1. Ama-semiconductors esizukulwane sesithathu
Ubuchwepheshe besizukulwane sokuqala se-semiconductor bathuthukiswa ngokusekelwe ezintweni ezisetshenziswayo ezifana ne-Si ne-Ge. Kuyisisekelo esibonakalayo sokuthuthukiswa kwama-transistors kanye nobuchwepheshe besifunda esihlanganisiwe. Izinto ze-semiconductor zesizukulwane sokuqala zabeka isisekelo semboni ye-elekthronikhi ekhulwini lama-20 futhi ziyizinto eziyisisekelo zobuchwepheshe besekethe obuhlanganisiwe.
Izinto ze-semiconductor yesizukulwane sesibili ikakhulukazi zifaka i-gallium arsenide, i-indium phosphide, i-gallium phosphide, i-indium arsenide, i-aluminium arsenide nezinhlanganisela zazo ze-ternary. Izinto ze-semiconductor zesizukulwane sesibili ziyisisekelo semboni yolwazi ye-optoelectronic. Ngalesi sisekelo, izimboni ezihlobene ezifana nezibani, isibonisi, i-laser, nama-photovoltaics ziye zathuthukiswa. Zisetshenziswa kabanzi kubuchwepheshe bolwazi besimanje kanye nezimboni zokubonisa i-optoelectronic.
Izinto ezimelela izinto ze-semiconductor yesizukulwane sesithathu zifaka i-gallium nitride ne-silicon carbide. Ngenxa yegebe lebhendi elibanzi, isivinini sokukhukhuleka kwama-electron aphezulu, ukushintshwa kwe-thermal ephezulu, namandla enkundla ephukile, ziyizinto ezisetshenziswayo zokulungiselela ukuminyana kwamandla aphezulu, imvamisa ephezulu, kanye namadivayisi kagesi alahlekelwa kancane. Phakathi kwazo, amadivaysi kagesi e-silicon carbide anezinzuzo zokuminyana kwamandla aphezulu, ukusetshenziswa kwamandla aphansi, nosayizi omncane, futhi anamathemba abanzi okusebenza ezimotweni zamandla amasha, ama-photovoltaics, ezokuthutha ngesitimela, idatha enkulu, neminye imikhakha. Amadivayisi we-Gallium nitride RF anezinzuzo zokuvama okuphezulu, amandla aphezulu, umkhawulokudonsa obanzi, ukusetshenziswa kwamandla okuphansi kanye nosayizi omncane, futhi anamathemba okusebenza abanzi ekuxhumaneni kwe-5G, i-Inthanethi Yezinto, i-radar yezempi nezinye izinkambu. Ngaphezu kwalokho, amadivaysi asekelwe ku-gallium nitride asesetshenziswe kabanzi emkhakheni we-low-voltage. Ngaphezu kwalokho, eminyakeni yamuva nje, izinto ezisafufusa ze-gallium oxide kulindeleke ukuthi zenze ukuhambisana kobuchwepheshe nobuchwepheshe obukhona be-SiC ne-GaN, futhi zibe nethuba lokufaka isicelo ezindaweni eziphansi-frequency kanye ne-high-voltage.
Uma kuqhathaniswa nezinto zokwakha ze-semiconductor yesizukulwane sesibili, izinto zokwakha ze-semiconductor yesizukulwane sesithathu zinobubanzi be-bandgap ebanzi (ububanzi be-bandgap be-Si, into evamile yempahla ye-semiconductor yesizukulwane sokuqala, cishe i-1.1eV, ububanzi be-bandgap ye-GaAs, ejwayelekile impahla yesizukulwane sesibili semiconductor impahla, cishe 1.42eV, futhi ububanzi bandgap GaN, impahla ejwayelekile yesizukulwane sesithathu semiconductor impahla, ingaphezu 2.3eV), okuqinile ukumelana emisebeni, ukumelana okunamandla ukuwohloka insimu kagesi, futhi ukumelana nokushisa okuphezulu. Izinto ze-semiconductor yesizukulwane sesithathu ezinobubanzi be-bandgap ebanzi zifaneleka ngokukhethekile ukukhiqizwa kwamadivayisi we-elekthronikhi angavimbeli, ama-high-frequency, amandla aphezulu kanye nokuhlanganisa okuphezulu-ukuminyana. Ukusetshenziswa kwabo emishinini yefrikhwensi yomsakazo we-microwave, ama-LED, ama-laser, izinto zikagesi neminye imikhakha kudonse ukunaka okukhulu, futhi babonise amathemba entuthuko ebanzi kwezokuxhumana ngomakhalekhukhwini, amagridi ahlakaniphile, ezokuthutha ngojantshi, izimoto ezintsha zamandla, izinto zikagesi ezithengwayo, kanye ne-ultraviolet ne-blue. -amadivayisi okukhanya okuluhlaza [1].
Umthombo wesithombe: CASA, Zheshang Securities Research Institute
Umfanekiso 1 Isikali sesikhathi sedivayisi ye-GaN kanye nesibikezelo
II GaN isakhiwo impahla kanye nezici
I-GaN iyi-semiconductor ye-bandgap eqondile. Ububanzi be-bandgap besakhiwo se-wurtzite ekamelweni lokushisa cishe yi-3.26eV. Izinto ze-GaN zinezinhlaka ezintathu zekristalu eziyinhloko, okuyisakhiwo se-wurtzite, isakhiwo se-sphalerite kanye nesakhiwo sikasawoti wedwala. Phakathi kwabo, isakhiwo se-wurtzite yisakhiwo esizinzile kakhulu se-crystal. Umfanekiso wesi-2 wumdwebo wesakhiwo se-wurtzite esiyi-hexagonal se-GaN. Isakhiwo se-wurtzite sezinto ze-GaN singokwesakhiwo esivaleleke esinezinhlangothi ezine. Iyunithi ngayinye yeseli inama-athomu angu-12, okuhlanganisa ama-athomu angu-6 N nama-athomu angu-6 we-Ga. I-athomu ngayinye ye-Ga (N) yenza ibhondi nama-athomu angu-4 aseduze we-N (Ga) futhi inqwabelene ngokulandelana kwe-ABABAB… eduze [0001] indlela [2].
Umfanekiso 2 Isakhiwo se-Wurtzite I-GaN crystal cell diagram
III Ama-substrates asetshenziswa kakhulu e-GaN epitaxy
Kubonakala sengathi i-epitaxy efanayo kuma-substrates e-GaN iyinketho engcono kakhulu ye-GaN epitaxy. Kodwa-ke, ngenxa yamandla amakhulu ebhondi ye-GaN, lapho izinga lokushisa lifinyelela endaweni yokuncibilika engu-2500 ℃, ingcindezi ehambisanayo yokubola icishe ibe ngu-4.5GPa. Uma ingcindezi yokubola iphansi kunalokhu kucindezela, i-GaN ayincibiliki kodwa ibola ngokuqondile. Lokhu kwenza ubuchwepheshe bokulungiselela i-substrate evuthiwe efana nendlela ye-Czochralski ingafaneleki ukulungiswa kwe-GaN single crystal substrates, okwenza ama-GaN substrates abe nzima ukukhiqiza ngobuningi futhi abize. Ngakho-ke, ama-substrates avame ukusetshenziswa ekukhuleni kwe-GaN epitaxial ikakhulukazi i-Si, i-SiC, isafire, njll. [3].
Ishadi 3 GaN namapharamitha wezinto ezisetshenziswa kakhulu ze-substrate
I-GaN epitaxy kusafire
I-Sapphire inamakhemikhali azinzile, ishibhile, futhi inokuvuthwa okuphezulu kwemboni yokukhiqiza enkulu. Ngakho-ke, isibe enye yezinto zokuqala futhi ezisetshenziswa kakhulu ze-substrate kubunjiniyela bedivayisi ye-semiconductor. Njengenye yezindawo ezisetshenziswa kakhulu ze-GaN epitaxy, izinkinga ezinkulu ezidinga ukuxazululwa ngama-sapphire substrates yilezi:
✔ Ngenxa yokungafani kwe-lattice enkulu phakathi kwesafire (Al2O3) ne-GaN (cishe u-15%), ukuminyana kokukhubazeka kusixhumi esibonakalayo esiphakathi kongqimba lwe-epitaxial ne-substrate kuphezulu kakhulu. Ukuze kuncishiswe imiphumela yayo emibi, i-substrate kufanele ibe ngaphansi kokwelashwa okuyinkimbinkimbi ngaphambi kokuba inqubo ye-epitaxy iqale. Ngaphambi kokukhulisa i-GaN epitaxy kuma-sapphire substrates, indawo engaphansi kufanele iqale ihlanzwe ngokuqinile ukuze kukhishwe ukungcola, umonakalo osele wokupholisha, njll., futhi kukhiqizwe izinyathelo kanye nezinyathelo ezingaphezulu kwezakhiwo. Khona-ke, i-substrate surface i-nitrided ukushintsha izakhiwo zokumanzisa ungqimba lwe-epitaxial. Okokugcina, ungqimba oluncane lwebhafa ye-AlN (ngokuvamile engu-10-100nm ubukhulu) ludinga ukufakwa endaweni engaphansi futhi lufakwe endaweni yokushisa ephansi ukuze kulungiselelwe ukukhula kokugcina kwe-epitaxial. Noma kunjalo, ukuminyana kwe-dislocation kumafilimu e-GaN epitaxial atshalwe ku-sapphire substrates kusephezulu kunaleyo yamafilimu e-homoepitaxial (cishe u-1010cm-2, uma kuqhathaniswa ne-zero dislocation density kumafilimu e-silicon homoepitaxial noma i-gallium arsenide homoepitaxial films2-cm2, noma phakathi kuka-10 cm no-10 cm. 2). Ukuminyana okuphezulu kwesici kunciphisa ukuhamba kwenkampani yenethiwekhi, ngaleyo ndlela kufinyeze impilo yenkampani yenethiwekhi encane futhi kunciphise ukuqhutshwa kokushisa, konke okuzonciphisa ukusebenza kwedivayisi [4];
✔ I-thermal expansion coefficient yesafire inkulu kunaleyo ye-GaN, ngakho-ke i-biaxial compressive stress izokwenziwa kungqimba lwe-epitaxial phakathi nenqubo yokupholisa kusukela kuzinga lokushisa lokubeka kuya kuzinga lokushisa legumbi. Kumafilimu e-epitaxial aminyene, lokhu kucindezeleka kungabangela ukuqhekeka kwefilimu noma ngisho ne-substrate;
✔ Uma kuqhathaniswa namanye ama-substrates, i-thermal conductivity ye-sapphire substrates iphansi (cishe i-0.25W*cm-1*K-1 ku-100℃), futhi ukusebenza kokukhipha ukushisa kubi;
✔ Ngenxa yokungahambi kahle kwayo, ama-sapphire substrates awahambisani nokuhlanganiswa kwawo nokusebenza namanye amadivaysi e-semiconductor.
Nakuba ukuminyana kwesici sezendlalelo ze-GaN epitaxial ezitshalwe kuma-sapphire substrates kuphezulu, akubonakali kunciphisa kakhulu ukusebenza kwe-optoelectronic kwama-LED asekelwe ku-GaN aluhlaza okwesibhakabhaka, ngakho-ke ama-sapphire substrates asasetshenziswa ngokujwayelekile ama-LED asekelwe ku-GaN.
Ngokuthuthukiswa kwezinhlelo zokusebenza eziningi ezintsha zamadivayisi we-GaN njengama-lasers noma amanye amadivaysi amandla asondelene kakhulu, ukukhubazeka okungokwemvelo kwama-sapphire substrates kuye kwaba umkhawulo ekusetshenzisweni kwawo. Ukwengeza, ngokuthuthukiswa kobuchwepheshe bokukhula kwe-substrate ye-SiC, ukuncishiswa kwezindleko kanye nokuvuthwa kobuchwepheshe be-GaN epitaxial kuma-Si substrates, ucwaningo olwengeziwe mayelana nezingqimba ezikhulayo ze-GaN epitaxial kuma-sapphire substrates luye lwabonisa kancane kancane umkhuba wokupholisa.
I-GaN epitaxy ku-SiC
Uma kuqhathaniswa nesafire, ama-substrates e-SiC (4H- kanye ne-6H-crystals) ane-lattice encane engahambisani nezendlalelo ze-GaN epitaxial (3.1%, okulingana namafilimu e-epitaxial [0001] oriented), izinga eliphezulu le-thermal conductivity (cishe 3.8W*cm-1*K) -1), njll. Ngaphezu kwalokho, i-conductivity ye-SiC substrates iphinde ivumele ukuthintana kukagesi kwenziwe ngemuva kwe-substrate, okusiza ukwenza lula ukwakheka kwedivayisi. Ukuba khona kwalezi zinzuzo kuye kwaheha abacwaningi abaningi ngokwengeziwe ukuthi basebenze ku-GaN epitaxy kuma-silicon carbide substrates.
Kodwa-ke, ukusebenza ngokuqondile kuma-substrates e-SiC ukugwema ukukhulisa ama-epilayers e-GaN nakho kubhekana nochungechunge lokubi, okuhlanganisa nalokhu okulandelayo:
✔ Ubulukhuni obungaphezulu bama-substrates e-SiC buphakeme kakhulu kunobuka-sapphire substrates (ubunzima besafire 0.1nm RMS, i-SiC roughness 1nm RMS), ama-substrates e-SiC anobunzima obuphezulu nokusebenza kabi kokucubungula, futhi lobu bunzima kanye nomonakalo oyinsalela wokupholisha nakho kungenye yezinto imithombo yokukhubazeka kuma-epilayers e-GaN.
✔ I-screw dislocation density yama-SiC substrates iphezulu (i-dislocation density 103-104cm-2), ukukhishwa kwezikulufu kungase kusakaze ku-epilayer ye-GaN futhi kunciphise ukusebenza kwedivayisi;
✔ Ukuhlelwa kwe-athomu endaweni engaphansi kwe-substrate kubangela ukwakheka kwamaphutha okunqwabelanisa (ama-BSF) ku-epilayer ye-GaN. Ku-epitaxial GaN kuma-substrates e-SiC, kunama-oda amaningi angenzeka wokuhlelwa kwe-athomu ku-substrate, okuholela ekuhlelekeni kokunqwabelana kwe-athomu kokuqala okungahambisani kwesendlalelo se-epitaxial GaN kuso, esijwayele ukuba namaphutha ekustaki. Amaphutha okunqwabelanisa (ama-SF) angenisa izinkambu zikagesi ezakhelwe ngaphakathi eduze kwe-c-eksisi, okuholela ezinkingeni ezinjengokuvuza kwamadivayisi okuhlukanisa isithwali esisendizeni;
✔ I-thermal expansion coefficient ye-SiC substrate incane kunaleyo ye-AlN ne-GaN, ebangela ukunqwabelana kokucindezeleka okushisayo phakathi kongqimba lwe-epitaxial kanye ne-substrate phakathi nenqubo yokupholisa. U-Waltereit no-Brand babikezela ngokusekelwe emiphumeleni yabo yocwaningo ukuthi le nkinga ingadanjiswa noma ixazululwe ngokukhula kwezendlalelo ze-GaN epitaxial ezingqimbeni ze-nucleation ze-AlN ezizacile, ezicindezelwe ngokuhambisanayo;
✔ Inkinga yokungamanzi kahle kwama-athomu e-Ga. Lapho ikhula izingqimba ze-GaN epitaxial ngqo endaweni ye-SiC, ngenxa yokungenwa kahle kwamanzi phakathi kwama-athomu amabili, i-GaN ijwayele ukukhula kwesiqhingi se-3D endaweni engaphansi. Ukwethula isendlalelo se-buffer yisixazululo esisetshenziswa kakhulu sokuthuthukisa ikhwalithi yezinto ze-epitaxial ku-GaN epitaxy. Ukwethula isendlalelo sebhafa ye-AlN noma i-AlxGa1-xN kungathuthukisa ngempumelelo ukumanzisa kwendawo ye-SiC futhi kwenze isendlalelo se-GaN epitaxial sikhule ngezilinganiso ezimbili. Ngaphezu kwalokho, ingakwazi futhi ukulawula ukucindezeleka futhi ivimbele ukukhubazeka kwe-substrate kusukela ekudluleleni ku-GaN epitaxy;
✔ Ubuchwepheshe bokulungiselela ama-substrates e-SiC abuvuthiwe, izindleko ze-substrate ziphezulu, futhi kukhona abahlinzeki abambalwa kanye nokunikezwa okuncane.
Ucwaningo luka-Torres et al. lubonisa ukuthi ukufaka i-substrate ye-SiC ene-H2 ekushiseni okuphezulu (1600°C) ngaphambi kwe-epitaxy kungakhiqiza isakhiwo sesinyathelo esi-odelwe ngaphezulu endaweni engaphansi, ngaleyo ndlela kutholwe ifilimu yekhwalithi ephezulu ye-AlN epitaxial kunalapho iqondile. ikhule endaweni yokuqala ye-substrate. Ucwaningo lwe-Xie kanye nethimba lakhe luphinde lubonise ukuthi ukufakwa ngaphambili kwe-silicon carbide substrate kungathuthukisa ngokuphawulekayo i-morphology engaphezulu kanye nekhwalithi yekristalu ye-GaN epitaxial layer. Smith et al. ithole ukuthi ukuhlukaniswa kochungechunge okuvela kungqimba engaphansi/kusendlalelo sebhafa kanye nesendlalelo se-bafa/i-epitaxial layer ihlobene nokucaba kwe-substrate [5].
Umfanekiso 4 we-TEM morphology wamasampuli e-GaN epitaxial layer akhule ku-6H-SiC substrate (0001) ngaphansi kwezimo ezihlukene zokwelashwa kwendawo (a) ukuhlanzwa kwamakhemikhali; (b) ukuhlanza amakhemikhali + ukwelashwa kwe-hydrogen plasma; (c) ukuhlanza amakhemikhali + ukwelashwa kwe-hydrogen plasma + 1300℃ ukwelashwa kwe-hydrogen kwe-hydrogen imizuzu engama-30
I-GaN epitaxy ku-Si
Uma kuqhathaniswa ne-silicon carbide, isafire namanye ama-substrate, inqubo yokulungiselela i-silicon substrate ivuthiwe, futhi inganikeza ngokuzinzile ama-substrates anosayizi omkhulu avuthiwe ngokusebenza kwezindleko eziphezulu. Ngesikhathi esifanayo, i-thermal conductivity kanye ne-electrical conductivity kuhle, futhi inqubo ye-Si electronic device ivuthiwe. Amathuba okuhlanganisa ngokuphelele amadivaysi e-optoelectronic GaN nemishini kagesi ye-Si esikhathini esizayo futhi kwenza ukukhula kwe-GaN epitaxy ku-silicon kukhange kakhulu.
Kodwa-ke, ngenxa yomehluko omkhulu wama-lattice constants phakathi kwe-Si substrate ne-GaN material, i-heterogeneous epitaxy ye-GaN ku-Si substrate iyi-epitaxy enkulu evamile yokungafani, futhi idinga ukubhekana nochungechunge lwezinkinga:
✔ Inkinga yamandla esibonakalayo sobuso. Lapho i-GaN ikhula ku-Si substrate, ingaphezulu le-Si substrate lizoqala lifakwe i-nitrided ukuze kwakhe ungqimba lwe-amorphous silicon nitride olungahambisani ne-nucleation kanye nokukhula kwe-GaN ephezulu kakhulu. Ngaphezu kwalokho, i-Si surface izoqale ithinte i-Ga, ezogqwalisa ingaphezulu le-Si substrate. Emazingeni okushisa aphezulu, ukubola kwe-Si surface kuzosakazeka kungqimba lwe-GaN epitaxial ukuze kwakhe amabala amnyama e-silicon.
✔ Ukungafani okuqhubekayo kwe-lattice phakathi kwe-GaN ne-Si kukhulu (~17%), okuzoholela ekwakhekeni kwe-high-density threading dislocations futhi kunciphise kakhulu ikhwalithi ye-epitaxial layer;
✔ Uma kuqhathaniswa no-Si, i-GaN ine-coefficient yokwandisa ukushisa okukhudlwana (i-GaN's expansion coefficient imayelana no-5.6×10-6K-1, i-Si's expansion coefficient icishe ibe ngu-2.6×10-6K-1), futhi ukuqhekeka kungase kwenziwe ku-GaN ungqimba lwe-epitaxial ngesikhathi sokupholisa izinga lokushisa le-epitaxial ekamelweni lokushisa;
✔ I-Si isabela nge-NH3 emazingeni okushisa aphezulu ukuze yakhe i-polycrystalline SiNx. I-AlN ayikwazi ukwakha i-nucleus eqondiswe ngokukhethekile ku-polycrystalline SiNx, okuholela ekumeni okungahlelekile kwesendlalelo se-GaN esikhule kamuva kanye nenani eliphezulu lamaphutha, okuholela kukhwalithi yekristalu empofu ye-GaN epitaxial layer, ngisho nobunzima bokwenza i-crystalline eyodwa. I-GaN epitaxial layer [6].
Ukuze kuxazululwe inkinga yokungafani kwe-lattice enkulu, abacwaningi bazamile ukwethula izinto ezifana ne-AlAs, i-GaAs, i-AlN, i-GaN, i-ZnO, ne-SiC njengezendlalelo ze-buffer kuma-substrates e-Si. Ukuze ugweme ukwakheka kwe-polycrystalline SiNx futhi unciphise imiphumela yayo emibi kukhwalithi yekristalu yezinto ze-GaN/AlN/Si (111), i-TMAl ivame ukudingeka ukuthi yethulwe isikhathi esithile ngaphambi kokukhula kwe-epitaxial kwesendlalelo se-AlN sebhafa. ukuvimbela i-NH3 ukuthi isabele ngendawo engu-Si eveziwe ukuze yakhe i-SiNx. Ngaphezu kwalokho, ubuchwepheshe be-epitaxial obufana nobuchwepheshe be-substrate obunephethini bungasetshenziswa ukuthuthukisa ikhwalithi ye-epitaxial layer. Ukuthuthukiswa kwalobu buchwepheshe kusiza ukuvimbela ukwakheka kwe-SiNx kusixhumi esibonakalayo se-epitaxial, ukukhuthaza ukukhula okubili kwe-GaN epitaxial layer, nokuthuthukisa ikhwalithi yokukhula ye-epitaxial layer. Ukwengeza, isendlalelo sebhafa ye-AlN yethulwa ukuze kunxeshezelwe ukucindezeleka okuqinile okubangelwa umehluko kuma-coefficients wokunweba okushisayo ukuze kugwenywe imifantu kungqimba lwe-GaN epitaxial ku-silicon substrate. Ucwaningo luka-Krost lubonisa ukuthi kukhona ukuhlobana okuhle phakathi kogqinsi longqimba lwebhafa ye-AlN kanye nokuncipha kobunzima. Lapho ugqinsi lwesendlalelo se-buffer lufinyelela ku-12nm, ungqimba lwe-epitaxial olujiyile kuno-6μm lungatshalwa ku-silicon substrate ngohlelo olufanele lokukhula ngaphandle kokuqhekeka kongqimba lwe-epitaxial.
Ngemva kwemizamo yesikhathi eside yabacwaningi, ikhwalithi yezendlalelo ze-GaN epitaxial ezitshalwe kuma-silicon substrates iye yathuthukiswa kakhulu, futhi amadivayisi afana nama-transistors omphumela wensimu, ama-Schottky barrier ultraviolet detectors, ama-LED aluhlaza okwesibhakabhaka namalaser e-ultraviolet enze inqubekelaphambili ebalulekile.
Kafushane, njengoba ama-substrates e-GaN epitaxial asetshenziswa ngokuvamile eyi-epitaxy ehlukahlukene, wonke abhekana nezinkinga ezifanayo njengokungafani kwe-lattice kanye nomehluko omkhulu kuma-coefficients wokunweba okushisayo ukuya kumazinga ahlukahlukene. I-Homogeneous epitaxial GaN substrates inqunyelwe ukukhula kobuchwepheshe, futhi ama-substrates awakakhiqizwe ngobuningi. Izindleko zokukhiqiza ziphezulu, usayizi we-substrate mncane, futhi ikhwalithi ye-substrate ayilungile. Ukuthuthukiswa kwama-GaN epitaxial substrates amasha kanye nokuthuthukiswa kwekhwalithi ye-epitaxial kusengenye yezinto ezibalulekile ezivimbela ukuqhubeka kwemboni ye-GaN epitaxial.
IV. Izindlela ezijwayelekile ze-GaN epitaxy
I-MOCVD (i-chemical vapor deposition)
Kubonakala sengathi i-epitaxy ye-homogeneous kuma-substrates e-GaN iyinketho engcono kakhulu ye-GaN epitaxy. Kodwa-ke, njengoba izandulela ze-chemical vapor deposition yi-trimethylgallium ne-ammonia, kanti igesi ethwala i-hydrogen, izinga lokushisa elijwayelekile le-MOCVD lilinganiselwa ku-1000-1100℃, futhi izinga lokukhula kwe-MOCVD lingaba ama-microns ambalwa ngehora. Ingakhiqiza izindawo zokuhlangana eziphakeme ezingeni le-athomu, ezifanele kakhulu ukukhula kwama-heterojunctions, imithombo ye-quantum, ama-superlattice nezinye izakhiwo. Izinga lokukhula kwayo ngokushesha, ukufana okuhle, nokufaneleka kokukhula kwendawo enkulu kanye neziqephu eziningi kuvame ukusetshenziswa ekukhiqizweni kwezimboni.
I-MBE (i-molecular beam epitaxy)
Ku-epitaxy ye-molecular beam, i-Ga isebenzisa umthombo oyisisekelo, futhi i-nitrogen esebenzayo itholakala ku-nitrogen nge-RF plasma. Uma kuqhathaniswa nendlela ye-MOCVD, izinga lokushisa le-MBE licishe libe ngu-350-400℃ ngaphansi. Izinga lokushisa eliphansi lokukhula lingagwema ukungcoliswa okuthile okungase kubangelwe indawo yokushisa ephezulu. Isistimu ye-MBE isebenza ngaphansi kwe-vacuum ephezulu kakhulu, eyivumela ukuthi ihlanganise izindlela eziningi zokutholwa endaweni. Ngesikhathi esifanayo, izinga lokukhula kwayo namandla okukhiqiza angeke aqhathaniswe ne-MOCVD, futhi isetshenziswa 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)
Izandulela zendlela ye-hydride vapor phase epitaxy yi-GaCl3 ne-NH3. Detchprohm et al. isebenzise le ndlela ukuze ikhulise ungqimba lwe-GaN epitaxial oluwugqinsi olungamakhulu ama-microns ebusweni be-sapphire substrate. Ekuhloleni kwabo, ungqimba lwe-ZnO lwakhuliswa phakathi kwe-sapphire substrate kanye nongqimba lwe-epitaxial njengongqimba lwe-buffer, futhi ungqimba lwe-epitaxial lwaxebuka lwasuswa endaweni engaphansi. Uma kuqhathaniswa ne-MOCVD ne-MBE, isici esiyinhloko sendlela ye-HVPE izinga layo eliphezulu lokukhula, elifanele ukukhiqizwa kwezingqimba eziwugqinsi nezinto eziningi. Kodwa-ke, lapho ubukhulu bongqimba lwe-epitaxial budlula i-20μm, isendlalelo se-epitaxial esikhiqizwa yile ndlela sijwayele ukuqhekeka.
I-Akira USUI yethule ubuchwepheshe be-substrate obunephethini obususelwe kule ndlela. Baqale bakhula ungqimba oluncane lwe-GaN epitaxial engu-1-1.5μm oluncane endaweni engaphansi yesafire kusetshenziswa indlela ye-MOCVD. Ungqimba lwe-epitaxial lwaluhlanganisa ungqimba lwe-GaN oluwugqinsi oluwu-20nm olukhule ngaphansi kwezimo zokushisa eziphansi kanye nongqimba lwe-GaN olukhuliswe ngaphansi kwezimo zokushisa eziphezulu. Khona-ke, ku-430 ℃, ungqimba lwe-SiO2 lwalubekwe phezu kongqimba lwe-epitaxial, futhi imivimbo yamafasitela yenziwa kufilimu ye-SiO2 nge-photolithography. Isikhala semigqa sasingu-7μm futhi ububanzi bemaski busuka ku-1μm ukuya ku-4μm. Ngemva kwalokhu kuthuthukiswa, bathole isendlalelo se-GaN epitaxial ku-substrate yesafire engu-2-intshi enobubanzi obungaqhekeki futhi bushelelezi njengesibuko ngisho nalapho ugqinsi lukhuphukela amashumi noma ngisho namakhulu ama-microns. Ukuminyana kwesici kwehlisiwe kusuka ku-109-1010cm-2 yendlela ye-HVPE evamile kuya cishe ku-6×107cm-2. Baphinde baveza ekuhloleni ukuthi uma izinga lokukhula lidlula u-75μm/h, indawo yesampula izoba lukhuni[8].
Umfanekiso 6 we-Graphical Substrate Schematic
V. Isifinyezo kanye ne-Outlook
Izinto ze-GaN zaqala ukuvela ngo-2014 lapho ukukhanya okuluhlaza okwesibhakabhaka i-LED iwina uMklomelo KaNobel ku-Physics ngalowo nyaka, futhi ingena emkhakheni womphakathi wokushaja okusheshayo emkhakheni we-elekthronikhi yabathengi. Eqinisweni, izinhlelo zokusebenza ezikuma-amplifiers namadivayisi e-RF asetshenziswa eziteshini eziyisisekelo ze-5G abantu abaningi abangakwazi ukuzibona nazo ziye zavela buthule. Eminyakeni yakamuva, ukuphumelela kwemishini yamandla ebanga lezimoto esekwe ku-GaN kulindeleke ukuthi kuvule amaphuzu amasha okukhula emakethe yezicelo ze-GaN.
Isidingo esikhulu semakethe sizokhuthaza ukuthuthukiswa kwezimboni nobuchwepheshe obuhlobene ne-GaN. Ngokuvuthwa nokuthuthukiswa kochungechunge lwezimboni oluhlobene ne-GaN, izinkinga ezibhekene nobuchwepheshe bamanje be-GaN epitaxial ekugcineni zizothuthukiswa noma zinqotshwe. Ngokuzayo, abantu ngokuqinisekile bazothuthukisa ubuchwepheshe obusha be-epitaxial kanye nezinketho ezinhle kakhulu ze-substrate. Ngaleso sikhathi, abantu bazokwazi ukukhetha ubuchwepheshe bokucwaninga bangaphandle obufaneleka kakhulu kanye ne-substrate yezimo ezihlukene zohlelo lokusebenza ngokwezimpawu zezimo zohlelo lokusebenza, futhi bakhiqize imikhiqizo eyenziwe ngokwezifiso encintisana kakhulu.
Isikhathi sokuthumela: Jun-28-2024