1. Nā semiconductors hanauna ʻekolu
Ua hoʻomohala ʻia ka ʻenehana semiconductor hanauna mua ma muli o nā mea semiconductor e like me Si a me Ge. ʻO ia ke kumu waiwai no ka hoʻomohala ʻana i nā transistors a me ka ʻenehana kaapuni hoʻohui. Ua hoʻokumu nā mea semiconductor hanauna mua i ke kahua no ka ʻoihana uila i ke kenekulia 20 a ʻo ia nā mea kumu no ka ʻenehana kaapuni hoʻohui.
ʻO nā mea semiconductor hanauna ʻelua ka mea nui e komo pū me ka gallium arsenide, indium phosphide, gallium phosphide, indium arsenide, alumini arsenide a me kā lākou mau hui ternary. ʻO nā mea semiconductor hanauna ʻelua ke kumu o ka ʻoihana ʻike optoelectronic. Ma kēia kumu, ua hoʻomohala ʻia nā ʻoihana pili e like me ke kukui, ka hōʻike, ka laser, a me nā photovoltaics. Hoʻohana nui ʻia lākou i ka ʻenehana ʻike o kēia wā a me nā ʻoihana hōʻike optoelectronic.
ʻO nā mea i koho ʻia no nā mea semiconductor hanauna ʻekolu e komo pū ana me ka gallium nitride a me ka silicon carbide. Ma muli o ko lākou ākea ākea, ka wikiwiki o ka electron saturation drift, ke alakaʻi wela kiʻekiʻe, a me ka ikaika o ke kahua breakdown kiʻekiʻe, he mau mea kūpono lākou no ka hoʻomākaukau ʻana i nā mea uila kiʻekiʻe-mana, alapine kiʻekiʻe, a me ka pohō haʻahaʻa. I waena o lākou, loaʻa i nā mea mana silicon carbide nā pono o ka nui o ka ikehu kiʻekiʻe, ka hoʻohana ʻana i ka ikehu haʻahaʻa, a me ka liʻiliʻi o ka nui, a he mau manaʻolana noi ākea i nā kaʻa ikehu hou, photovoltaics, ka halihali kaʻaahi, ka ʻikepili nui, a me nā kahua ʻē aʻe. Loaʻa i nā mea RF Gallium nitride nā pono o ke alapine kiʻekiʻe, ka mana kiʻekiʻe, ka bandwidth ākea, ka hoʻohana ʻana i ka mana haʻahaʻa a me ka liʻiliʻi o ka nui, a he mau manaʻolana noi ākea i nā kamaʻilio 5G, ka Pūnaewele o nā Mea, ka radar koa a me nā kahua ʻē aʻe. Eia kekahi, ua hoʻohana nui ʻia nā mea mana e pili ana i ka gallium nitride i ke kahua haʻahaʻa-voltage. Eia kekahi, i nā makahiki i hala iho nei, manaʻo ʻia nā mea gallium oxide e kū mai ana e hana i ka hoʻopihapiha ʻenehana me nā ʻenehana SiC a me GaN e kū nei, a he mau manaʻolana noi hiki ke loaʻa i nā kahua haʻahaʻa-alapine a me ke kiʻekiʻe-voltage.
Ke hoʻohālikelike ʻia me nā mea semiconductor hanauna ʻelua, ʻoi aku ka laulā o ka bandgap o nā mea semiconductor hanauna ʻekolu (ʻo ka laulā bandgap o Si, kahi mea maʻamau o ka mea semiconductor hanauna mua, ma kahi o 1.1eV, ʻo ka laulā bandgap o GaAs, kahi mea maʻamau o ka mea semiconductor hanauna ʻelua, ma kahi o 1.42eV, a ʻo ka laulā bandgap o GaN, kahi mea maʻamau o ka mea semiconductor hanauna ʻekolu, ma luna o 2.3eV), ʻoi aku ka ikaika o ke kūʻē ʻana i ka radiation, ʻoi aku ka ikaika o ke kūʻē ʻana i ka haki ʻana o ke kahua uila, a me ke kūʻē ʻana i ka mahana kiʻekiʻe. ʻO nā mea semiconductor hanauna ʻekolu me ka laulā bandgap ākea he kūpono loa ia no ka hana ʻana i nā mea uila e kūʻē i ka radiation, alapine kiʻekiʻe, mana kiʻekiʻe a me ka hoʻohui kiʻekiʻe. ʻO kā lākou hoʻohana ʻana i nā mea uila alapine microwave, nā LED, nā lasers, nā mea mana a me nā kahua ʻē aʻe ua huki nui i ka nānā ʻana, a ua hōʻike lākou i nā manaʻolana hoʻomohala ākea i nā kamaʻilio kelepona, nā pūnaewele akamai, ka transit kaʻaahi, nā kaʻa ikehu hou, nā mea uila mea kūʻai aku, a me nā mea kukui ultraviolet a me ka uliuli-ʻōmaʻomaʻo [1].
Puna kiʻi: CASA, Zheshang Securities Research Institute
Kiʻi 1 Ka pae manawa a me ka wānana o ka hāmeʻa mana GaN
ʻO ke ʻano a me nā ʻano o ka mea GaN II
He semiconductor bandgap pololei ʻo GaN. ʻO ka laulā bandgap o ke ʻano wurtzite ma ka mahana o ka lumi ma kahi o 3.26eV. ʻEkolu mau ʻano kristal nui ko nā mea GaN, ʻo ia hoʻi ke ʻano wurtzite, ke ʻano sphalerite a me ke ʻano paʻakai pōhaku. I waena o lākou, ʻo ke ʻano wurtzite ka ʻano kristal paʻa loa. ʻO ke Kiʻi 2 kahi kiʻikuhi o ke ʻano wurtzite hexagonal o GaN. No ke ʻano wurtzite o ka mea GaN kahi ʻano hexagonal i hoʻopaʻa ʻia. Loaʻa i kēlā me kēia cell unit he 12 mau ʻātoma, me 6 mau ʻātoma N a me 6 mau ʻātoma Ga. Hoʻokumu kēlā me kēia ʻātoma Ga (N) i kahi pilina me nā ʻātoma N (Ga) kokoke loa 4 a ua hoʻopaʻa ʻia ma ke ʻano o ABABAB… ma ke kuhikuhi [0001] [2].
Kiʻi 2 Kiʻikuhi pūnaewele kristal GaN o ke ʻano Wurtzite
III Nā substrates i hoʻohana pinepine ʻia no ka epitaxy GaN
Me he mea lā ʻo ka epitaxy homogeneous ma nā substrates GaN ke koho maikaʻi loa no ka epitaxy GaN. Eia nō naʻe, ma muli o ka ikehu hoʻopaʻa nui o GaN, i ka wā e hiki ai ka mahana i ka pae heheʻe o 2500 ℃, ʻo kona kaomi decomposition e pili ana ma kahi o 4.5GPa. Ke haʻahaʻa ke kaomi decomposition ma mua o kēia kaomi, ʻaʻole heheʻe ʻo GaN akā decompose pololei. ʻO kēia ka mea e kūpono ʻole ai nā ʻenehana hoʻomākaukau substrate makua e like me ke ʻano Czochralski no ka hoʻomākaukau ʻana o nā substrates kristal hoʻokahi GaN, e paʻakikī ai ka hana nui ʻana i nā substrates GaN a pipiʻi hoʻi. No laila, ʻo nā substrates i hoʻohana pinepine ʻia i ka ulu ʻana o GaN epitaxial ʻo Si, SiC, sapphire, etc. [3].
Pakuhi 3 GaN a me nā palena o nā mea substrate i hoʻohana pinepine ʻia
ʻO ka epitaxy GaN ma ka sapeiro
He paʻa nā waiwai kemika o ka Sapphire, he makepono ke kumu kūʻai, a he kiʻekiʻe kona oʻo ʻana i ka ʻoihana hana nui. No laila, ua lilo ia i hoʻokahi o nā mea substrate mua loa a hoʻohana nui ʻia i ka ʻenekinia hāmeʻa semiconductor. Ma ke ʻano he hoʻokahi o nā substrates i hoʻohana pinepine ʻia no GaN epitaxy, ʻo nā pilikia nui e pono e hoʻoponopono ʻia no nā substrates sapphire:
✔ Ma muli o ka nui o ka mismatch lattice ma waena o ka sapphire (Al2O3) a me GaN (ma kahi o 15%), kiʻekiʻe loa ka nui o ka hemahema ma ka interface ma waena o ka papa epitaxial a me ka substrate. I mea e hōʻemi ai i kona mau hopena maikaʻi ʻole, pono e hoʻomaʻamaʻa mua ʻia ka substrate ma mua o ka hoʻomaka ʻana o ke kaʻina hana epitaxy. Ma mua o ka ulu ʻana o ka GaN epitaxy ma nā substrates sapphire, pono e hoʻomaʻemaʻe pono ʻia ka ʻili o ka substrate e wehe i nā mea haumia, nā pōʻino polishing koena, a pēlā aku, a e hana i nā ʻanuʻu a me nā ʻano ʻili o ka ʻanuʻu. A laila, ua nitrided ʻia ka ʻili o ka substrate e hoʻololi i nā waiwai pulu o ka papa epitaxial. ʻO ka hope, pono e waiho ʻia kahi papa buffer AlN lahilahi (maʻamau he 10-100nm ka mānoanoa) ma ka ʻili o ka substrate a hoʻomehana ʻia i ka mahana haʻahaʻa e hoʻomākaukau no ka ulu hope loa o ka epitaxial. ʻOiai pēlā, ʻoi aku ka kiʻekiʻe o ka dislocation density i nā kiʻiʻoniʻoni epitaxial GaN i ulu ʻia ma nā substrates sapphire ma mua o nā kiʻiʻoniʻoni homoepitaxial (ma kahi o 1010cm-2, i hoʻohālikelike ʻia me ka zero dislocation density i nā kiʻiʻoniʻoni homoepitaxial silicon a i ʻole nā kiʻiʻoniʻoni homoepitaxial gallium arsenide, a i ʻole ma waena o 102 a me 104cm-2). ʻO ke kiʻekiʻe o ka defect density e hōʻemi ana i ka mobility carrier, no laila e hoʻopōkole ana i ke ola o ka mea lawe liʻiliʻi a e hōʻemi ana i ka thermal conductivity, ʻo ia mau mea āpau e hōʻemi ai i ka hana o ka hāmeʻa [4];
✔ ʻOi aku ka nui o ke koina hoʻonui wela o ka sapphire ma mua o GaN, no laila e hoʻoulu ʻia ke koʻikoʻi compressive biaxial i loko o ka papa epitaxial i ke kaʻina hana o ka hoʻomaʻalili ʻana mai ka mahana deposition a i ka mahana o ka lumi. No nā kiʻiʻoniʻoni epitaxial mānoanoa, hiki i kēia koʻikoʻi ke kumu o ka haki ʻana o ke kiʻiʻoniʻoni a i ʻole ke substrate;
✔ Ke hoʻohālikelike ʻia me nā substrates ʻē aʻe, ʻoi aku ka haʻahaʻa o ka conductivity thermal o nā substrates sapphire (ma kahi o 0.25W * cm-1 * K-1 ma 100 ℃), a ʻaʻole maikaʻi ka hana hoʻopuehu wela;
✔ Ma muli o kona conductivity haʻahaʻa, ʻaʻole kūpono nā substrates sapphire i kā lākou hoʻohui a me ka hoʻohana ʻana me nā mea semiconductor ʻē aʻe.
ʻOiai ke kiʻekiʻe o ka nui o nā kīnā o nā papa epitaxial GaN i ulu ʻia ma nā substrates sapphire, ʻaʻole ia e hōʻemi nui i ka hana optoelectronic o nā LED polū-ʻōmaʻomaʻo e pili ana iā GaN, no laila he mau substrates maʻamau ka hoʻohana ʻia ʻana o nā substrates sapphire no nā LED e pili ana iā GaN.
Me ka hoʻomohala ʻana o nā noi hou aʻe o nā mea hana GaN e like me nā lasers a i ʻole nā mea hana mana kiʻekiʻe ʻē aʻe, ua lilo nā hemahema kūlohelohe o nā substrates sapphire i mea palena i kā lākou noi. Eia kekahi, me ka hoʻomohala ʻana o ka ʻenehana ulu substrate SiC, ka hoʻemi ʻana i ke kumukūʻai a me ka oʻo ʻana o ka ʻenehana epitaxial GaN ma nā substrates Si, ua hōʻike mālie ka noiʻi hou aku i ka ulu ʻana o nā papa epitaxial GaN ma nā substrates sapphire i kahi ʻano hoʻoluʻu.
ʻO ka epitaxy GaN ma SiC
Ke hoʻohālikelike ʻia me ka sapphire, ʻoi aku ka liʻiliʻi o ka lattice mismatch o nā substrates SiC (4H- a me 6H-crystals) me nā papa epitaxial GaN (3.1%, like me nā kiʻiʻoniʻoni epitaxial i kuhikuhi ʻia [0001], ʻoi aku ka kiʻekiʻe o ka conductivity thermal (ma kahi o 3.8W * cm-1 * K-1), a pēlā aku. Eia kekahi, ʻo ka conductivity o nā substrates SiC e ʻae pū i nā pilina uila e hana ʻia ma ke kua o ka substrate, kahi e kōkua ai i ka hoʻomaʻalahi ʻana i ke ʻano o ka hāmeʻa. ʻO ka loaʻa ʻana o kēia mau pono ua huki i nā mea noiʻi hou aʻe e hana ma GaN epitaxy ma nā substrates silicon carbide.
Eia nō naʻe, ʻo ka hana pololei ʻana ma nā substrates SiC e pale aku i ka ulu ʻana o nā epilators GaN e kū nei i kahi ʻano o nā hemahema, me kēia mau mea:
✔ ʻOi aku ke kiʻekiʻe o ka ʻili o nā substrates SiC ma mua o nā substrates sapphire (sapphire roughness 0.1nm RMS, SiC roughness 1nm RMS), he paʻakikī kiʻekiʻe ko nā substrates SiC a he hana hana maikaʻi ʻole, a ʻo kēia ʻino a me ke koena o ka polishing kekahi o nā kumu o nā hemahema i nā epilaiers GaN.
✔ Kiʻekiʻe ke kiʻekiʻe o ka dislocation o nā substrates SiC (dislocation density 103-104cm-2), hiki i nā dislocations o nā wili ke laha i ka GaN epilayer a hōʻemi i ka hana o ka hāmeʻa;
✔ ʻO ka hoʻonohonoho ʻana o ka atomika ma ka ʻili o ka substrate e hoʻoulu ai i ka hoʻokumu ʻia ʻana o nā hewa stacking (BSFs) i loko o ka GaN epilayer. No ka epitaxial GaN ma nā substrates SiC, aia kekahi mau kauoha hoʻonohonoho atomika ma ka substrate, e hopena ana i ke kauoha stacking atomika mua kūlike ʻole o ka papa epitaxial GaN ma luna, kahi i maʻalahi i nā hewa stacking. Hoʻokomo nā hewa stacking (SFs) i nā kahua uila i kūkulu ʻia ma ke axis c, e alakaʻi ana i nā pilikia e like me ka leakage o nā mea hoʻokaʻawale lawe mokulele;
✔ ʻOi aku ka liʻiliʻi o ke koina hoʻonui wela o ka substrate SiC ma mua o AlN a me GaN, kahi e hōʻiliʻili ai ke koʻikoʻi wela ma waena o ka papa epitaxial a me ka substrate i ka wā o ke kaʻina hoʻoluʻu. Ua wānana ʻo Waltereit lāua ʻo Brand ma muli o kā lākou mau hopena noiʻi e hiki ke hoʻomaha ʻia a hoʻoponopono ʻia paha kēia pilikia ma ka hoʻoulu ʻana i nā papa epitaxial GaN ma nā papa nucleation AlN lahilahi a ʻokoʻa hoʻi;
✔ ʻO ka pilikia o ka palupalu maikaʻi ʻole o nā ʻātoma Ga. Ke ulu pololei nei nā papa epitaxial GaN ma luna o ka ʻili SiC, ma muli o ka palupalu maikaʻi ʻole ma waena o nā ʻātoma ʻelua, ua maʻalahi ʻo GaN i ka ulu ʻana o ka mokupuni 3D ma luna o ka ʻili substrate. ʻO ka hoʻokomo ʻana i kahi papa buffer ka hopena i hoʻohana pinepine ʻia e hoʻomaikaʻi i ka maikaʻi o nā mea epitaxial ma GaN epitaxy. ʻO ka hoʻokomo ʻana i kahi papa buffer AlN a i ʻole AlxGa1-xN hiki ke hoʻomaikaʻi maikaʻi i ka palupalu o ka ʻili SiC a hoʻonui i ka papa epitaxial GaN i ʻelua mau ana. Eia kekahi, hiki iā ia ke hoʻoponopono i ke kaumaha a pale i nā hemahema substrate mai ka hoʻonui ʻana i ka epitaxy GaN;
✔ ʻAʻole i oʻo ka ʻenehana hoʻomākaukau o nā substrates SiC, kiʻekiʻe ke kumukūʻai o ka substrate, a he kakaikahi nā mea hoʻolako a me ka lako liʻiliʻi.
Ua hōʻike ʻia ka noiʻi a Torres et al. ʻo ke kālai ʻana i ka substrate SiC me H2 ma ke kiʻekiʻe o ka mahana (1600°C) ma mua o ka epitaxy hiki ke hana i kahi ʻano hana ʻanuʻu i hoʻonohonoho pono ʻia ma ka ʻili substrate, no laila e loaʻa ai kahi kiʻiʻoniʻoni epitaxial AlN kiʻekiʻe ma mua o ka wā i ulu pololei ʻia ai ma ka ʻili substrate mua. Ua hōʻike pū ʻia ka noiʻi a Xie a me kāna hui e hiki i ka etching pretreatment o ka substrate silicon carbide ke hoʻomaikaʻi nui i ke ʻano o ka ʻili a me ke ʻano kristal o ka papa epitaxial GaN. Ua ʻike ʻo Smith et al. ʻo nā dislocations threading e puka mai ana mai ka papa substrate/buffer a me nā interfaces papa buffer/epitaxial e pili ana i ka palahalaha o ka substrate [5].
Kiʻi 4 ʻAno TEM o nā laʻana papa epitaxial GaN i ulu ʻia ma ka substrate 6H-SiC (0001) ma lalo o nā kūlana mālama ʻili like ʻole (a) hoʻomaʻemaʻe kemika; (b) hoʻomaʻemaʻe kemika + mālama ʻana i ka plasma hydrogen; (c) hoʻomaʻemaʻe kemika + mālama ʻana i ka plasma hydrogen + 1300℃ mālama wela hydrogen no 30min
ʻO ka epitaxy GaN ma Si
Ke hoʻohālikelike ʻia me ka silicon carbide, sapphire a me nā substrates ʻē aʻe, ua oʻo ke kaʻina hana hoʻomākaukau substrate silicon, a hiki iā ia ke hāʻawi paʻa i nā substrates nui makua me ka hana kumukūʻai kiʻekiʻe. I ka manawa like, maikaʻi ka conductivity thermal a me ka conductivity uila, a ua oʻo ke kaʻina hana uila Si. ʻO ka hiki ke hoʻohui pono i nā polokalamu optoelectronic GaN me nā polokalamu uila Si i ka wā e hiki mai ana e hoʻolilo i ka ulu ʻana o GaN epitaxy ma silicon i mea hoihoi loa.
Eia nō naʻe, ma muli o ka ʻokoʻa nui o nā constants lattice ma waena o ka substrate Si a me ka mea GaN, ʻo ka epitaxy heterogeneous o GaN ma ka substrate Si he epitaxy mismatch nui maʻamau, a pono nō hoʻi e kū i kahi ʻano pilikia:
✔ Pilikia ka ikehu o ka ʻili. Ke ulu ʻo GaN ma luna o kahi substrate Si, e nitrided mua ʻia ka ʻili o ka substrate Si e hana i kahi papa nitride silicon amorphous ʻaʻole kūpono i ka nucleation a me ka ulu ʻana o GaN kiʻekiʻe. Eia kekahi, e hoʻopili mua ka ʻili Si iā Ga, ka mea e hōʻino i ka ʻili o ka substrate Si. I nā mahana kiʻekiʻe, e pālahalaha ka decomposition o ka ʻili Si i loko o ka papa epitaxial GaN e hana i nā kiko silicon ʻeleʻele.
✔ He nui ka mismatch constant lattice ma waena o GaN a me Si (~17%), kahi e alakaʻi ai i ka hoʻokumu ʻia ʻana o nā dislocations threading density kiʻekiʻe a hoʻemi nui i ka maikaʻi o ka papa epitaxial;
✔ Ke hoʻohālikelike ʻia me Si, ʻoi aku ka nui o ka coefficient hoʻonui wela o GaN (ʻo ka coefficient hoʻonui wela o GaN ma kahi o 5.6 × 10-6K-1, ʻo ka coefficient hoʻonui wela o Si ma kahi o 2.6 × 10-6K-1), a hiki ke hana ʻia nā māwae ma ka papa epitaxial GaN i ka wā e hoʻomaʻalili ai ka mahana epitaxial i ka mahana o ka lumi;
✔ Hoʻopili ʻo Si me NH3 i nā mahana kiʻekiʻe e hana i ka polycrystalline SiNx. ʻAʻole hiki iā AlN ke hana i kahi nucleus i kuhikuhi ʻia ma ka polycrystalline SiNx, kahi e alakaʻi ai i kahi kuhikuhi kūlike ʻole o ka papa GaN i ulu aʻe a me ka nui o nā hemahema, e hopena ana i ka maikaʻi ʻole o ka kristal o ka papa epitaxial GaN, a me ka paʻakikī i ka hana ʻana i kahi papa epitaxial GaN crystalline hoʻokahi [6].
I mea e hoʻoponopono ai i ka pilikia o ka mismatch lattice nui, ua hoʻāʻo nā mea noiʻi e hoʻolauna i nā mea e like me AlAs, GaAs, AlN, GaN, ZnO, a me SiC ma ke ʻano he mau papa buffer ma nā substrates Si. I mea e pale aku ai i ka hoʻokumu ʻia ʻana o ka polycrystalline SiNx a hoʻemi i kona hopena maikaʻi ʻole i ke ʻano kristal o nā mea GaN/AlN/Si (111), pono e hoʻolauna ʻia ʻo TMAl no kekahi manawa ma mua o ka ulu ʻana o ka epitaxial o ka papa buffer AlN e pale aku i ka NH3 mai ka pane ʻana me ka ʻili Si i hōʻike ʻia e hana iā SiNx. Eia kekahi, hiki ke hoʻohana ʻia nā ʻenehana epitaxial e like me ka ʻenehana substrate patterned e hoʻomaikaʻi i ka maikaʻi o ka papa epitaxial. Kōkua ka hoʻomohala ʻana o kēia mau ʻenehana i ka pale ʻana i ka hoʻokumu ʻia ʻana o SiNx ma ka interface epitaxial, e paipai i ka ulu ʻelua-dimensional o ka papa epitaxial GaN, a hoʻomaikaʻi i ka maikaʻi o ka ulu ʻana o ka papa epitaxial. Eia kekahi, ua hoʻolauna ʻia kahi papa buffer AlN e uku no ke koʻikoʻi tensile i hoʻokumu ʻia e ka ʻokoʻa o nā coefficients hoʻonui thermal e pale aku i nā māwae i ka papa epitaxial GaN ma ka substrate silicon. Ua hōʻike ʻia ka noiʻi a Krost aia kahi pilina maikaʻi ma waena o ka mānoanoa o ka papa buffer AlN a me ka emi ʻana o ke kaumaha. Ke hiki ka mānoanoa o ka papa buffer i 12nm, hiki ke ulu ʻia kahi papa epitaxial mānoanoa ma mua o 6μm ma kahi substrate silicon ma o kahi papahana ulu kūpono me ka ʻole o ka haki ʻana o ka papa epitaxial.
Ma hope o nā hana lōʻihi e nā mea noiʻi, ua hoʻomaikaʻi nui ʻia ke ʻano o nā papa epitaxial GaN i ulu ʻia ma nā substrates silicon, a ua holomua nui nā mea hana e like me nā transistors hopena kahua, nā mea ʻike ultraviolet Schottky barrier, nā LED polū-ʻōmaʻomaʻo a me nā lasers ultraviolet.
I ka hōʻuluʻulu manaʻo, ʻoiai he mau epitaxy heterogeneous nā substrates epitaxial GaN i hoʻohana pinepine ʻia, ke kū nei lākou a pau i nā pilikia maʻamau e like me ka mismatch lattice a me nā ʻokoʻa nui i nā coefficients hoʻonui thermal i nā kekelē like ʻole. Ua kaupalena ʻia nā substrates epitaxial GaN homogeneous e ka oʻo ʻana o ka ʻenehana, a ʻaʻole i hana nui ʻia nā substrates. Kiʻekiʻe ke kumukūʻai hana, liʻiliʻi ka nui o ka substrate, a ʻaʻole kūpono ke ʻano o ka substrate. ʻO ka hoʻomohala ʻana o nā substrates epitaxial GaN hou a me ka hoʻomaikaʻi ʻana i ka maikaʻi epitaxial kekahi o nā mea nui e kāohi ana i ka hoʻomohala hou ʻana o ka ʻoihana epitaxial GaN.
IV. Nā ʻano hana maʻamau no ka epitaxy GaN
MOCVD (hoʻokomo mahu kemika)
Me he mea lā ʻo ka epitaxy homogeneous ma nā substrates GaN ke koho maikaʻi loa no ka epitaxy GaN. Eia nō naʻe, ʻoiai ʻo nā mea mua o ka waiho ʻana o ka mahu kemika he trimethylgallium a me ammonia, a ʻo ke kinoea lawe he hydrogen, ʻo ka mahana ulu MOCVD maʻamau ma kahi o 1000-1100 ℃, a ʻo ka wikiwiki o ka ulu ʻana o MOCVD ma kahi o kekahi mau microns i kēlā me kēia hola. Hiki iā ia ke hana i nā interfaces steep ma ka pae atomic, kahi kūpono loa no ka ulu ʻana o nā heterojunctions, nā lua quantum, nā superlattices a me nā ʻano hana ʻē aʻe. ʻO kona wikiwiki ulu, ka like maikaʻi, a me ke kūpono no ka ulu ʻana o ka wahi nui a me nā ʻāpana he nui e hoʻohana pinepine ʻia i ka hana ʻoihana.
MBE (epitaxy kukuna molekala)
I loko o ka epitaxy beam molecular, hoʻohana ʻo Ga i kahi kumu elemental, a loaʻa ka naikokene hana mai ka naikokene ma o ka plasma RF. Ke hoʻohālikelike ʻia me ke ʻano MOCVD, ʻoi aku ka haʻahaʻa o ka mahana ulu MBE ma kahi o 350-400℃. Hiki i ka mahana ulu haʻahaʻa ke pale aku i kekahi haumia i hiki ke hana ʻia e nā wahi wela kiʻekiʻe. Hana ka ʻōnaehana MBE ma lalo o ka vacuum ultra-high, kahi e hiki ai iā ia ke hoʻohui i nā ʻano ʻike in-situ hou aʻe. I ka manawa like, ʻaʻole hiki ke hoʻohālikelike ʻia kona wikiwiki ulu a me ka hiki ke hana me MOCVD, a hoʻohana nui ʻia ia i ka noiʻi ʻepekema [7].
Kiʻi 5 (a) Eiko-MBE schematic (b) MBE nui reaction chamber schematic
Ke ʻano hana HVPE (epitaxy pae mahu hydride)
ʻO nā mea mua o ke ʻano hana epitaxy pae mahu hydride ʻo GaCl3 a me NH3. Ua hoʻohana ʻo Detchprohm et al. i kēia ʻano hana e ulu ai i kahi papa epitaxial GaN he mau haneli microns ka mānoanoa ma luna o ka ʻili o kahi substrate sapphire. I kā lākou hoʻokolohua, ua ulu ʻia kahi papa o ZnO ma waena o ka substrate sapphire a me ka papa epitaxial ma ke ʻano he papa buffer, a ua ʻili ʻia ka papa epitaxial mai ka ʻili o ka substrate. Ke hoʻohālikelike ʻia me MOCVD a me MBE, ʻo ka hiʻohiʻona nui o ke ʻano HVPE ʻo ia kona wikiwiki ulu kiʻekiʻe, kūpono no ka hana ʻana i nā papa mānoanoa a me nā mea nui. Eia nō naʻe, i ka wā e ʻoi aku ai ka mānoanoa o ka papa epitaxial ma mua o 20μm, ua maʻalahi ka papa epitaxial i hana ʻia e kēia ʻano hana i nā māwae.
Ua hoʻolauna ʻo Akira USUI i ka ʻenehana substrate patterned e pili ana i kēia ʻano hana. Ua ulu mua lākou i kahi papa epitaxial GaN lahilahi 1-1.5μm mānoanoa ma kahi substrate sapphire me ka hoʻohana ʻana i ke ʻano MOCVD. ʻO ka papa epitaxial he papa buffer GaN mānoanoa 20nm i ulu ʻia ma lalo o nā kūlana mahana haʻahaʻa a me kahi papa GaN i ulu ʻia ma lalo o nā kūlana mahana kiʻekiʻe. A laila, ma 430 ℃, ua uhi ʻia kahi papa o SiO2 ma luna o ka ʻili o ka papa epitaxial, a ua hana ʻia nā kaha puka makani ma ke kiʻiʻoniʻoni SiO2 e ka photolithography. ʻO ka mamao o ke kaha he 7μm a ʻo ka laulā o ka mask mai 1μm a i 4μm. Ma hope o kēia hoʻomaikaʻi ʻana, ua loaʻa iā lākou kahi papa epitaxial GaN ma kahi substrate sapphire 2-ʻīniha ke anawaena i ʻole e haki a laumania e like me ke aniani ʻoiai ua piʻi ka mānoanoa i nā ʻumi a i ʻole nā haneli o microns. Ua hoʻemi ʻia ka nui o nā hemahema mai 109-1010cm-2 o ke ʻano HVPE kuʻuna a hiki i kahi 6 × 107cm-2. Ua kuhikuhi pū lākou ma ka hoʻokolohua i ka wā e ʻoi aku ai ka nui o ka ulu ʻana ma mua o 75μm/h, e lilo ka ʻili o ka laʻana i ʻinoʻino [8].
Kiʻi 6 Kiʻikuhi Kiʻi o ka Substrate
V. Hōʻuluʻulu Manaʻo a me ka Nānā
Ua hoʻomaka ka puka ʻana mai o nā mea GaN i ka makahiki 2014 i ka wā i lanakila ai ka LED kukui polū i ka Nobel Prize ma Physics i kēlā makahiki, a ua komo i loko o ke kahua o ka lehulehu o nā noi hoʻouka wikiwiki ma ke kahua o nā mea uila mea kūʻai. ʻO ka ʻoiaʻiʻo, ua puka mālie mai nā noi i nā mea hoʻoikaika mana a me nā mea RF i hoʻohana ʻia ma nā kikowaena kumu 5G i ʻike ʻole ʻia e ka hapa nui o ka poʻe. I nā makahiki i hala iho nei, ua manaʻo ʻia ka holomua o nā mea mana kaʻa GaN e wehe i nā wahi ulu hou no ka mākeke noi mea GaN.
ʻO ka nui o ke koi o ka mākeke e paipai maoli i ka hoʻomohala ʻana o nā ʻoihana a me nā ʻenehana e pili ana iā GaN. Me ka oʻo a me ka hoʻomaikaʻi ʻana o ke kaulahao ʻoihana e pili ana iā GaN, e hoʻomaikaʻi ʻia a lanakila ʻia paha nā pilikia e kū nei i ka ʻenehana epitaxial GaN o kēia manawa. I ka wā e hiki mai ana, e hoʻomohala maoli ka poʻe i nā ʻenehana epitaxial hou aʻe a me nā koho substrate maikaʻi loa. I kēlā manawa, hiki i ka poʻe ke koho i ka ʻenehana noiʻi waho kūpono loa a me ka substrate no nā hiʻohiʻona noi like ʻole e like me nā ʻano o nā hiʻohiʻona noi, a hana i nā huahana i hoʻokūkū ʻia.
Ka manawa hoʻouna: Iune-28-2024