Unusual compositional dependence of the Unusual compositional - PowerPoint PPT Presentation

Unusual compositional dependence of the Unusual compositional dependence of the exciton reduced mass exciton reduced mass it it d d d d in GaAs 1 x Bi x ( x =0 ‐ 10%) in GaAs 1 x Bi x ( x =0 ‐ 10%) x ( x ( ) ) 1 ‐ x 1 ‐ x G Pettinari 1 A Polimeni 2 J H Blokland 1 R Trotta 2 G. Pettinari 1 , A. Polimeni 2 , J. H. Blokland 1 , R. Trotta 2 , P. C. M. Christianen 1 , M. Capizzi 2 , J. C. Maan 1 , X Lu 3 E C Young 3 and T Tiedje 3 X. Lu , E. C. Young and T. Tiedje 1 High Field Magnet Laboratory, Radboud University Nijmegen, The Netherlands Radboud University Nijmegen, The Netherlands 2 Dipartimento di Fisica, Sapienza Università di Roma, Italy 3 Department of Physics and Astronomy, University of British Columbia, Vancouver, Canada Ann Arbor, July 16 th

Outline Bismuth in GaAs: ‐ electronic properties ‐ magneto ‐ photoluminescence (0 ‐ 30 T) and exciton reduced mass determination exciton reduced mass determination ‐ evidence for a largely perturbed band structure ‐ evidence for a largely perturbed band structure

Ga(As,Bi) expected trends atomic electronegativity electronegativity number first ionization CBs potential V 6 p Bi Bi is expected to III B V B 4 p As p s electron influence the configuration 3.04 4 s Ga 14.5 valence band B N 2 s N VBs 1s 2 2s 2 p 3 Al P 2.18 1.81 .8 9.81 6.00 Ga As Large relativistic corrections are [Ar]3d 10 4s 2 p 1 [Ar]3d 10 4s 2 p 3 expected due to Z → expected due to Z Bi → In Sb large SO splitting ∆ 0 of VB anion p ‐ states 2.02 7.29 ∆ (G Bi) 2 15 V ∆ 0 (GaBi)=2.15 eV Tl Tl Bi Bi [Xe]4f 14 5d 10 6s 2 p 3 P. Carrier and S. ‐ H. Wei, Phys. Rev. B 70 , 035212 (2004)

Ga(As,Bi) expected trends A. Janotti, S. ‐ H. Wei, and S. B. Zhang, Phys. Rev. B 65 , 115203 (2002) Predicted E g = ‐ 1.45 eV for GaBi Predicted E = ‐ 1 45 eV for GaBi density functional formalism and LDA (64 ‐ atom cell calculation) Expected band gap reduction following GaBi (heavier anion) (smaller gap) rule (heavier anion) ‐ (smaller gap) rule Γ L X Y. Zhang, A. Mascarenhas, and L. –W. Wang, Phys. Rev. B 71 , 155201 (2005) E Bi E Bi VBM VBM • Localization of valence band states at Bi L li ti f l b d t t t Bi atoms • Bi generates an impurity state ( E Bi ) 80 meV below the VBM • Pressure coefficient of E Bi similar to GaAs, no Bi state emerging from the VB density functional formalism and LDA

Ga(As,Bi) observed trends = + − − − E x E ( 1 x ) E b x ( 1 x ) GaAs 1- x Bi x GaAs 1 Bi GaBi GaAs − 1.40 x x T =290 K = α + β = − α = β = b ( x ) ( 1 x ) E 0 . 36 eV 9 . 5 eV 10 . 4 GaBi Kunishige Oe and Hiroshi Okamoto, Jpn. J. Appl. Phys. 37 , L1283 (1998) (eV) 1.20 X. Lu et al. , Appl. Phys. Lett. 95 , 41903 (2009) X. Lu et al. , Appl. Phys. Lett. 95 , 41903 (2009) Energy x =(0 ‐ 5)% ∆ E g ≈‐ 80 meV/%Bi 1.00 (GaAs 1 ‐ x N x ; ∆ E g ≈ -100 meV/%N; b ~16-20 eV ) experiment (PL) experiment (PL) 0.800 0 2 4 6 8 10 12 x (%) 1.44 In z Ga 1- z As A larger band gap reduction is observed 1.28 y (eV) for the same increase in lattice constant GaAs GaAs 1- y N y N z =24% nd gap Energ 1.12 GaAs 1- w Sb w y =5% w =22% Potential for 0 96 0.96 GaAs GaAs 1- x Bi x Bi 1.31 µ m 1 31 µ m Ban • Heterojunction bipolar transistors GaAs • Solar cells x =10% 0.8 1.55 µ m • Telecom 5 6 5.6 5 65 5.65 5 7 5.7 5 75 5.75 a (Å)

Ga(As,Bi) observed trends B. Fluegel et al. , Phys. Rev. Lett. 97 , 067205 (2006) ∆ = ∆ + − ∆ − − GaBi GaAs ( GaAs Bi ) x ( 1 x ) b x ( 1 x ) − 0 1 x x 0 0 ∆ ∆ = ∆ ∆ = GaBi GaAs 2 2 . 15 15 eV eV 0 0 . 34 34 eV eV 0 0 0 0 b = ‐ 6.0 eV (GaAs 1 ‐ x N x ; ∆ 0 constant) Potential for spintronics Bi ‐ related states form with pressure coefficient similar to GaAs Ultrafast photoresponse in the NIR for emitters and detectors of pulsed THz radiation K. Bertulis et al. , Appl. Phys. Lett. 88 , 201112 (2006) S. Francoeur et al. , Phys. Rev. B 77 , 085209 (2008)

Ga(As,Bi): what about the carrier mass? J. Wu et al. , J. Appl. Phys. 105 , 011101 (2009) R. N. Kini et al. , J. Appl. Phys., 106 , 043705 (2009) Bi incorporation affects the electron mobility We address the carrier effective mass in Ga(As,Bi) b by magneto ‐ photoluminescence t h t l i

The samples Grown on (100) GaAs by molecular beam epitaxy Grown on (100) GaAs by molecular beam epitaxy FE GaAs 1- x Bi x x = 10.6% x =0, 0.6, 1.3, 1.7, 1.9, 3.0, 3.8, T = 200 K 4 5 5 6 8 5 and 10 6% 4.5, 5.6, 8.5 and 10.6% x = 8.5% 8 % T G =(270 – 380) °C, thickness t =(40 ‐ 350) nm x = 5.6% b. units) x = 4.5% X. Lu et al. , Appl. Phys. Lett. 92 , 192110 (2008) x = 3 8% x = 3.8% ensity (arb x = 3% PL Inte x = 1.9% x = 1.7% x = 1.3% LE x = 0.6% Good structural properties d l 0.8 1.0 1.2 1.4 Energy (eV)

The samples Grown on (100) GaAs by molecular beam epitaxy Grown on (100) GaAs by molecular beam epitaxy FE GaAs 1- x Bi x x = 10.6% x =0, 0.6, 1.3, 1.7, 1.9, 3.0, 3.8, T = 200 K 4.5, 5.6, 8.5 and 10.6% 4 5 5 6 8 5 and 10 6% x = 8.5% 8 % T G =(270 – 380) °C, thickness t =(40 ‐ 350) nm x = 5.6% b. units) x = 4.5% x = 3 8% x = 3.8% 110 110 ensity (arb T =200 K M (meV) x = 3% 90 FWHM PL Inte x = 1.9% 70 x = 1.7% 50 0 2 4 6 8 10 x = 1.3% x (%) LE x = 0.6% Unusual compositional linewidth dependence Unusual compositional linewidth dependence 0.8 1.0 1.2 1.4 Energy (eV)

High ‐ magnetic field measurements Nijmegen The Netherlands B = 0 – 33 T ‐ Powered by 2×10 MW at 500 V (4 ⋅ 10 4 A) ‐ Chilled by 10 4 l/min deionised water at 30 atm at 10 ° C. 1 hour magnet time costs 1,000 €

Why 200 K? GaAs 1- x Bi x GaAs 1- x Bi x FE FE T =210 K x =1.9% x 1.9% x 8.5% x =8.5% T = 200 K nits) nits) P =12 P 0 P =20 P P =20 P 0 0 nsity (arb. un nsity (arb. un P = 4 P 0 P = 10 P 0 P =P 0 P = 2 P 0 LE P = P PL Inten LE PL Inten 0 T = 10 K T =10 K P =20 P 0 0 P 12 P P =12 P 0 P = 10 P 0 P = 4 P 0 P = 2 P 0 P = P 0 P = P 0 1.15 1.2 1.25 1.3 1.35 1.4 0.8 0.85 0.9 0.95 1 1.05 Energy (eV) Energy (eV) Localized excitons dominate low ‐ T photoluminescence p G. Pettinari et al. , Appl. Phys. Lett. 92 , 262105 (2008)

Why 200 K? GaAs 1- x Bi x - x = 0.6% GaAs 1- x Bi x - x = 1.9% GaAs 1- x Bi x - x = 5% (3.6%) 4.5% (a) (b) (c) units) P 0 = 8 W/cm 2 P 0 = 8 W/cm 2 P 0 = 8 W/cm 2 ensity (arb. 16× P 0 16× P 0 16× P 0 T = 180 K T = 180 K T = 180 K 3× P 0 3× P 0 3× P 0 FE FE FE LE P 0 P 0 P 0 ized PL Inte FE GaAs 16× P 0 16× P 0 16× P 0 Normali T = 150 K T = 150 K T = 150 K 3× P 0 3× P 0 3× P 0 P 0 P 0 FE P 0 LE LE FE LE FE 0.25× P 0 0.05× P 0 0.25× P 0 0 0 0 1.2 1.3 1.4 1.5 1.0 1.1 1.2 1.3 1.4 1.0 1.1 1.2 1.3 Energy (eV) Energy (eV) Energy (eV) Accurate choice of measurement power and temperature p p

Why 200 K? R K d R. Kudrawiec et al. , J. Appl. Phys. 106 , 023518 (2009) i l J A l Ph 106 023518 (2009) S I h f S. Imhof et al. , Appl. Phys. Lett. 96 , 131115 (2010) l A l Ph L 96 131115 (2010) x =4.5% x =3%

Magneto ‐ PL: data 2 2 P =10 W/cm P =70 W/cm GaAs 1- x Bi x GaAs 1- x Bi x At high power carrier T =190 K T =190 K x =8.5% x =8.5% scattering disrupts g p 30 T 30 T 30 T 30 T the coherence of the electron/hole b. un.) cyclotron orbit cyclotron orbit ntensity (arb PL In 0 T 0 T 0.80 0.85 0.90 0.95 1.00 1.05 0.80 0.85 0.90 0.95 1.00 1.05 Energy (eV) Energy (eV) Energ (eV) Energy (eV) G Pettinari et al Phys Rev B 81 235211 (2010) G. Pettinari et al ., Phys. Rev. B 81 , 235211 (2010)

Magneto ‐ PL: data 0.95 2 P 0 = ~10 W/cm At high power carrier 3×P 0 scattering disrupts g p 0 Energy (eV) 7×P 0 the coherence of the 0.94 15×P 0 electron/hole cyclotron orbit cyclotron orbit PL Peak E 0.93 T = 190 K T 190 K GaAs 1- x Bi x - x = 8.5% 0.92 0 6 12 18 24 30 B (T) B (T) G Pettinari et al Phys Rev B 81 235211 (2010) G. Pettinari et al ., Phys. Rev. B 81 , 235211 (2010)

Magneto ‐ PL: data GaAs:Si ( e ,A) At high power carrier T =5 K Si =10 18 cm -3 bb n scattering disrupts g p 30T the coherence of the 28T 26T electron/hole units) 24T cyclotron orbit cyclotron orbit 22T 22T tensity (arb. u 20T as found in 18T degenerate GaAs 16T 14T and InN and InN PL Int 12T 10T 1.54 08T µ = 0.049 m 0 06T 04T 1.53 ergy (eV) LL 0 02T 00T ( e ,A) 1.42 1.46 1.5 1.54 1.58 1.52 Energy (eV) Energy (eV) Ene 1.51 m e = 0.069 m 0 G Pettinari et al Phys Rev B 79 165207 (2009) G. Pettinari et al ., Phys. Rev. B 79 , 165207 (2009) 0 10 20 30 B (T)

Magneto ‐ PL: data 17 cm -3 InN n=4 × 10 At high power carrier T = 5K 30T scattering disrupts g p the coherence of the electron/hole cyclotron orbit cyclotron orbit as found in degenerate GaAs and InN and InN 10T 682 08T 06T ergy (meV) µ = 0.093 m 0 04T 678 02T 00T Ene 674 600 620 640 660 680 700 720 Energy(meV) 670 0 8 16 24 32 G. Pettinari et al ., Phys. Rev. B 79 , 165207 (2009) B (T)

Magneto ‐ PL: data . . . back to GaAsBi GaAs 1- x Bi x - x = 0.6% T = 200 K GaAs 1 Bi 15 15 1- x x x = 0.6% free T = 200 K units) exciton B = 30 T 10 10 sity (arb. u 27 T E d (meV) 24 T 21 T 18 T 5 5 ∆ E 15 T PL Inten 12 T localized 09 T exciton 06 T 0 FE FE LE 03 T 00 T 0 6 12 18 24 30 FE GaAs B (T) 1.2 1.3 1.4 1.5 E Energy (eV) ( V) Localized excitons behave differently