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 I-GaN, into evamile yesizukulwane sesithathu se-semiconductor material, ingaphezu kuka-2.3eV), ukumelana nokukhanya okuqinile emisebeni, ukumelana okuqinile nokuwohloka kwensimu kagesi, nokumelana 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 ibuye ivumele ukuthintana kukagesi kwenziwe ngemuva kwe-substrate, esiza 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 ukukhula kwama-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-heterogeneous epitaxy, 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 efanayo 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 kwendawo enkulu kanye nokukhula kwezingxenye 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