N coordination chemistry in diluted InGaAs nitride layers
Abstract
GaAsN and InGaAsN semiconductor alloys with a small amount of nitrogen, so called dilute nitrides, constitute a novel compounds family with applications in telecom lasers and very efficient multijunction solar cells. The incorporation of N, which has a much larger electronegativity and smaller atomic size compared to As, induces a strong structural distortion in the InGaAs coordination chemistry, which will also affect the material electronic structure and band-gap. In particular, the nearest-neighbour bonding configuration of the N in InGaAsN has proven its influence on the band-gap. Our ARXPS results demonstrate that a higher growth temperature favour the formation of In-N bonds.
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Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA N coordination chemistry in diluted InGaAs nitride layers M. Gabás, M.C. López-Escalante, J.R. RamosBarrado The Nanotech Unit-Depto. Física Aplicada I University of Málaga Málaga, Spain B. Ściana, W. Dawidowski, D. Radziewicz Faculty of Microsystem Electronics and Photonics, Wrocław University of Technology, Wrocław, Poland P. Dłużewski Institute of Physics Polish Academy of Science Warsaw, Poland
Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA Motivation Lattice matched to GaAs Band gap tunability a0 (Å) Eg (eV) 1 eV Applications: promising material for IR lasers and HBT VCSELs and RCE devices high efficiency multi-junction solar cells - In0.09Ga0.91As0.97N0.03 lattice-matched to GaAs and Ge substrate Eg 1 eV Unusual properties: Technological problems: Huge band gap bowing coefficient Band gap reduction with small amount of N Large conduction band offset ( Ec > 300 meV) Large miscibility gap between GaAs and GaN Large amounts of point defects: vacances, antisites, interstitials High concentration of impurities: oxygen, carbon, hydrogen (MOVPE) Large amounts of examination methods are needed for proper characterisation Courtesy of Prof. M. Tłaczała
Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA Sample description Growth method AP MOVPE AIX200 RD Aixtron horizontal reactor organic sources: AsH3 (10% in H2), TMGa, TMIn, TBHy H2 as a carrier gas (100)-oriented n-doped GaAs substrate Growth parameters Organic source temperatures: TTMGa = - 10°C, TTMIn = 20°C, TTBHy = 30°C VAsH3 = 50 ml/ min (InGaAsN) Growth temperature: Tg = 575°C, 585°C Growth time: tg = 30 min, 10 min B. Ściana, et. al., Crystal Research and Technology, 47, 313 - 320 (2012) InyGa1-yAs1-xNx ~ 110 nm buffer GaAs ~ 0.3, 0.4 µm n-GaAs:Si substrate 35025 µm InyGa1-yAs1-xNx ~ 110 nm buffer GaAs ~ 0.3, 0.4 µm n-GaAs:Si substrate 35025 µm InyGa1-yAs1-xNx ~ 85 nm buffer GaAs ~ 0.3 µm n-GaAs:Si substrate 35025 µm NI52n NI52nA NI74n Annealing temperature and time: Tg = 700°C, tg = 5 min RTA process Tg = 575°C, tg = 30 min Tg = 585°C, tg = 10 min
Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA NI52n, NI52nA NI74n HRXRD -7000 -6000 -5000 -4000 -3000 -2000 -1000 0 1000 2000 3000 Omega/2Theta (s) 0.001 0.01 0.1 1 10 100 1K 10K 100K 1M counts/s NI74N_w2t004N.D01 symulacja4.Z00# simulation measurement measurement simulation Diffraction curves for the 004 reflection Reciprocal space maps for the 224 reflection fully relaxed 20% 0.1% ~ 80 nm In N 10% 0.48% In N ~ 30 nm 7% 0.72% 24% In N 0.2% ~ 20 nm 13% 0.3% In N ~ 85 nm 7% 0.5% fully strained
Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA Two-dimensional array of misfit dislocations in two perpendicular directions: [110] and [-110] Spectral range of the N-related local vibrational modes: visible modes connected with different N atoms configurations - NGa3In, NGa2In 2, NGa4 AFM Raman spectroscopy NI52n NI52n + NI74n
Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA SEM NI52n NI52nA NI74n • elongated bulges on the surface of NI52n samples (smaller on NI74n) • white nanometric spots on layer surfaces
STEM + HRTEM In As Ga InAs segregations Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA
Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA 600 500 400 300 200 100 0 BE (eV) NI74n XPS (a.u.) NI52n annealed NI52n Survey spectra O1s In3d C1s Ga LMM As3d Ga3d+In4d InxGa1-xAs1-yNy ARXPS N content very low y = 0.002-0.004 NI52n NI52nA NI74n 410 408 406 404 402 400 398 396 394 392 390 XPS (a.u.) 10º NI52n 45º BE (eV) 85º NI52n
Unidad de Nanotecnología - The Nanotech Unit - UNIVERSIDAD DE MALAGA ARXPS 410 408 406 404 402 400 398 396 394 392 390 BE (eV) XPS (a.u.) 85º N - In N - Ga 10º 45º precursor debris NI52n N 1s core level spectra • N – Ga bonds at surface • In content decreases as depth increases 410 408 406 404 402 400 398 396 394 392 390 XPS (a.u.) NI52n BE (eV) NI52n annealed • [N-In]/[N-Ga] increases after annealing, 1.3 1.5 NI52n NI52nA