Ukadaulo wokulitsa tirigu wokhazikika komanso kukula kwa epitaxial-Ⅱ

2. Kukula kwa filimu yopyapyala ya Epitaxial

Gawo lapansi limapereka gawo lothandizira kapena gawo loyendetsa magetsi pazida zamagetsi za Ga2O3. Gawo lotsatira lofunika ndi gawo la channel kapena gawo la epitaxial lomwe limagwiritsidwa ntchito polimbana ndi magetsi komanso kunyamula anthu. Pofuna kuwonjezera mphamvu ya magetsi yotayika komanso kuchepetsa mphamvu ya magetsi, makulidwe olamulirika ndi kuchuluka kwa doping, komanso ubwino wabwino wa zinthu, ndi zina zofunika. Magawo apamwamba a Ga2O3 epitaxial nthawi zambiri amaikidwa pogwiritsa ntchito molecular beam epitaxy (MBE), metal organic chemical vapor deposition (MOCVD), halide vapor deposition (HVPE), pulsed laser deposition (PLD), ndi njira zosungiramo zinthu pogwiritsa ntchito fog CVD.

Gome 2 Maukadaulo ena oyimira epitaxial

2.1 Njira ya MBE

Ukadaulo wa MBE umadziwika chifukwa cha luso lake lokulitsa mafilimu a β-Ga2O3 apamwamba, opanda chilema okhala ndi doping ya n-type yolamulidwa chifukwa cha malo ake otayira mpweya wambiri komanso kuyera kwambiri kwa zinthu. Zotsatira zake, wakhala umodzi mwa ukadaulo wodziwika bwino komanso wogulitsidwa kwambiri wa β-Ga2O3 thin film deposition. Kuphatikiza apo, njira ya MBE idakonzanso bwino mawonekedwe a heterostructure apamwamba kwambiri, otsika kwambiri a β-(AlXGa1-X)2O3/Ga2O3. MBE imatha kuyang'anira kapangidwe ka pamwamba ndi mawonekedwe ake nthawi yeniyeni pogwiritsa ntchito ma atomic layer molondola pogwiritsa ntchito reflection high energy electron diffraction (RHEED). Komabe, mafilimu a β-Ga2O3 omwe amakula pogwiritsa ntchito ukadaulo wa MBE akadali ndi mavuto ambiri, monga kukula kochepa komanso kukula kochepa kwa filimu. Kafukufukuyu adapeza kuti kukula kwake kunali mu dongosolo la (010)>(001)>(−201)>(100). Pansi pa kutentha pang'ono kwa Ga kwa 650 mpaka 750°C, β-Ga2O3 (010) imakula bwino kwambiri ndi malo osalala komanso kukula kwakukulu. Pogwiritsa ntchito njira iyi, β-Ga2O3 epitaxy idakwaniritsidwa bwino ndi RMS roughness ya 0.1 nm. β-Ga2O3 Mu malo olemera a Ga, mafilimu a MBE omwe amakula kutentha kosiyanasiyana akuwonetsedwa pachithunzichi. Novel Crystal Technology Inc. yapanga bwino ma wafer a 10 × 15mm2 β-Ga2O3MBE. Amapereka ma substrates a β-Ga2O3 single crystal apamwamba kwambiri (010) okhala ndi makulidwe a 500 μm ndi XRD FWHM pansi pa masekondi 150 arc. Substrateyo ndi Sn doped kapena Fe doped. Chitsulo choyendetsera mpweya cha Sn-doped chili ndi kuchuluka kwa doping kwa 1E18 mpaka 9E18cm−3, pomwe chitsulo choteteza mpweya cha iron-doped semi-insulating chili ndi resistivity yoposa 10E10 Ω cm.

2.2 Njira ya MOCVD

MOCVD imagwiritsa ntchito mankhwala achitsulo ngati zinthu zoyambira kumera mafilimu opyapyala, motero imapanga kupanga kwakukulu kwa malonda. Polima Ga2O3 pogwiritsa ntchito njira ya MOCVD, trimethylgallium (TMGa), triethylgallium (TEGa) ndi Ga (dipentyl glycol formate) nthawi zambiri amagwiritsidwa ntchito ngati gwero la Ga, pomwe H2O, O2 kapena N2O amagwiritsidwa ntchito ngati gwero la okosijeni. Kukula pogwiritsa ntchito njira iyi nthawi zambiri kumafuna kutentha kwambiri (>800°C). Ukadaulo uwu uli ndi kuthekera kopeza kuchuluka kochepa kwa chonyamulira komanso kuyenda kwa ma elekitironi kutentha kwambiri komanso kochepa, kotero ndikofunikira kwambiri pakukwaniritsa zida zamagetsi za β-Ga2O3 zogwira ntchito kwambiri. Poyerekeza ndi njira yokulira ya MBE, MOCVD ili ndi mwayi wopeza kuchuluka kwakukulu kwa mafilimu a β-Ga2O3 chifukwa cha mawonekedwe a kukula kwa kutentha kwambiri komanso zochita za mankhwala.

Chithunzi 7 β-Ga2O3 (010) AFM chithunzi

Chithunzi 8 β-Ga2O3 Ubale pakati pa μ ndi kukana kwa pepala komwe kumayesedwa ndi Hall ndi kutentha

2.3 Njira ya HVPE

HVPE ndi ukadaulo wa epitaxial wokhwima ndipo wakhala ukugwiritsidwa ntchito kwambiri pakukula kwa epitaxial kwa ma semiconductors a III-V. HVPE imadziwika ndi mtengo wake wotsika wopanga, kukula kwake mwachangu, komanso makulidwe ake apamwamba a filimu. Tiyenera kudziwa kuti HVPEβ-Ga2O3 nthawi zambiri imakhala ndi mawonekedwe ozungulira pamwamba komanso kuchuluka kwa zolakwika pamwamba ndi mabowo. Chifukwa chake, njira zopangira mankhwala ndi makina ndizofunikira musanapange chipangizocho. Ukadaulo wa HVPE wa epitaxy ya β-Ga2O3 nthawi zambiri umagwiritsa ntchito GaCl ndi O2 ya gasi ngati zoyambira kuti zilimbikitse kutentha kwambiri kwa matrix ya (001) β-Ga2O3. Chithunzi 9 chikuwonetsa momwe pamwamba ndi kukula kwa filimu ya epitaxial kumakhudzira kutentha. M'zaka zaposachedwa, Novel Crystal Technology Inc. yaku Japan yapambana kwambiri pamalonda mu HVPE homoepitaxial β-Ga2O3, yokhala ndi makulidwe a epitaxial layer a 5 mpaka 10 μm ndi kukula kwa wafer wa mainchesi 2 ndi 4. Kuphatikiza apo, ma wafer a HVPE β-Ga2O3 homoepitaxial okwana 20 μm okoka opangidwa ndi China Electronics Technology Group Corporation nawonso alowa mu gawo la malonda.

Chithunzi 9 Njira ya HVPE β-Ga2O3

2.4 Njira ya PLD

Ukadaulo wa PLD umagwiritsidwa ntchito makamaka poika mafilimu ovuta a oxide ndi ma heterostructures. Panthawi ya kukula kwa PLD, mphamvu ya photon imalumikizidwa ndi chinthu chomwe chikufunidwa kudzera mu njira yotulutsa ma electron. Mosiyana ndi MBE, tinthu ta PLD timapangidwa ndi kuwala kwa laser komwe kumakhala ndi mphamvu zambiri (>100 eV) kenako nkuyikidwa pa substrate yotentha. Komabe, panthawi ya ablation, tinthu tina tamphamvu kwambiri timakhudza mwachindunji pamwamba pa chinthucho, ndikupanga zolakwika za mfundo ndikuchepetsa mtundu wa filimuyo. Mofanana ndi njira ya MBE, RHEED ingagwiritsidwe ntchito kuyang'anira kapangidwe ka pamwamba ndi mawonekedwe a chinthucho nthawi yeniyeni panthawi ya PLD β-Ga2O3 deposition process, zomwe zimathandiza ofufuza kupeza molondola chidziwitso cha kukula. Njira ya PLD ikuyembekezeka kukulitsa mafilimu a β-Ga2O3 oyenda bwino kwambiri, zomwe zimapangitsa kuti ikhale yankho labwino kwambiri la ohmic contact mu zida zamagetsi za Ga2O3.

Chithunzi 10 cha AFM cha Si doped Ga2O3

2.5 Njira ya MIST-CVD

MIST-CVD ndi ukadaulo wosavuta komanso wotsika mtengo wokulitsa filimu yopyapyala. Njira ya CVD iyi imaphatikizapo kupopera mankhwala oyambira a atomu pa substrate kuti akwaniritse kuyika filimu yopyapyala. Komabe, mpaka pano, Ga2O3 yomwe imalimidwa pogwiritsa ntchito mist CVD ikadalibe mphamvu zamagetsi zabwino, zomwe zimasiya malo ambiri oti zinthu zikonzedwe bwino mtsogolo.