1. Ama-semiconductor esizukulwane sesithathu
Ubuchwepheshe be-semiconductor besizukulwane sokuqala bathuthukiswa ngokusekelwe ezintweni ze-semiconductor ezifana ne-Si ne-Ge. Buyisisekelo sezinto ezibonakalayo sokuthuthukiswa kwama-transistors kanye nobuchwepheshe besekethe ehlanganisiwe. Izinto ze-semiconductor zesizukulwane sokuqala zabeka isisekelo semboni ye-elekthronikhi ngekhulu lama-20 futhi ziyizinto eziyisisekelo zobuchwepheshe besekethe ehlanganisiwe.
Izinto ze-semiconductor zesizukulwane sesibili zifaka phakathi i-gallium arsenide, i-indium phosphide, i-gallium phosphide, i-indium arsenide, i-aluminium arsenide kanye nama-compounds azo e-ternary. Izinto ze-semiconductor zesizukulwane sesibili ziyisisekelo semboni yolwazi lwe-optoelectronic. Ngalesi sisekelo, izimboni ezihlobene ezifana nokukhanyisa, ukubonisa, i-laser, kanye ne-photovoltaics ziye zathuthukiswa. Zisetshenziswa kabanzi kwezobuchwepheshe bolwazi besimanje kanye nezimboni zokubonisa ze-optoelectronic.
Izinto ezimele izinto ze-semiconductor zesizukulwane sesithathu zifaka i-gallium nitride kanye ne-silicon carbide. Ngenxa yegebe lazo elibanzi lebhendi, ijubane eliphezulu lokukhukhuleka kwe-electron saturation, ukuqhuba okuphezulu kokushisa, kanye namandla ensimu okuqhekeka okuphezulu, ziyizinto ezifanele zokulungiselela amadivayisi kagesi anamandla aphezulu, amaza aphezulu, kanye nokulahlekelwa okuphansi. Phakathi kwazo, amadivayisi kagesi e-silicon carbide anezinzuzo zobuningi bamandla aphezulu, ukusetshenziswa kwamandla aphansi, kanye nosayizi omncane, futhi anamathemba okusetshenziswa abanzi ezimotweni zamandla amasha, ama-photovoltaics, ezokuthutha ngesitimela, i-big data, kanye neminye imikhakha. Amadivayisi e-Gallium nitride RF anezinzuzo zobuningi bamandla aphezulu, amandla aphezulu, i-bandwidth ebanzi, ukusetshenziswa kwamandla aphansi kanye nosayizi omncane, futhi anamathemba okusetshenziswa abanzi ekuxhumaneni kwe-5G, i-Internet of Things, i-radar yezempi kanye neminye imikhakha. Ngaphezu kwalokho, amadivayisi kagesi asekelwe ku-gallium nitride asetshenziswe kabanzi ensimini yamandla aphansi. Ngaphezu kwalokho, eminyakeni yamuva nje, izinto ezintsha ze-gallium oxide kulindeleke ukuthi zakhe ukuhambisana kobuchwepheshe nobuchwepheshe obukhona be-SiC kanye ne-GaN, futhi zinamathemba okusetshenziswa angase abe khona emasimini anamandla aphansi kanye namandla aphezulu.
Uma kuqhathaniswa nezinto ze-semiconductor zesizukulwane sesibili, izinto ze-semiconductor zesizukulwane sesithathu zinobubanzi be-bandgap ebanzi (ububanzi be-bandgap ye-Si, into ejwayelekile yezinto ze-semiconductor zesizukulwane sokuqala, cishe yi-1.1eV, ububanzi be-bandgap ye-GaAs, into ejwayelekile yezinto ze-semiconductor zesizukulwane sesibili, cishe yi-1.42eV, kanti ububanzi be-bandgap ye-GaN, into ejwayelekile yezinto ze-semiconductor zesizukulwane sesithathu, bungaphezu kwe-2.3eV), ukumelana nemisebe okunamandla, ukumelana okunamandla kokuqhekeka kwensimu kagesi, kanye nokumelana nokushisa okuphezulu. Izinto ze-semiconductor zesizukulwane sesithathu ezinobubanzi be-bandgap ebanzi zifaneleka kakhulu ekukhiqizweni kwamadivayisi kagesi amelana nemisebe, ama-frequency aphezulu, amandla aphezulu kanye nokuhlanganiswa okuphezulu. Ukusetshenziswa kwazo kumadivayisi e-microwave radio frequency, ama-LED, ama-laser, amadivayisi kagesi nakwamanye amasimu kudonsele ukunaka okukhulu, futhi zibonise amathuba amaningi entuthuko kwezokuxhumana eziphathwayo, ama-smart grid, ezokuthutha ngesitimela, izimoto zamandla amasha, ama-electronics abathengi, kanye namadivayisi okukhanya kwe-ultraviolet nokuluhlaza okwesibhakabhaka [1].
Umthombo wesithombe: I-CASA, i-Zheshang Securities Research Institute
Isibalo 1 Isikali sesikhathi sedivayisi yamandla ye-GaN kanye nesibikezelo
Isakhiwo nezinto ze-II GaN kanye nezici
I-GaN iyi-semiconductor ye-bandgap eqondile. Ububanzi be-bandgap yesakhiwo se-wurtzite ekushiseni kwegumbi bungaba ngu-3.26eV. Izinto ze-GaN zinezakhiwo ezintathu eziyinhloko zekristalu, okuyisakhiwo se-wurtzite, isakhiwo se-sphalerite kanye nesakhiwo sikasawoti wedwala. Phakathi kwazo, isakhiwo se-wurtzite yisakhiwo sekristalu esizinzile kakhulu. Isithombe 2 siwumdwebo wesakhiwo se-wurtzite esinama-hexagonal se-GaN. Isakhiwo se-wurtzite sezinto ze-GaN singesakhiwo esinama-hexagonal esinama-athomu angu-12, kufaka phakathi ama-athomu angu-6 e-N kanye nama-athomu angu-6 e-Ga. I-athomu ngayinye ye-Ga (N) yakha isibopho nama-athomu angu-4 e-N (Ga) aseduze futhi ibekwe ngokulandelana kwe-ABABAB… ngendlela [0001] [2].
Umfanekiso 2 Isakhiwo seWurtzite umdwebo weseli lekristalu le-GaN
III Izisekelo ezivame ukusetshenziswa ze-GaN epitaxy
Kubonakala sengathi i-epitaxy efanayo kuma-substrate e-GaN iyona engcono kakhulu ye-epitaxy ye-GaN. Kodwa-ke, ngenxa yamandla amakhulu e-bond ye-GaN, lapho izinga lokushisa lifika endaweni yokuncibilika engu-2500℃, ingcindezi yayo yokubola ehambisanayo icishe ibe ngu-4.5GPa. Lapho ingcindezi yokubola iphansi kunale ngcindezi, i-GaN ayincibiliki kodwa ibola ngqo. Lokhu kwenza ubuchwepheshe bokulungiselela i-substrate obuvuthiwe njengendlela ye-Czochralski bungafaneleki ekulungiseleleni ama-substrate e-GaN single crystal, okwenza ama-substrate e-GaN abe nzima ukuwakhiqiza ngobuningi futhi abize kakhulu. Ngakho-ke, ama-substrate avame ukusetshenziswa ekukhuleni kwe-epitaxial ye-GaN ikakhulukazi yi-Si, i-SiC, i-sapphire, njll. [3].
Ishadi 3 i-GaN kanye namapharamitha ezinto ezisetshenziswa kakhulu ze-substrate
I-GaN epitaxy ku-sapphire
I-Sapphire inezakhiwo zamakhemikhali ezizinzile, ishibhile, futhi ikhula kahle embonini yokukhiqiza enkulu. Ngakho-ke, isibe ngesinye sezinto zokuqala nezisetshenziswa kakhulu ze-substrate kubunjiniyela bamadivayisi we-semiconductor. Njengenye yezingxenye ezisetshenziswa kakhulu ze-GaN epitaxy, izinkinga ezinkulu ezidinga ukuxazululwa zezingxenye ze-sapphire yilezi:
✔ Ngenxa yokungafani okukhulu kwe-lattice phakathi kwe-sapphire (Al2O3) ne-GaN (cishe u-15%), ubuningi besici esibonakalayo phakathi kwesendlalelo se-epitaxial kanye ne-substrate buphezulu kakhulu. Ukuze kuncishiswe imiphumela yaso emibi, i-substrate kumele iphathwe ngendlela eyinkimbinkimbi ngaphambi kokuba inqubo ye-epitaxy iqale. Ngaphambi kokutshala i-epitaxy ye-GaN kuma-substrate e-sapphire, ubuso be-substrate kumele buqale buhlanzwe ngokucophelela ukuze kususwe ukungcola, umonakalo osele wokupholisha, njll., futhi kukhiqizwe izakhiwo zezinyathelo nezinyathelo. Ngemuva kwalokho, ubuso be-substrate buhlungwa nge-nitride ukuze kushintshwe izakhiwo zokumanzisa zesendlalelo se-epitaxial. Ekugcineni, isendlalelo esincane se-AlN buffer (ngokuvamile esingu-10-100nm ubukhulu) sidinga ukufakwa ebusweni be-substrate futhi sifakwe emazingeni okushisa aphansi ukuze kulungiselelwe ukukhula kokugcina kwe-epitaxial. Noma kunjalo, ubuningi bokuhlukaniswa kwamafilimu e-GaN epitaxial akhuliswe ezindaweni ezingaphansi kwe-sapphire busephezulu kunobamafilimu e-homoepitaxial (cishe u-1010cm-2, uma kuqhathaniswa nobuningi bokuhlukaniswa okungu-zero kumafilimu e-silicon homoepitaxial noma amafilimu e-gallium arsenide homoepitaxial, noma phakathi kuka-102 no-104cm-2). Ubuningi obuphezulu bokuhlukaniswa kwezicubu kunciphisa ukuhamba kwezicubu, ngaleyo ndlela kufinyeze isikhathi sokuphila kwezicubu ezincane futhi kunciphise ukuhanjiswa kokushisa, konke okuzonciphisa ukusebenza kwedivayisi [4];
✔ I-coefficient yokwanda kokushisa kwe-sapphire inkulu kuneye-GaN, ngakho-ke ukucindezeleka kokucindezela kwe-biaxial kuzokhiqizwa kungqimba lwe-epitaxial ngesikhathi senqubo yokupholisa kusukela ekushiseni kokufakwa kuya ekushiseni kwegumbi. Kumafilimu e-epitaxial ajiyile, lokhu kucindezeleka kungabangela ukuqhekeka kwefilimu noma ngisho ne-substrate;
✔ Uma kuqhathaniswa nezinye izinto ezisetshenziswayo, ukuhanjiswa kokushisa kwezinto ezisetshenziswayo zesafire kuphansi (cishe ku-0.25W*cm-1*K-1 ku-100℃), futhi ukusebenza kokushabalalisa ukushisa kubi;
✔ Ngenxa yokungasebenzi kahle kwayo, ama-sapphire substrates awakwazi ukuhlanganiswa nokusetshenziswa kwawo namanye amadivayisi e-semiconductor.
Nakuba ubuningi bezingqimba ze-GaN epitaxial ezikhuliswe kuma-substrate e-sapphire buphezulu, kubonakala sengathi akunciphisi kakhulu ukusebenza kwe-optoelectronic kwama-LED aluhlaza okwesibhakabhaka noluhlaza okwesibhakabhaka asekelwe ku-GaN, ngakho-ke ama-substrate e-sapphire asasetshenziswa kakhulu kuma-LED asekelwe ku-GaN.
Ngokuthuthukiswa kwezinhlelo zokusebenza ezintsha zamadivayisi e-GaN njenge-laser noma amanye amadivayisi wamandla aphezulu, amaphutha angokwemvelo ezingxenye ze-sapphire aseye aba umkhawulo ekusetshenzisweni kwawo. Ngaphezu kwalokho, ngokuthuthukiswa kobuchwepheshe bokukhula kwezingxenye ze-SiC, ukunciphisa izindleko kanye nokuvuthwa kobuchwepheshe be-GaN epitaxial kuma-substrate e-Si, ucwaningo olwengeziwe mayelana nokukhulisa izendlalelo ze-GaN epitaxial kuma-substrate e-sapphire luye lwabonisa kancane kancane ukuthambekela kokupholisa.
I-GaN epitaxy ku-SiC
Uma kuqhathaniswa ne-sapphire, ama-substrate e-SiC (amakristalu angu-4H- kanye no-6H) anokungalingani okuncane kwe-lattice nama-GaN epitaxial layers (3.1%, okulingana namafilimu e-epitaxial aqondiswe ku-[0001], ukuqhutshwa kokushisa okuphezulu (cishe u-3.8W*cm-1*K-1), njll. Ngaphezu kwalokho, ukuqhutshwa komoya kwama-substrate e-SiC kuvumela nokuxhumana kukagesi ukuthi kwenziwe ngemuva kwe-substrate, okusiza ukwenza lula isakhiwo sedivayisi. Ukuba khona kwalezi zinzuzo kudonsele abacwaningi abaningi ukuba basebenze ku-GaN epitaxy kuma-substrate e-silicon carbide.
Kodwa-ke, ukusebenza ngqo kuma-substrate e-SiC ukuze ugweme ukukhulisa ama-epilayers e-GaN nakho kubhekene nochungechunge lwezinkinga, okuhlanganisa okulandelayo:
✔ Ubulukhuni bomphezulu be-substrates ze-SiC buphakeme kakhulu kunobe-substrates ze-sapphire (ubulukhuni be-sapphire 0.1nm RMS, ubulukhuni be-SiC 1nm RMS), ama-substrates e-SiC anobunzima obukhulu kanye nokusebenza kabi kokucubungula, futhi lobu bulukhuni kanye nomonakalo wokupholisha osele nakho kungenye yemithombo yeziphambeko kuma-epilayers e-GaN.
✔ Ubuningi bokuhlukaniswa kwezikulufo ze-SiC substrates buphezulu (ubuningi bokuhlukaniswa kwezikulufo bungu-103-104cm-2), ukuhlukaniswa kwezikulufo kungasakazeka ku-epilayer ye-GaN futhi kunciphise ukusebenza kwedivayisi;
✔ Ukuhlelwa kwe-athomu ebusweni be-substrate kubangela ukwakheka kwamaphutha okuhlanganisa (ama-BSF) ku-epilayer ye-GaN. Ku-epitaxial GaN kuma-substrate e-SiC, kunezindlela eziningi zokuhlelwa kwe-athomu ezingenzeka ku-substrate, okuholela ekuhleleni kokuqala kokuhlanganiswa kwe-athomu okungaguquki kwesendlalelo se-epitaxial GaN kuso, okuvame ukuba namaphutha okuhlanganisa. Amaphutha okuhlanganisa (ama-SF) angenisa amasimu kagesi akhelwe ngaphakathi ku-c-axis, okuholela ezinkingeni ezifana nokuvuza kwamadivayisi okuhlukanisa abathwali bendiza;
✔ I-coefficient yokwanda kokushisa kwe-substrate ye-SiC incane kuneye-AlN ne-GaN, okubangela ukunqwabelana kokucindezeleka kokushisa phakathi kwengqimba ye-epitaxial kanye ne-substrate ngesikhathi senqubo yokupholisa. UWaltereit noBrand babikezela ngokusekelwe emiphumeleni yabo yocwaningo ukuthi le nkinga ingancishiswa noma ixazululwe ngokukhuliswa kwezingqimba ze-epitaxial ze-GaN ezingqimbeni ze-nucleation ze-AlN ezincane, eziqinile;
✔ Inkinga yokungamanzi kahle kwama-athomu e-Ga. Lapho kukhuliswa izendlalelo ze-epitaxial ze-GaN ngqo ebusweni be-SiC, ngenxa yokungamanzi kahle phakathi kwama-athomu amabili, i-GaN ithambekele ekukhuleni kwesiqhingi se-3D ebusweni be-substrate. Ukwethula ungqimba lwe-buffer kuyisisombululo esivame ukusetshenziswa kakhulu ukuthuthukisa ikhwalithi yezinto ze-epitaxial ku-epitaxy ye-GaN. Ukwethula ungqimba lwe-buffer lwe-AlN noma i-AlxGa1-xN kungathuthukisa ngempumelelo ukumanzika kobuso be-SiC futhi kwenze ungqimba lwe-epitaxial lwe-GaN lukhule ngezinga ezimbili. Ngaphezu kwalokho, kungalawula nokucindezeleka futhi kuvimbele amaphutha e-substrate ukuthi adlulele ku-epitaxy ye-GaN;
✔ Ubuchwepheshe bokulungiselela ama-substrate e-SiC abukavuthwa, izindleko ze-substrate ziphezulu, futhi bambalwa abaphakeli futhi bancane kakhulu.
Ucwaningo lukaTorres nabanye lubonisa ukuthi ukuqopha i-substrate ye-SiC nge-H2 ekushiseni okuphezulu (1600°C) ngaphambi kwe-epitaxy kungakhiqiza isakhiwo sesinyathelo esihlelekile kakhulu ebusweni be-substrate, ngaleyo ndlela kutholakale ifilimu ye-AlN epitaxial esezingeni eliphezulu kunalapho ikhuliswe ngqo ebusweni be-substrate yokuqala. Ucwaningo lukaXie nethimba lakhe luphinde lubonise ukuthi ukuqopha ngaphambi kokwelashwa kwe-substrate ye-silicon carbide kungathuthukisa kakhulu isimo sobuso kanye nekhwalithi yekristalu yengqimba ye-GaN epitaxial. USmith nabanye bathole ukuthi ukuhlukaniswa kwentambo okuvela kungqimba ye-substrate/buffer kanye ne-buffer layer/epitaxial layer interfaces kuhlobene nokuthamba kwe-substrate [5].
Umfanekiso 4 Isimo se-TEM samasampula e-GaN epitaxial layer akhuliswe ku-6H-SiC substrate (0001) ngaphansi kwezimo ezahlukene zokwelashwa kobuso (a) ukuhlanzwa kwamakhemikhali; (b) ukuhlanzwa kwamakhemikhali + ukwelashwa kwe-hydrogen plasma; (c) ukuhlanzwa kwamakhemikhali + ukwelashwa kwe-hydrogen plasma + ukwelashwa kokushisa kwe-hydrogen okungu-1300℃ imizuzu engama-30
I-GaN epitaxy ku-Si
Uma kuqhathaniswa ne-silicon carbide, i-sapphire nezinye izinto ezisetshenziswayo, inqubo yokulungiselela i-silicon substrate ivuthiwe, futhi ingahlinzeka ngokuzinzile ngezinto ezisetshenziswayo ezinkulu ezivuthiwe ngokusebenza okubiza kakhulu. Ngesikhathi esifanayo, ukuhanjiswa kokushisa kanye nokuhanjiswa kukagesi kuhle, kanti inqubo yedivayisi ye-Si electronic ivuthiwe. Amathuba okuhlanganisa ngokuphelele amadivayisi e-optoelectronic GaN namadivayisi kagesi e-Si esikhathini esizayo nawo enza ukukhula kwe-GaN epitaxy ku-silicon kukhange kakhulu.
Kodwa-ke, ngenxa yomehluko omkhulu kuma-lattice constants phakathi kwe-Si substrate nezinto ze-GaN, i-epitaxy engafani ye-GaN ku-Si substrate iyi-epitaxy enkulu engavamile yokungafani, futhi idinga ukubhekana nochungechunge lwezinkinga:
✔ Inkinga yamandla esibonakalayo sobuso. Lapho i-GaN ikhula ku-substrate ye-Si, ubuso be-substrate ye-Si buzoqala ngokufakwa i-nitride ukuze kwakheke ungqimba lwe-silicon nitride olungenawo ukwakheka kanye nokukhula kwe-GaN enobuningi obukhulu. Ngaphezu kwalokho, ubuso be-Si buzoqala buthinte i-Ga, ezokonakalisa ubuso be-substrate ye-Si. Emazingeni okushisa aphezulu, ukubola kobuso be-Si kuzosakazeka kungqimba lwe-GaN epitaxial ukuze kwakheke amabala amnyama e-silicon.
✔ Ukungafani okungaguquki kwe-lattice phakathi kwe-GaN ne-Si kukhulu (~17%), okuzoholela ekwakhekeni kokuhlukaniswa kwe-threading okunobuningi obukhulu futhi kunciphise kakhulu ikhwalithi yesendlalelo se-epitaxial;
✔ Uma kuqhathaniswa ne-Si, i-GaN ine-coefficient enkulu yokwandisa ukushisa (i-coefficient yokwandisa ukushisa kwe-GaN icishe ibe ngu-5.6×10-6K-1, i-coefficient yokwandisa ukushisa kwe-Si icishe ibe ngu-2.6×10-6K-1), futhi imifantu ingadalwa kungqimba lwe-epitaxial ye-GaN ngesikhathi sokupholisa izinga lokushisa le-epitaxial liye ekushiseni kwegumbi;
✔ I-Si isabela ne-NH3 emazingeni okushisa aphezulu ukuze yakhe i-polycrystalline SiNx. I-AlN ayikwazi ukwakha i-nucleus eqondiswe ngokukhethekile ku-polycrystalline SiNx, okuholela ekuqondeni okungahlelekile kwesendlalelo se-GaN esikhule kamuva kanye nenani elikhulu lamaphutha, okuholela ekhwalithini ephansi yekristalu yesendlalelo se-GaN epitaxial, kanye nobunzima bokwakha isendlalelo se-GaN epitaxial esisodwa [6].
Ukuze kuxazululwe inkinga yokungafani okukhulu kwe-lattice, abacwaningi bazame ukwethula izinto ezifana ne-AlAs, GaAs, AlN, GaN, ZnO, kanye ne-SiC njengezingqimba ze-buffer kuma-substrate e-Si. Ukuze kugwenywe ukwakheka kwe-polycrystalline SiNx futhi kuncishiswe imiphumela yayo emibi kwikhwalithi yekristalu yezinto ze-GaN/AlN/Si (111), i-TMAl ngokuvamile iyadingeka ukuthi yethulwe isikhathi esithile ngaphambi kokukhula kwe-epitaxial kwengqimba ye-buffer ye-AlN ukuvimbela i-NH3 ukuthi ingasabeli ebusweni be-Si obuveziwe ukuze kwakheke i-SiNx. Ngaphezu kwalokho, ubuchwepheshe be-epitaxial njengobuchwepheshe be-substrate obunamaphethini bungasetshenziswa ukuthuthukisa ikhwalithi yengqimba ye-epitaxial. Ukuthuthukiswa kwalezi zobuchwepheshe kusiza ukuvimbela ukwakheka kwe-SiNx esibonakalayo se-epitaxial, ukukhuthaza ukukhula okunezinhlangothi ezimbili kwengqimba ye-epitaxial ye-GaN, nokuthuthukisa ikhwalithi yokukhula kwengqimba ye-epitaxial. Ngaphezu kwalokho, kwethulwa isendlalelo se-buffer se-AlN ukuze kulungiswe ukucindezeleka kokudonsa okubangelwa umehluko kuma-coefficients okwandisa ukushisa ukuze kugwenywe imifantu kungqimba ye-epitaxial ye-GaN ku-substrate ye-silicon. Ucwaningo lukaKrost lubonisa ukuthi kukhona ubudlelwano obuhle phakathi kobukhulu besendlalelo se-AlN buffer kanye nokunciphisa ukucindezeleka. Lapho ubukhulu besendlalelo se-buffer bufika ku-12nm, isendlalelo se-epitaxial esinobukhulu obungaphezu kuka-6μm singatshalwa ku-substrate ye-silicon ngokusebenzisa uhlelo lokukhula olufanele ngaphandle kokuqhekeka kwesendlalelo se-epitaxial.
Ngemva kwemizamo yesikhathi eside yabacwaningi, ikhwalithi yezingqimba ze-epitaxial ze-GaN ezikhuliswe kuma-substrate e-silicon ithuthukisiwe kakhulu, futhi amadivayisi anjenge-field effect transistors, i-Schottky barrier ultraviolet detectors, i-LED eluhlaza okwesibhakabhaka kanye ne-ultraviolet lasers enze intuthuko enkulu.
Ngamafuphi, njengoba ama-substrate e-epitaxial e-GaN asetshenziswa kakhulu e-epitaxy engafani, wonke abhekene nezinkinga ezivamile ezifana nokungafani kwe-lattice kanye nomehluko omkhulu kuma-coefficients okwandisa ukushisa kuya emazingeni ahlukahlukene. Ama-substrate e-epitaxial e-GaN afanayo anqunyelwe ukuvuthwa kobuchwepheshe, futhi ama-substrate awakakhiqizwa ngobuningi. Izindleko zokukhiqiza ziphezulu, usayizi we-substrate mncane, futhi ikhwalithi ye-substrate ayifanele. Ukuthuthukiswa kwama-substrate amasha e-epitaxial e-GaN kanye nokuthuthukiswa kwekhwalithi ye-epitaxial kusengenye yezinto ezibalulekile ezivimbela intuthuko eyengeziwe yemboni ye-epitaxial ye-GaN.
IV. Izindlela ezivamile ze-GaN epitaxy
I-MOCVD (ukufakwa komphunga wamakhemikhali)
Kubonakala sengathi i-epitaxy efanayo kuma-substrate e-GaN iyisinqumo esingcono kakhulu se-epitaxy ye-GaN. Kodwa-ke, njengoba izandulela zokufakwa komphunga wamakhemikhali yi-trimethylgallium ne-ammonia, kanti igesi ethwalayo iyi-hydrogen, izinga lokushisa elijwayelekile lokukhula kwe-MOCVD licishe libe ngu-1000-1100℃, kanti izinga lokukhula le-MOCVD licishe libe ama-microns ambalwa ngehora. Ingakhiqiza ama-interfaces aqinile ezingeni le-athomu, elifanele kakhulu ukukhula kwe-heterojunctions, ama-quantum wells, ama-superlattice nezinye izakhiwo. Izinga layo lokukhula okusheshayo, ukufana okuhle, kanye nokufaneleka kokukhula kwendawo enkulu kanye nezingcezu eziningi kuvame ukusetshenziswa ekukhiqizweni kwezimboni.
I-MBE (i-molecular beam epitaxy)
Ku-epitaxy ye-molecular beam, i-Ga isebenzisa umthombo we-elemental, kanti i-nitrogen esebenzayo itholakala ku-nitrogen nge-RF plasma. Uma kuqhathaniswa nendlela ye-MOCVD, izinga lokushisa lokukhula kwe-MBE liphansi cishe ngo-350-400℃. Izinga lokushisa lokukhula eliphansi lingagwema ukungcola okuthile okungabangelwa izindawo ezinokushisa okuphezulu. Uhlelo lwe-MBE lusebenza ngaphansi kwe-vacuum ephezulu kakhulu, okuvumela ukuthi luhlanganise izindlela eziningi zokuthola indawo. Ngesikhathi esifanayo, izinga lokukhula kwalo kanye namandla okukhiqiza akunakuqhathaniswa ne-MOCVD, futhi lusetshenziswa kakhulu ocwaningweni lwesayensi [7].
Umfanekiso 5 (a) Uhlelo lwe-Eiko-MBE (b) uhlelo lwegumbi lokusabela eliyinhloko le-MBE
Indlela ye-HVPE (i-hydride vapor phase epitaxy)
Izinto ezandulela indlela ye-hydride vapor phase epitaxy yi-GaCl3 kanye ne-NH3. UDetchprohm nabanye basebenzise le ndlela ukukhulisa ungqimba lwe-epitaxial lwe-GaN olunamakhulu ama-microns obukhulu ebusweni be-substrate ye-sapphire. Ekuhlolweni kwabo, ungqimba lwe-ZnO lwakhuliswa phakathi kwe-substrate ye-sapphire kanye nongqimba lwe-epitaxial njengengqimba ye-buffer, kanti ungqimba lwe-epitaxial lwasuswa ebusweni be-substrate. Uma kuqhathaniswa ne-MOCVD kanye ne-MBE, isici esiyinhloko sendlela ye-HVPE yisilinganiso sayo sokukhula esiphezulu, esifanele ukukhiqizwa kwezingqimba ezijiyile kanye nezinto zobuningi. Kodwa-ke, lapho ubukhulu bengqimba ye-epitaxial budlula u-20μm, ungqimba lwe-epitaxial olukhiqizwa yile ndlela luvame ukuqhekeka.
I-Akira USUI yethule ubuchwepheshe be-substrate obunamaphethini obusekelwe kule ndlela. Baqale bakhulisa ungqimba oluncane lwe-GaN epitaxial oluyi-1-1.5μm ubukhulu ku-substrate ye-sapphire besebenzisa indlela ye-MOCVD. Ungqimba lwe-epitaxial lwaluqukethe ungqimba lwe-GaN buffer oluyi-20nm ubukhulu olukhuliswe ngaphansi kwezimo zokushisa eziphansi kanye nongqimba lwe-GaN olukhuliswe ngaphansi kwezimo zokushisa eziphakeme. Ngemuva kwalokho, ku-430℃, ungqimba lwe-SiO2 lwabekwa phezu kongqimba lwe-epitaxial, kwathi imivimbo yamafasitela yenziwa kufilimu ye-SiO2 nge-photolithography. Isikhala semigqa sasingu-7μm kanti ububanzi bemaski babusukela ku-1μm kuya ku-4μm. Ngemuva kwalokhu kuthuthukiswa, bathole ungqimba lwe-GaN epitaxial ku-substrate ye-sapphire engamasentimitha angu-2 ububanzi eyayingenamabala futhi ibushelelezi njengesibuko ngisho nalapho ubukhulu bukhuphuke baba ngamashumi noma ngisho namakhulu ama-micron. Ubuningi besici buncishisiwe kusuka ku-109-1010cm-2 wendlela yendabuko ye-HVPE kuya cishe ku-6×107cm-2. Baphinde baveza ocwaningweni ukuthi uma izinga lokukhula lidlula u-75μm/h, ubuso besampula buzoba buqinile [8].
Umfanekiso 6 I-Graphical Substrate Schematic
V. Isifinyezo kanye Nombono
Izinto ze-GaN zaqala ukuvela ngo-2014 lapho i-LED yesibani esiluhlaza okwesibhakabhaka iwina umklomelo weNobel kuFiziksi ngalowo nyaka, futhi yangena emkhakheni womphakathi wezinhlelo zokushaja okusheshayo emkhakheni we-elekthronikhi yabathengi. Eqinisweni, izinhlelo zokusebenza kuma-amplifiers kagesi namadivayisi e-RF asetshenziswa eziteshini zesisekelo ze-5G abantu abaningi abangaziboni nazo ziye zavela buthule. Eminyakeni yamuva nje, ukuphumelela kwamadivayisi kagesi e-automotive-grade asekelwe ku-GaN kulindeleke ukuthi kuvule amaphuzu amasha okukhula emakethe yezinhlelo zokusebenza zezinto ze-GaN.
Isidingo esikhulu semakethe ngokuqinisekile sizokhuthaza intuthuko yezimboni nobuchwepheshe obuhlobene ne-GaN. Ngokuvuthwa kanye nokuthuthukiswa kochungechunge lwezimboni oluhlobene ne-GaN, izinkinga ezibhekene nobuchwepheshe bamanje be-epitaxial be-GaN ekugcineni zizothuthukiswa noma zinqotshwe. Esikhathini esizayo, abantu ngokuqinisekile bazothuthukisa ubuchwepheshe obusha be-epitaxial kanye nezinketho ezinhle kakhulu ze-substrate. Ngaleso sikhathi, abantu bazokwazi ukukhetha ubuchwepheshe bocwaningo lwangaphandle obufanele kakhulu kanye ne-substrate yezimo ezahlukene zohlelo lokusebenza ngokuya ngezici zezimo zohlelo lokusebenza, futhi bakhiqize imikhiqizo eyenziwe ngokwezifiso encintisana kakhulu.
Isikhathi sokuthunyelwe: Juni-28-2024