Binciken Tsarin Kwayoyin Halitta na Tazarar Kore a cikin InGaN/GaN LEDs: Matsayin Saurin Gaurayawan Alloy na Bazuwar

1. Gabatarwa & Matsalar Tazarar Kore

III-nitride InGaN/GaN-based fitilun fitilun haske (LEDs) suna wakiltar kololuwar inganci don hasken wuta mai ƙarfi (SSL), tare da blue LEDs waɗanda suka wuce 80% ingancin canjin wutar lantarki. Hanyar da ta fi yawa don samar da farin haske ta ƙunshi amfani da phosphor don rage fitar da hasken blue LED, wani tsari da ke haifar da asarar Stokes (~25%). Don cimma iyakar inganci ta ƙarshe, hanyar haɗa launi kai tsaye ba tare da phosphor ba, ta amfani da LEDs ja, kore, da shuɗi (RGB) yana da mahimmanci. Duk da haka, wannan dabarar tana fuskantar matsalar "tazarar kore" - raguwa mai tsanani da tsari a cikin ingancin ƙididdiga na waje (EQE) na LEDs masu fitar da haske a cikin bakan kore-zuwa-rawaya (kimanin 530-590 nm) idan aka kwatanta da na blue da ja.

Wannan aikin ya nuna cewa babban mai ba da gudummawa ga wannan raguwar inganci a cikin c-plane InGaN/GaN quantum well (QW) LEDs shine saurin bazuwar na asali na atom ɗin Indiyum (In) a cikin gaurayawan InGaN. Yayin da abun ciki na In ya ƙaru don canza fitarwa daga blue zuwa tsayin raƙuman kore, waɗannan saurin sun zama mafi bayyanawa, suna haifar da ƙaruwar tsayawa wuri na masu ɗaukar kaya da kuma raguwar ma'aunin haɗuwar haske.

2. Hanyar Aiki: Tsarin Simintin Tsarin Kwayoyin Halitta

Don ware tasirin rashin daidaituwar alloy daga wasu sanannun dalilai kamar tasirin quantum-confined Stark (QCSE) ko lahani na kayan aiki, marubutan sun yi amfani da tsarin simintin tsarin kwayoyin halitta.

2.1 Tsarin Simintin

Tsarin lantarki na tsarin InGaN/GaN QW an ƙididdige shi ta amfani da hanyar ɗaure mai ƙarfi ko hanyar pseudopotential na gogewa a matakin kwayoyin halitta. Wannan hanyar tana lissafin saitin bazuwar na atom ɗin In da Ga akan sublattice na cation, tana motsawa bayan kiyasi na al'ada na kankara (VCA) wanda ke ɗaukan cikakkiyar gaurayawan alloy.

2.2 Ƙirƙirar Saurin Gaurayawan Alloy na Bazuwar

An samar da daidaitattun tsarin atom ɗin bazuwar da yawa don wani matsakaicin abun ciki na Indiyum (misali, 15%, 25%, 35%). Ga kowane tsari, an ƙididdige yanayin yuwuwar gida, ayyukan tsinkaya na lantarki da rami, da kuma juna. Binciken ƙididdiga a cikin daidaitattun tsari da yawa ya ba da matsakaicin hali da rarraba mahimman ma'auni kamar yawan haɗuwar haske.

3. Sakamako & Bincike

3.1 Ma'aunin Haɗuwar Haske vs. Abun ciki na Indiyum

Babban binciken shine cewa ma'aunin haɗuwar haske (B) yana raguwa sosai tare da ƙaruwar matsakaicin abun ciki na Indiyum a cikin QW. Simintin sun nuna cewa wannan sakamako ne kai tsaye na saurin alloy. Babban abun ciki na In yana haifar da ƙaruwar saurin yuwuwar, yana haifar da ƙaruwar rabuwa ta sarari tsakanin ayyukan tsinkaya na lantarki da rami.

3.2 Matsakaicin Aikin Tsinkaya da Tsayawa Wuri

Simintin tsarin kwayoyin halitta suna ganin tsayawa wuri na masu ɗaukar kaya. Lantarki da ramukan suna son kasancewa cikin tarko a cikin ƙananan yuwuwar gida waɗanda yankuna na ɗan ƙaramin yawan In (don ramukan) da bambance-bambancen damuwa/ yuwuwar da suka dace (don lantarki) suka haifar. Haɗin haɗin kai $\Theta = \int |\psi_e(r)|^2 |\psi_h(r)|^2 dr$ , wanda yake daidai da yawan haske, an gano yana raguwa yayin da waɗannan jihohin da aka tsaya suka zama mafi rabuwa ta sarari tare da manyan saurin In.

3.3 Kwatantawa da Sauran Dalilai (QCSE, Lalacewa)

Takardar ta yarda cewa QCSE (wanda ƙaƙƙarfan filayen polarization a cikin c-plane nitrides ke haifarwa) da ƙaruwar yawan lahani a babban abun ciki na In suma suna lalata inganci. Duk da haka, simintin tsarin kwayoyin halitta suna nuna cewa ko da ba tare da waɗannan ƙarin dalilai ba, rashin daidaituwar alloy na asali shi kaɗai zai iya lissafin babban ɓangaren "tazarar kore" da aka gani ta hanyar rage yawan haske na asali.

4. Cikakkun Bayanai na Fasaha & Tsarin Lissafi

Yawan haɗuwar haske don canji ana bayar da shi ta Dokar Zinariya ta Fermi: $$R_{spon} = \frac{4\alpha n E}{3\hbar^2 c^2} |M|^2 \rho_{red}(E) f_e(E) f_h(E)$$ inda $|M|^2$ shine murabba'in matrix element na motsi, $\rho_{red}$ shine rage yawan jihohi, kuma $f_e$, $f_h$ ayyukan Fermi ne. Babban tasirin saurin alloy yana kan matrix element $|M|^2 \propto \Theta$, matsakaicin aikin tsinkaya. Lissafin tsarin kwayoyin halitta yana maye gurbin matsakaicin $\Theta$ daga VCA tare da matsakaicin tarin bazuwar tsari: $\langle \Theta \rangle_{config} = \frac{1}{N} \sum_{i=1}^{N} \Theta_i$, wanda aka nuna yana raguwa tare da abun ciki na In.

5. Mahallin Gwaji & Bayanin Ginshiƙi

Takardar tana nuni zuwa ginshiƙi na gwaji na yau da kullun (wanda aka nuna a matsayin Fig. 1) wanda ke nuna Ingantaccen Ƙididdiga na Waje (EQE) vs. tsayin raƙuman fitarwa don LEDs na zamani. Wannan ginshiƙin zai nuna:

• Babban kololuwa (~80%) a yankin blue (450-470 nm) don InGaN LEDs.
• Ragewar EQE ta cikin yankin kore (520-550 nm) da rawaya (570-590 nm), yana faɗuwa yuwuwar ƙasa da 30%.
• Dawo da inganci a yankin ja (>620 nm) don AlInGaP-based LEDs.
• "Tazarar kore" a zahiri ita ce rami mai zurfi tsakanin kololuwar InGaN blue da kololuwar AlInGaP ja.

Sakamakon simintin don ma'aunin haske $B$ zai yi daidai da wannan yanayin, yana ba da bayanin kimiyyar lissafi na asali don gefen hagu (na tushen nitride) na wannan kwarin inganci.

6. Tsarin Bincike: Nazarin Lamari

Lamari: Kimanta Sabon Girka na Green LED Epitaxy
Wani masana'anta ya haɓaka sabon girka na girma na MOCVD yana da'awar rage "tazarar kore." Ta amfani da tsarin daga wannan takarda, manazarta zai:

1. Ware Mai Canzawa: Siffanta sabon tsarin na matsakaicin abun ciki na In da faɗin rijiyar. Yi amfani da babban ƙididdiga na X-ray diffraction (HRXRD) da photoluminescence (PL).
2. Kimanta Daidaiton Alloy: Yi amfani da atom probe tomography (APT) ko scanning transmission electron microscopy (STEM) tare da taswirar EDS don ƙididdige ma'auni da girman saurin abun ciki na In. Kwatanta da samfuran daidaitattun.
3. Ƙirƙirar Tasirin: Shigar da ƙididdiga na saurin da aka auna cikin mai warware ɗaure mai ƙarfi na tsarin kwayoyin halitta (kamar NEMO ko daidai) don ƙididdige yiwuwar matsakaicin aikin tsinkaya $\langle \Theta \rangle$ da ma'aunin haske $B$.
4. Raba daga QCSE/Lalacewa: Auna ingancin PL na ƙananan zafin jiki da PL mai lokaci don kimanta gudummawar dangi na yawan haske vs. marasa haske. Yi amfani da ma'aunin piezoelectric don kimanta filin ciki.
5. Hukunci: Idan sabon girka ya nuna rage saurin kuma ƙirar $B$ ta ƙaru, haɓakar yana yiwuwa ta asali ne. Idan ba haka ba, kowane ribar inganci na iya kasancewa saboda rage lahani ko gyare-gyaren filayen, waɗanda ke da iyakokin iyawa daban-daban.

7. Cikakkiyar Fahimta & Ra'ayi na Manazarta

Cikakkiyar Fahimta: "Tazarar kore" ba kawai matsala ce ta injiniya ba; matsala ce ta kimiyyar lissafi ta kayan aiki da aka gasa cikin yanayin gaurayawan alloy na InGaN. Wannan takarda tana ba da hujja mai ƙarfi cewa ko da tare da cikakkun lu'ulu'u da filayen polarization sifili, ƙididdigar tarin atom ɗin Indiyum a zahiri tana rage yawan haske yayin da muke tuƙa don tsayin raƙuman raƙuman. Wannan yana canza labarin daga neman rage yawan lahani kawai zuwa sarrafa rashin daidaituwar alloy a matakin atom.

Tsarin Ma'ana: Hujjar tana da kyau kuma ta bi tsari: 1) Haɗa launi yana buƙatar ingantattun masu fitar da kore. 2) Fitar da kore yana buƙatar babban abun ciki na In InGaN. 3) Babban abun ciki na In yana nufin ƙaƙƙarfan saurin abun ciki. 4) Saurin yana tsayawa masu ɗaukar kaya kuma yana rage matsakaicin aikin tsinkaya. 5) Rage matsakaicin yana yanke ma'aunin haske, yana haifar da tazarar. Yana raba wannan iyaka na asali daga abubuwan waje kamar QCSE.

Ƙarfi & Kurakurai: Ƙarfin yana cikin hanyar aiki—amfani da simintin tsarin kwayoyin halitta don duba ƙarƙashin labulen VCA yana da ƙarfi da gamsarwa, yana daidaitawa da yanayin sauran tsarin da ba su da tsari kamar perovskite LEDs. Laifin, wanda marubutan suka yarda da shi, shine ware wannan maɓalli guda ɗaya. A cikin na'urori na gaske, rashin daidaituwar alloy, QCSE, da lahani suna haifar da haɗin kai mai cutarwa. Ƙirar takardar tana yiwuwa ta ƙima cikakkiyar tsananin tazarar saboda ba ta haɗa waɗannan tasirin gaba ɗaya ba; misali, jihohin da aka tsaya na iya zama mafi saukin kamuwa da haɗuwar mara haske a lahani, wani batu da aka bincika a cikin ayyukan baya kamar na ƙungiyar Speck ko Weisbuch.

Fahimta Mai Aiki: Ga masana'antun LED, wannan binciken kira ne na ƙyale don matsawa bayan kawai auna matsakaicin abun ciki da kauri. Metrology don ƙididdiga na sauri dole ne ya zama daidaitaccen. Dabarun girma yakamata su yi niyya ba kawai don babban haɗin In ba amma don rarrabawar sa daidai. Dabarun kamar gaurayawan dijital (superlattices na gajeren lokaci), girma a ƙarƙashin yanayi da aka gyara (misali, babban zafin jiki tare da surfactants), ko amfani da abubuwan da ba su da ƙarfi/rabin ƙarfi don cire QCSE da mafi kyawun bayyana iyakar iyakar alloy, sun zama mahimman hanyoyin ci gaba. Taswirar zuwa SSL mai inganci yanzu a fili ya haɗa da "injiniyan alloy" a matsayin muhimmin mataki.

8. Aikace-aikace na Gaba & Hanyoyin Bincike

• Girma Mai Kula da Metrology: Haɗa saka idanu na abun ciki a cikin-situ da sarrafa amsawa na ainihi yayin girma na MOCVD/MBE don hana tarin In.
• Gaurayawan Dijital & Tsarukan da aka Tsara: Bincika gajeren lokaci na InN/GaN superlattices a matsayin madadin gaurayawan bazuwar don samar da tsarin lantarki mai ƙayyadaddun ƙayyadaddun bayanai.
• Madadin Matsayin Abubuwan da ake amfani da su: Haɓaka ci gaban LEDs akan marasa ƙarfi (m-plane, a-plane) ko jirage masu rabin ƙarfi (misali, (20-21)) don kawar da QCSE. Wannan zai ba da damar kimantawa da niyya mafi kyau na iyakar saurin alloy mai tsafta.
• Simintin Ci-gaba: Haɗa tsarin lantarki na tsarin kwayoyin halitta tare da ƙira na'ura na gudun hijira-diffusion ko Monte Carlo don hasashen cikakkiyar ingancin LED a ƙarƙashin yanayin aiki na gaske, gami da hulɗar rashin tsari, polarization, da lahani.
• Bayan Hasken Wuta: Fahimta da sarrafa saurin alloy kuma yana da mahimmanci ga aikin diodes Laser (LDs) na InGaN na kore don masu tsinkaya, sadarwar haske mai iya gani (Li-Fi), da fasahohin ƙididdiga.

9. Nassoshi

1. S. Nakamura, T. Mukai, M. Senoh, "Candela-class high-brightness InGaN/AlGaN double-heterostructure blue-light-emitting diodes," Appl. Phys. Lett., vol. 64, no. 13, pp. 1687–1689, 1994. (Nassoshi na nasara na 1993).
2. M. R. Krames et al., "Status and Future of High-Power Light-Emitting Diodes for Solid-State Lighting," J. Disp. Technol., vol. 3, no. 2, pp. 160–175, 2007.
3. B. D. Piercy, "The Case for a Phosphor-Free LED Future," Compound Semiconductor Magazine, vol. 24, no. 5, 2018. (Misalin ra'ayi na masana'antu akan haɗa launi).
4. E. F. Schubert, Light-Emitting Diodes, 3rd ed. Cambridge University Press, 2018. (Littafin malami mai iko akan kimiyyar lissafi na LED).
5. J. Piprek, "Efficiency Drop in Green InGaN/GaN Light-Emitting Diodes: The Role of Random Alloy Fluctuations," Proc. SPIE 9768, 97681M, 2016. (Wani bita mai alaƙa, na gaba).
6. U.S. Department of Energy, "Solid-State Lighting R&D Plan," 2022. (Taswirar hanya ta hukuma da ke nuna ƙalubalen tazarar kore).
7. A. David et al., "The Physics of Recombination in InGaN Quantum Wells," in Nitride Semiconductor Light-Emitting Diodes (LEDs), Woodhead Publishing, 2018. (Cikakken tattaunawa akan hanyoyin haske da marasa haske).