estimation based on the above equation and can give some increase in solubility EXAMPLE 7
InN. Cd+Al. The host crystal is InN. The shallow acceptor impurity complex Gd+Al. The direct energy gap for InN is 2.0 eV, the -is- direct energy gap for AIN is 6.2 eV. Therefore, the effective potential for hole associated with aluminum substitute impurity is (rAjA]Ev S(r-r.), where ru = 1.26 A is tetrahedral covalent radius of aluminum impurity, AE, - 1.5 eV is valence band offset between InN and AIN and r. is aluminum impurity position. This potential is strongly repulsive for hole and, therefore, the Cd acceptor wave function should go to zero at r = r, This makes the ground Cd acceptor state forbidden when Al impurity is closer fim acceptor wave function radius to the Cd impurity. Therefore, the binding energy of the hole to the Cd+AJ complex is equal to the energy of the first excited state of Cd acceptor. The energy of the first excited state is about two times lower thwi the one for the ground state. Thus, the binding energy of the hole to the Cd+AI complex is in two times lower then the isolated Cd acceptor binding energy.
The lowering in the binding energy leads to lowering of the hole activation energy into valence band and higher ftee hole concentration in the valence band and results finally in a better p-type conductivity of the InN doped with Cd+AI.
Also, presence of aluminum impurities in InN enhance the Cd acceptor solubility because of reduction in the Cd aoceptor formation energy. The strain-related part A U of the formation can be estimated from the equation AU= 3E(AV)2 (I + V)V where AV is volume change associated with impurity atoms in the complex, V is the volume of the complex, E is Young modulus and v is the Poisson ratio for InN.
For isolated Cd impwi7 the V and AV are given by V - (470 Xrr,) and AV (4x/3)[ (rcd)' where rcf = 1.48A and rz. = 1.44 A are tetrahedral covalent radii of Cd and In. The corresponding strain-related part A Um. of the formation is AU,ie - 0.03 eV.
- i4_ For isolated A] impuril the V and AV are given by V = (4x/3 rjj) and A Y (4n/3)[ (rj - (rr.) 1, where rAj 1.26 A, rl, = 1.44 A.
The corresponding strain-related part AI41 of the formation is A UAj = 2 eV For the complex Cd+AI the V and AV are given by V= (8z/3 and AV = (4W3)[(rcd + (rAl)-' - 2(rl,,)31. The corresponding strain-related put AUcjAj of the formation is AUcdAl - 0.06 eV.
Thus, the reduction of the formation energy for Cd acceptor in the presence of A] impurities is A Ucj +A UAI - A UCd.Aj - 2 eV.
This significant reduction in the formation energy gives increase in solubility by orders of magnitude.
EXAWLE 8 InN: Cd+Ga. The host crystal is InN. The shallow acceptor impurity complex Gd+Ga. The direct energy gap for InN is 2.0 eV, the direct energy gap for GaN is 3.5 eV, Therefore, the effective potential for hole associated with gallium substitute impurity is (rc,.)3 AEv S(r-r.), where rG. = 1.26 A is tetrahedral covalent radius of gallium impurity, AF, - 0. 5 eV is valence band offset between InN and GaN and r. is gallium impurity position. This potential is strongly repulsive for hole and, therefore, the Cd acceptor wave function should go to zero at r = r.. This makes the ground Cd acceptor state forbidden when Ga impurity is closer than acceptor wave function radius to the Cd impurity. Therefore, the binding energy of the hole to the Cd+Ga complex is equal to the energy of the first excited state of Cd acceptor. The energy of the first excited state is about two times lower than the one for the ground state. Thus, the binding energy of the hole to the Cd+Ga complex is in two times lower then the isolated Cd accegor binding energy.
The lowering in the binding energy leads to lowering of the hole activation energy into valence band and higher free hole concentration in the valence band and results finally in a better p-type conductivity of the InN doped with Cd+CTa.
Also, presence of gallium impurities in InN enhance the Cd acceptor solubility because of reduction in the Cd acceptor formation energy. The strain-related part AU of the formation can be estimated from the equation AU= (I + V)V where AV is volume change associated with impurity atoms in the complex, V is the volume of the complm E is Young modulus and v is the Poisson ratio for InN.
For isolated Cd impuri,7 the V and AV are given by V = (4x/3 Xrl,) and AV = (4xG A (rat)' Wiffe rci = 1.49A and ri,, = 1.44 A are tetrahedral covalent radii of Cd and In. The corresponding strain-related part AUwg of the fonnation is AUA,rg - 0.03 eV.
For isolated Ga impuri the V and AV are given by V = 470 jrG,) and AV = OX/3)( (rav) - (ri.)], where rG,,, = 1.26 A, ri. = 1.44 A, The corresponding strain-related part AUG. of the fonnation is AUG, = 2 eV For the complex Cd+Ga the V and A Pr are given by V = (Sx/3 Xrj,,)3 and AV = (470)[(rcd + (rc.)' - 2(r.%)3J. The corresponding strain-related part AUcd,.G, of the formation is A Ucd+G. - 0. 06 eV.
Thus, the reduction of the formation energy for Cd acceptor in the presence of Ga impurities is A Ucr +A Ua,, - A (IcdC, - 2 W. This significant reduction in the formation energy gives increase in solubility by orders of magnitude.
LAIMS ft-- 1. The use of the isoelectronic co-doping method with the complexes that include a shallow acceptor from 11 row of the Periodic Table aud an isoelectronic cation substitute impurities with substitute cation mass lighter then host cation mass for fabrication highly conductive p-type 111-Nitride semiconductor materials.
2. The use of the isoelectronic co-doping method with the complexes that include a shallow acceptor fforn 11 row of the Periodic Table and two, three, four or more isoelectronic cation substitute impurities with substitute cation masses lighter then host cation mass for fabrication highly conductive p-type M-Nitride semiconductor materials.
3. The use of the isoelectronic co-doping method with the Mg+B complex for fabrication highly conductive p-type AIN materials.
4. The use of the isoelectronic co-doping method with the Zn+B complex for fabrication highly conductive p-type AIN materials.
5. The use of the isoelemonic co-doping method with the Mg+B complex for fabrication highly conductive p-t)V GaN materials.
6. The use of the isoelectronic co-doping method with the MS+Al complex for fabrication highly conductive "pe GaN materials.
7. The use of the isoelectronic co-doping method with the Zn+B complex for fabrication highly conductive p-type GaN materials.
8. The use of the isoelectronic co-doping method with the Zn+AI complex for fabrication highly conductive "pe GaN materials.
9. The use of the isoelectronic co-doping method with the Cd+Al complex for fabrication highly conductive p-type InN materials.
10. The use of ft isoelectronic cO-dOPiII9 method with the Cd+Ga complex for fabrication highly conductive p-type InN materials.
Amendments to the claims have been riled as follows I The use of an isoelectronic co-doping method with a complex that includes a shallow acceptor from Group 11 of the Periodic Table and an isoelectronic cation substitute impurity from Group III of the Periodic Table with a substitute cation mass lighter than the host cation mass, the host cation being fTom Group III of the Periodic Table, for the fabrication of a highly conductive p-type 111-Nitride semiconductor material.
2. The use of an isoelectronic co-doping method with an Mg+B complex for the fabricatl',-n of a highly conductive p-type AIN material.
3. The use of an isoelectronic co-doping method with a Zn+B complex for the fabrication of a highly conductive p-type AIN material.
4. The use of an isoelectronic co-doping method with an Mg+B complex for the fabrication of a highly conductive p-type GaN material. 5. The use of an isoelectronic co-doping method with an Mg+A1 complex for
the fab-Ication. of a highly conductive p-type GaN material.
6. The use of an isoelectronic co-doping method with a Zn+B complex for the fabrication of a highly conductive p-type GaN material.
7. The use of an isoelectronic co-doping method with a Zn+AI complex for the fabrication of a highly conductive p-type GaN material.
8. The use of an isoelectronic co-doping method with a Cd+A1 complex for the fabrication of a highly conductive p-type InN material.
9 The use of an isoelectronic co-doping method with a Cd+Ga complex for the fabri'cation of a highly conductive p-type InN material.
19 10. The use of an Isoelectronic co-doping method substantially in accordance with any of the Examples herein described.
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| GB9921249A GB2354108B (en) | 1999-09-08 | 1999-09-08 | An isoelectronic co-doping method |
| TW89115184A TW477011B (en) | 1999-09-08 | 2000-07-28 | Isoelectronic co-doping method |
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| GB9921249A GB2354108B (en) | 1999-09-08 | 1999-09-08 | An isoelectronic co-doping method |
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| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7122734B2 (en) * | 2002-10-23 | 2006-10-17 | The Boeing Company | Isoelectronic surfactant suppression of threading dislocations in metamorphic epitaxial layers |
Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0541373A2 (en) * | 1991-11-08 | 1993-05-12 | Nichia Chemical Industries, Ltd. | Method of manufacturing p-type compound semiconductor |
| US5652434A (en) * | 1993-04-28 | 1997-07-29 | Nichia Chemical Industries, Ltd. | Gallium nitride-based III-V group compound semiconductor |
| US5657335A (en) * | 1993-11-01 | 1997-08-12 | The Regents, University Of California | P-type gallium nitride |
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1999
- 1999-09-08 GB GB9921249A patent/GB2354108B/en not_active Expired - Fee Related
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Patent Citations (3)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| EP0541373A2 (en) * | 1991-11-08 | 1993-05-12 | Nichia Chemical Industries, Ltd. | Method of manufacturing p-type compound semiconductor |
| US5652434A (en) * | 1993-04-28 | 1997-07-29 | Nichia Chemical Industries, Ltd. | Gallium nitride-based III-V group compound semiconductor |
| US5657335A (en) * | 1993-11-01 | 1997-08-12 | The Regents, University Of California | P-type gallium nitride |
Cited By (2)
| Publication number | Priority date | Publication date | Assignee | Title |
|---|---|---|---|---|
| US7122734B2 (en) * | 2002-10-23 | 2006-10-17 | The Boeing Company | Isoelectronic surfactant suppression of threading dislocations in metamorphic epitaxial layers |
| US7626116B2 (en) | 2002-10-23 | 2009-12-01 | The Boeing Company | Isoelectronic surfactant suppression of threading dislocations in metamorphic epitaxial layers |
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| Publication number | Publication date |
|---|---|
| GB9921249D0 (en) | 1999-11-10 |
| TW477011B (en) | 2002-02-21 |
| GB2354108B (en) | 2001-08-08 |
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