# US 5,703,899 A · Gain-coupling distributed feedback semiconductor and method of producing the same > Agents: this data is available as JSON from the patentgrep API and MCP server — see https://patentgrep.com/llms.txt - Number: US 5,703,899 A - Document ID: US5703899A - Status: Granted - Kind: A - Application number: 08/659,114 - Filed: 1996-06-03 - Granted: 1997-12-30 - Earliest claimed: 1993-03-01 - Assignees: Canon Kabushiki Kaisha - Inventors: Natsuhiko Mizutani - Web page: https://patentgrep.com/patent/US5703899A ## CPC - H01S 5/1228: {DFB lasers with a complex coupled grating, e.g. gain or loss coupling} - H01S 5/3081: {using amphoteric doping} - H01S 5/3428: {layer orientation perpendicular to the substrate} - H01S: DEVICES USING THE PROCESS OF LIGHT AMPLIFICATION BY STIMULATED EMISSION OF RADIATION [LASER] TO AMPLIFY OR GENERATE LIGHT; DEVICES USING STIMULATED EMISSION OF ELECTROMAGNETIC RADIATION IN WAVE RANGES OTHER THAN OPTICAL ## Abstract There is a phenomenon that, when an epitaxial growth is performed on an uneven surface, such as a periodical surface or grating surface, having surfaces with different surface indices, p- and n-type layer portions can be simultaneously formed depending on growth surface orientations if an impurity such as Si or group IV elements is used. In a gain-coupling distributed feedback laser of the present invention, that phenomenon is utilized, and a current restraint layer, which includes alternately-arranged p- and n-type layer portions, is formed in the vicinity of an active layer. Thus, current is unevenly injected into the active layer, and a periodical gain structure can be established. As a result, a distributed feedback structure is achieved, which performs a gain-coupling operation. ## Claims ### Claim 1 A gain-coupling distributed feedback semiconductor laser comprising: a waveguide including an active layer; and a current restraint layer formed along said waveguide, said current restraint layer including p- and n-type semiconductor portions which are periodically and alternatively arranged along a light propagation direction; wherein said current restraint layer is grown on a periodic uneven surface, wherein pitch of carrier density of current injected by said current restraint layer is equal to a value of one half of a pitch of the periodic uneven surface. ### Claim 2 (depends on 1) A gain-coupling distributed feedback semiconductor laser according to claim 1, wherein said p- and n-type semiconductor portions are alternately arranged at a pitch which is equal to 1/2.times.(natural number).times.(a wavelength of light propagating along said waveguide). ### Claim 3 (depends on 1) A gain-coupling distributed feedback semiconductor laser according to claim 1, wherein said p- and n-type semiconductor portions are respectively amphi-conductuvity impurity-doped layers grown on layer portions having different surface orientations. ### Claim 4 (depends on 3) A gain-coupling distributed feedback semiconductor laser according to claim 3, wherein said amphi-conductivity impurity is Si. ### Claim 5 (depends on 1) A gain-coupling distributed feedback semiconductor laser according to claim 1, wherein said active layer comprises a multi-quantum well structure. ### Claim 6 (depends on 1) A gain-coupling distributed feedback semiconductor laser according to claim 1, wherein light confinement layers are respectively formed under and above said active layer. ### Claim 7 (depends on 6) A gain-coupling distributed feedback semiconductor laser according to claim 6, wherein a carrier block layer is formed on one of said light confinement layers. ### Claim 8 (depends on 7) A gain-coupling distributed feedback semiconductor laser according to claim 7, wherein a light guide layer is formed on said carrier block layer. ### Claim 9 (depends on 8) A gain-coupling distributed feedback semiconductor laser according to claim 8, wherein said current restraint layer is formed on said light guide layer. ### Claim 10 (depends on 7) A gain-coupling distributed feedback semiconductor laser according to claim 7, wherein said current restraint layer is formed on said carrier block layer. ### Claim 11 (depends on 1) A gain-coupling distributed feedback semiconductor laser according to claim 1, wherein said uneven surface has a trapezoidal sectional shape. ### Claim 12 (depends on 1) A gain-coupling distributed feedback semiconductor laser according to claim 1, wherein said uneven surface has an asymmetric sectional shape. ### Claim 13 A method of fabricating a gain-coupling distributed feedback semiconductor laser, said method comprising the steps of: forming a periodic uneven surface having a plurality of kinds of surfaces with different surface indices; and forming a current restraint layer on the uneven surface by simultaneously forming p- and n-type semiconductor portions on the uneven surface using a gas-phase crystal growth method. ### Claim 14 (depends on 13) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 13, wherein said gas-phase crystal growth method is one of molecular beam epitaxy, chemical beam epitaxy, metal organic molecular beam epitaxy, and gas source molecular beam epitaxy methods, and an amphi-conductivity impurity of group IV is used as an impurity. ### Claim 15 (depends on 13) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 13, wherein said gas-phase crystal growth method is the metal organic vapor phase epitaxy method, and an amphi-conductivity impurity of group IV is used as an impurity. ### Claim 16 (depends on 13) A gain-coupling distributed feedback semiconductor laser according to claim 13, wherein said p- and n-type semiconductor portions are alternately arranged at a pitch which is equal to 1/2.times.(natural number).times.(a wavelength of light propagating along said waveguide). ### Claim 17 (depends on 13) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 13, wherein the p- and n-type semiconductor portions are respectively amphi-conductivity impurity-doped layers grown on the uneven surface. ### Claim 18 (depends on 17) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 17, wherein said amphiconductivity impurity is Si. ### Claim 19 (depends on 13) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 13, wherein the uneven surface has a trapezoidal sectional shape. ### Claim 20 (depends on 13) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 13, wherein the uneven surface has an asymmetric sectional shape. ### Claim 21 (depends on 13) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 13, wherein the uneven surface is formed using wet etching with sulphuric acid series etchant. ### Claim 22 (depends on 13) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 13, wherein the uneven surface is formed using light wet etching with sulphuric acid series etchant that is performed after dry etching. ### Claim 23 A gain-coupling distributed feedback semiconductor laser comprising: a waveguide including an active layer; and a current restraint layer formed along said waveguide, said current restraint layer including p- and n-type semiconductor portions which are periodically and alternatively arranged along a light propagation direction; wherein said p- and n-type semiconductor portions are respectively amphi-conductivity impurity doped semiconductor layers grown on a periodic uneven surface. ### Claim 24 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein said p- and n-type semiconductor portions are alternately arranged at a pitch which is equal to 1/2.times.(natural number).times.(a wavelength of light propagating along said waveguide). ### Claim 25 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein said amphi-conductivity impurity is Si. ### Claim 26 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein said active layer comprises a multi-quantum well structure. ### Claim 27 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein light confinement layers are respectively formed under and above said active layer. ### Claim 28 (depends on 27) A gain-coupling distributed feedback semiconductor laser according to claim 27, wherein a carrier block layer is formed on one of said light confinement layers. ### Claim 29 (depends on 28) A gain-coupling distributed feedback semiconductor laser according to claim 28, wherein a light guide layer is formed on said carrier block layer. ### Claim 30 (depends on 29) A gain-coupling distributed feedback semiconductor laser according to claim 29, wherein said current restraint layer is formed on said light guide layer. ### Claim 31 (depends on 28) A gain-coupling distributed feedback semiconductor laser according to claim 28, wherein said current restraint layer is formed on said carrier block layer. ### Claim 32 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein said a periodic uneven surface has a pitch equal to a pitch of modulation of carrier density of current injected into said current restraint layer. ### Claim 33 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein said periodic uneven surface has a pitch equal to one half of a pitch of modulation of carrier density of current injected into said current restraint layer. ### Claim 34 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein said uneven surface has a triangular sectional shape. ### Claim 35 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein said uneven surface has a trapezoidal sectional shape. ### Claim 36 (depends on 23) A gain-coupling distributed feedback semiconductor laser according to claim 23, wherein said uneven surface has an asymmetric sectional shape. ### Claim 37 A method of fabricating a gain-coupling distributed feedback semiconductor laser, said method comprising the steps of: forming a periodic uneven surface having a plurality of kinds of surfaces with different surface indices; and forming a current restraint layer on the uneven surface by simultaneously forming p- and n-type semiconductor portions on the uneven surface using a gas-phase crystal growth method; wherein a pitch of carrier density of current injected by said current restraint layer is equal to one half of a pitch of the periodic uneven surface. ### Claim 38 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein said gas-phase crystal growth method is one of molecular beam epitaxy, chemical beam epitaxy, metal organic molecular beam epitaxy, and gas source molecular beam epitaxy methods, and an amphi-conductivity impurity of group IV is used as an impurity. ### Claim 39 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein said gas-phase crystal growth method is a metal organic vapor phase epitaxy method, and an amphi-conductivity impurity of group IV is used as an impurity. ### Claim 40 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein said p- and n-type semiconductor portions are alternately arranged at a pitch which is equal to 1/2.times.) (natural number).times.(a wavelength of light propagating along said waveguide). ### Claim 41 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein said amphiconductivity impurity is Si. ### Claim 42 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein the periodic uneven surface has a pitch equal to a pitch of modulation of carrier density of current injected into the current restraint layer. ### Claim 43 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein periodic uneven surface has a pitch equal to one half of a pitch of modulation of carrier density of current injected into the current restraint layer. ### Claim 44 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein the uneven surface has a triangular sectional shape. ### Claim 45 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein the uneven surface has a trapezoidal sectional shape. ### Claim 46 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein the uneven surface has an asymmetric sectional shape. ### Claim 47 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein the uneven surface is formed using wet etching with sulphuric acid series etchant. ### Claim 48 (depends on 37) A method of fabricating a gain-coupling distributed feedback semiconductor laser according to claim 37, wherein the uneven surface is formed using light wet etching with sulphuric acid series etchant that is performed after dry etching.