Non-equilibrium metalorganic vapour phase epitaxy and optical spectroscopy of the band formation and band structure of metastable compound semiconductors
Zusammenfassung der Projektergebnisse
Heterostructures based on the novel, dilute-nitride direct band gap Ga(NAsP)-laser material, which can be grown lattice-matched to (001) Si-substrates, have recently been introduced in order to monolithically integrate novel optoelectronic and photonic components to Si-based micro- and nanoelectronic circuits in the future. The present project has supported this very challenging long-term goal by studying and optimizing Ga(NAsP)/(BGa)(AsP)-multiquantum well heterostructures (MQWH). The non-equilibrium metalorganic vapour phase epitaxy (MOVPE) applying efficiently decomposing MO-group-V-source molecules has been concentrating on epitaxially grown III/(NV)-mixed crystalline layers and heterostructures in the GaP-based active penternary (GaIn)(NAsP)-multiple quantum well heterostructures (MQWH) with various barrier configurations in the (BGa)(AsP)-material system. The influence of adding Sb as a surfactant during MOVPE growth of Ga(NAsP) has been investigated. While for the deposition on GaP-substrate a clear improvement in epitaxial layer quality ( reduced interface roughness, reduced photoluminescence (PL) linewidth and increased PL efficiency) has been verified, the situation for growth on Si-substrate, however, is less clear. Additional investigations are underway to clarify this behaviour. The epitaxial deposition of (BGa)(AsP)-barrier layers has been studied as a function of growth temperature, B/III- as well as As/V-ratios. The B-incorporation efficiency is drastically different for (BGa)P and (BGa)As. The key parameter for B-incorporation in the quaternary (BGa)(AsP) is the As/V-ratio. Disorder induced effects of the optoelectronic properties of Ga(NAsP)/(BGa)(AsP-MQWH have been studied in detail by temperature-dependent PL-analysis also in comparison to theoretical modelling. Two scales of siorder have been found. One disorder scale relates to the ntrnsic compositional fluctuations due to the statistical incorporation of N in Ga(NAsP), while the other one relates to sample inhomogeneities resulting from long range fluctuations of the well width or of compositional inhomogeneities resulting from non-optimized growth conditions, respectively. The experimentally observed reduction in alloy disorder with increasing N-content has been modelled theoretically. The band structure of the B-containing barrier layers as a function of chemical composition has been verified by means of optical spectroscopy techniques. The type-I-band alignment as well as the energetic alignment of higher lying Ga(NAsP) quantum well states with the X-states of the chosen (BGa)(AsP)-barriers has been studied by PL excitation spectroscopy. Based on these studies Ga(NAsP)/(BGa(AsP)-based laser structures have been deposited on GaP- as well as Si-substrates and have subsequently been processed into broad area laser devices. Ga(NAsP)-based electrical injection lasers on GaP-substrate at room temperature and on Si-substrate at reduced temperature have been realized. Detailed analysis of the laser characteristics by means of pressure- and temperature-dependent studies clearly point to leakage currents as the major source for the efficiency limitations of Ga(NAsP)-based lasers at present. All of these results clearly point to the successful research of this project in conjunction with partner activities and the enormous potential for applications for monolithically integrated Ga(NAsP)-laser with Si based micro- and nanoelectronic circuits in the near future.
Projektbezogene Publikationen (Auswahl)
- Pecularities of the photoluminescence of metastable Ga(NAsP)/GaP quantum well structures. Phys. Rev. B82, 245309 (2010)
C. Karcher, K. Jandieri, B. Kunert, R. Fritz, M. Zimprich, K. Volz, W. Stolz, F. Gebhard, S.D. Baranovskii, W. Heimbrodt
- Band structure properties of novel BxGa1-xP alloys for silicon integration. J. Appl. Phys. 110, 063101 (2011)
N. Hossain, T.J.C. Hosea, S.J. Sweeney, S. Liebich, M. Zimprich, K. Volz, B. Kunert, W. Stolz
- Laser operation of Ga(NAsP) lattice-matched to (001) Si-substrate. Appl. Phys. Lett. 99, 071109 (2011)
S. Liebich, M. Zimprich, A. Beyer, K. Volz, B. Kunert, W. Stolz, C. Lange, S. Chatterjee, N. Hossain, S.J. Sweeney
- Vibrational mode and dielectric function spectra of BGaP probed by Raman scattering and spectroscopic ellipsometry. J. Appl. Phys. 109, 053504 (2011)
S. Rogowsky, M. Bäumler, M. Wolfer, L. Kirste, R. Ostendorf, J. Wagner, S. Liebich, W. Stolz, K. Volz, B. Kunert
- Energy scaling of compositional disorder in Ga(NPAs)/GaP quantum well structures. Phys Rev. B86, 125318 (2012)
K. Jandieri, M.K. Shakfa, S. Liebich, M. Zimprich, B. Kunert, C. Karcher, A. Chernikov, K. Volz, W. Stolz, M. Koch, S. Chatterjee, W. Heimbrodt, F. Gebhard, S.D. Baranovskii
(Siehe online unter https://doi.org/10.1103/PhysRevB.86.125318) - Growth of (BGa)As, (BGa)P, (BGa)(AsP) and ( BGaIn)P by MOVPE. J. Cryst. Growth 370, 191 (2013)
N. Sommer, R. Buss, T. Wegele, J. Ohlmann, B. Kunert, W. Stolz, K. Volz
(Siehe online unter https://doi.org/10.1016/j.jcrysgro.2012.07.035)
